Rockman : The Products - Rockman - By Tom Scholz

Rockman : The Products 

_____ 

Inside the Blue Box 

www.rockman.fr

TABLE OF CONTENTS 

THE POWER SOAK ............................................................................................................................... 3 

THE HEADPHONES AMPS.................................................................................................................... 7 

ROCKMOUNT, ROCKMAX AND ROCKBOX...................................................................................... 15 

THE ROCKMOUNT................................................................................................................................15 

THE ROCKMAX .................................................................................................................................... 17 

THE ROCKBOX .................................................................................................................................... 18 

THE ROCKMODULES.......................................................................................................................... 20 

SUSTAINOR ..................................................................................................................................... 21 

INSTRUMENT EQ............................................................................................................................. 27 

CHORUS/DELAY.............................................................................................................................. 31 

STEREO CHORUS ........................................................................................................................... 35 

STEREO ECHO ................................................................................................................................37 

GUITAR COMPRESSOR.................................................................................................................. 40 

SMART GATE ................................................................................................................................... 45 

DISTORTION GENERATOR ............................................................................................................ 49 

MIDI-OCTOPUS................................................................................................................................52 

DUAL REMOTE LOOP...................................................................................................................... 56 

THE XP SERIES ................................................................................................................................... 58 

THE PGE-2............................................................................................................................................ 63 

THE PRO-BASS ................................................................................................................................... 65 

AGP, UDG AND A12-50 ....................................................................................................................... 66 

ACCESSORIES .................................................................................................................................... 68 

STAGE GEAR....................................................................................................................................... 72 

APPENDICES ....................................................................................................................................... 73 

PRODUCTS LIST.............................................................................................................................. 74 

PRESS REVIEWS............................................................................................................................. 80 

© www.Rockman.fr 2008 Rockman Products reviews Page 2

Introduction 

THE POWER SOAK 

� The Power Soak was the first commercial product by Tom Scholz. It wasn't named "Rockman": this 

trademark was introduced only in 1982 at the creation of the headphones amp.The Power Soak is 

therefore "Tom Scholz's Power Soak" 

Though the Power Soak was not the first power attenuation device for guitar amps, it was the first to 

be 100% reliable, the first to respect the sound of the amp. Most of all, it was the first to include a 

volume control: the previous devices were only dummy-loads without setting. 

Objective and history 

� The old-school tube-amps can sound good, accidentally. As a matter of fact, someone with a brain 

will easily make the following statements: 

• These amps were created in a time where the bands had no mixer and no PA. They were thus 

way too loud for what we do today 

• The lack of gain of the preamps, and the lack of controls over the power-amp section, obliges 

the player to crank them up in the hope of getting a good sound 

• All in all, it's almost impossible to get a good sound of these old amps and to control the 

volume at the same time 

Tom Scholz has recorded the two first albums of Boston with these big, over-powered Marshall stacks, 

cranked up at 11. Since he's a clever man and knew that his ears are precious for a musician, he 

designed the Power Soak as a "Volume Control Device", as defined by the US patents 4,143,245, 


D256,798, 4,363,934 and D270,153. The Power-Soak not only attenuates the power of your amp: it 

allows a precise control over the global volume of your set-up. In other terms, tweak your sound first, 

then adjust your volume. 

� The personal prototypes used by Scholz from 1975 (?) till 1980 allowed the new-born company 

SR&D to issue its first product, the Power-Soak, in the end of 1980. The first commercial ads 

appeared in 1981, and were rather product oriented: the Power-Soak is a tool, not a toy, and it really 

solves a problem for the guitarist. 

An updated version of the original Power-Soak, known as "Model II", was issued in the end of 1981: it 

has an extra switch made to adapt the Power-Soak to the solid-state amps (though its primary target 

is the tube amps market). The resistors network was tweaked a little, for a more precise attenuation 

control (?). No audible sonic difference with Model I. 

Discontinued in 1982 when the Rockman headphones amp was created, the Power-Soak was reissued 

in 1992 as a PS-III model: the difference is in the jack positions (rear panel on the re-issue, 

front panel on the original). The solid-state switch has disappeared, and the manual says that the PS- 

3 can be used both with solid-state and tubes amps. The impedance selector has two positions only (4 

& 8 ohms), but 16 ohms amps can be used at the 8 ohms setting. 

� How many Power-Soaks were built? Around 10,000, if we refer to the number of eBay transactions 

per year. That's consistent with the serial number of a Power Soak I own, which has the serial number 

81-3391 (approximately 3500 per year). 

Features & Structure, Hook-up 

� The following pictures show the 3 types of Power Soak (Model II, Model I and Model III), front then 

rear view. That's fairly explicit... 

� The Power Soak must be first connected to the amp. Before doing that, one must set the Power- 

Soak to the proper impedance with the front panel switch (4, 8 or 16 ohms). 

Then one or two cabs (parallel mode) can be connected to the Power Soak outputs: once the Power- 

Soak is connected to the amp, this amp cannot be damaged, since its powerwill be anyway dissipated 


y the Power-Soak. Should someone turn his tube amp on before connecting a load to it, the accident 

will happen: the output transformer will probably blow out! 

The Power-Soak is not just a volume pot: it handles up to 100W power (equivalent to a regular light 

bulb), so using power-designed cables is absolutely necessary: using audio line signal level cables 

would certainly result in a shortage, blowing the amp out too. 

� Inside the Power-Soak, what do we have? A network of power resistors, housed in a grill-type 

enclosure designed to dissipate the heat. In the middle of the resistors network, a rotary selector that 

configures them for the desired attenuation: from -32dB to 0dB (full power setting). At -32dB, one can 

even connect the output of the Power-Soak to headphones or to a mixer: the signal level is now low 

enough for that. 

Usage, samples and limitations 

� The Power-Soak can be used in several situations: 

• Crank up an amp in the studio and turn down the volume until people can stand it... 

• Tweak the sound you want on stage, then adjust the volume to match the venue or the rest of 

the band (difficult for a guitarist, but you can do it!) 

• Bedroom playing: you can at least use your favorite tube amp at home with a decent sound! 

� I have put on line some samples recorded with a Power-Soak: search for them in the samples 

page. You will see (hear?) that the sound is good, knowing it was recorded in a flat with only an SM58 

in front of my Boogie, without specific care for the mike's placement. 

� Are there any limitations? Apart from the fact that the Power-Soak will not accept a 150W Triple 

Rectifier (it is "limited" to 100-120W), it's only fair to say that the less you attenuate, the better it 


sounds. It is not due to the Power-Soak itself: the guitar speakers are not linear and need a minimum 

amount of power to "breathe". If you send only a few watts into a guitar cab designed for 100W, the 

sound will be somehow flat and muddy. You can partially correct that with the tone controls of your 

amp, but let's say it: there's nothing like feeling the air moving with 100W in your ears, and you won't 

get the same sensations with 1W sent into a 4x12' cab. That's normal. Moreover, the human ear 

doesn't behave the same way at high SPL's or at low SPL's, making it impossible to compare bedroom 

level playing and stage level playing. 

This limitation is of course out of scope for normal attenuations: the Power-Soak is really respectful to 

the sound of your amp if you only need a few dB's attenuation. Remember that -3dB is equivalent to 

dividing the power by 2, and the Power-Soak can go down to -32dB (headphones level)! 

Collectibility and conclusion 

� With only less than 10,000 items sold worldwide, it can be quite hard to catch on eBay. Prices vary 

from $100 to $300, depending on the version, the condition and of course the current market demand. 

� It seems that no-one really cares about the model (I, II or III): as a matter of fact, I have made A/B 

comparisons (refer to the samples) between the three of them and though they have minor technical 

differences, cannot tell which is which in a blind test. 

The Power-Soak does it job and does it safely. It's an excellent tool, not to 

say mandatory tool, for any guitarist who loves the sound of his tube amp. 

Improved products have been issued since, with or without built-in cab sims 

(Allan Holdworth, Motherload, the well-known Palmer, THD Hotplate, 

Marshall's Power-Brake, etc...): none of them is as robust, versatile and 

simple as the mother of them all, the Power-Soak. 


Introduction 

THE HEADPHONES AMPS 

� If Boston is the band that has created the Adult Oriented Rock sound, the Rockman is the device 

that enabled creating the guitar sound of the eighties. From Sports by Huye Lewis - as soon as 1983 - 

to Satriani's Surfin' with the Alien via ZZ Top (Eliminator, Recycler, etc...) and Don Henley's "Building 

the perfect beast", the Rockman sound was omnipresent throughout the whole decade. 

This black box was a real revolution. Considered now as the ancestor of the modern digital 

multieffects, the Rockman was much more than a portable practice amp. 

� It was, more than anything else, the first amp simulator ever made available as a commercial 

product. 


� When Tom Scholz has created the Rockman, he had two different objectives in mind: 

1. Create a device that would allow him record Boston's music without the huge and 

cumbersome tube Marshall stacks: an amp simulator 

2. Create a commercial product for his young company, Scholz Research & Development: a 

headphones amp 

� The first SR&D product, the Power Soak, was a honourable success. Its nature (a professional tool) 

was not suitable for a wide distribution to the end-consumers. 

The Rockman was launched in 1982: it was an instant hit. In 1982, there was no homestudios, no 

DAW's, and playing DI through the band mixer was too exotic for a majority of guitarists. So the 

Rockman was completed by a fancy accessory: headphones! The name itself, Rockman, was based 

on Sony's Walkman ®, and a set of headphones was actually the most convenient way to provide 

quality stereo sound. 


Stereo was a fantastic and really new feature. Today, in 2008, we have forgotten what mono was: only 

old chaps like me remember the mono record players and tape recorders we used in the seventies! 

The younger generations don't even know that there was mono AM radio before the stereo FM they 

are used to... 

� Ahead of its time? No. The Rockman was right on time, and arrived exactly when the market 

needed such a tool. That's the key factor of all the success stories... 

Inside the Rockman 

� If you want to understand what a Rockman is and why it sounds so good, the first thing to do is to 

...forget the headphones! 

Think of the Rockman as a stereo amp simulator, designed to be connected directly into the 

soundcard of your PC, or in the mixer of your band. Once that said, let's take a look at the internal 

structure of a Rockman. 

� One can roughly identify two parts: a first mono section that corresponds to the amp simulator in 

itself. Then a stereo effects section, with a stereo chorus and a stereo reverb. 

All in all, you connect your guitar to the Rockman. The signal goes through: 

• A compressor 

• A distortion unit (or nothing in clean modes) 

• A cab sim 

That's the amp simulator. Then the stereo part, where the Rockman creates two different versions of 

the signal: 

• One channel is based on the dry, original sound, plus some reverb 

• The other channel goes through a short delay modulated by an LFO (thats the chorus effect) 

plus another reverb’d sound 

You have now two channels, left and right, with a huge spatial image due both to the stereo chorus 

and the stereo reverb. About the use of these two effects, you can read the section called "Rockman - 

the Concept" for an extensive analysis 


� The cab sim of the Rockman was, in 1982, a truly innovative concept: certainly the first circuit 

designed to reproduce the frequency response of a guitar speaker in such a small device. The 

concept was so new that SR&D didn't even think about calling it "cab sim". It was simply called 

"complex filter", and the following curve shows its frequency response. 

If this cab sim mimicks the frequency response of a guitar speaker, it cannot duplicate its dynamic 

response. And that was critical! 

� The main difference between a real amp and any amp simulator is that that the speaker has some 

physical, mechanical inertia that levels the tough peaks of a guitar signal. The attack of an electric 

guitar is way too strong to be pleasant to hear, and that's why we need these big speakers: they kinda 

compress these unpleasant attacks. 

Compression? Well, there is a compressor in the Rockman! And that's the real secret of Tom Scholz 

guitar sound, much more than EQ's, filters and saturation. 

The above diagram shows how the simple compression circuit of the Rockman limits the attack of the 

note, and attenuates the difference between the initial peak of the note and its decay. That's what a 


guitar speaker does with its mechanical inertia, and that what makes the Rockman sound realistic, 

combined with the cab sim. 

� A few words about the Rockman Distortion. If you are receptiveto the marketing speech of these 

common stompboxes manufacturers, I'm sure that you think the Rockman distortion had something 

special. 

Well, the Rockman distortion is the only classic part of the circuit! 

A distortion stage is nothing: compression, that alters the dynamics, and filters, that process the 

harmonics balance of a sound, are the critical factor. The Rockman Distortion in itself doesn't have 

any real importance, just like tubes or solid-state has a very limited impact on the final sound of a 

guitar amp: its design is from far more important. 

And here's a proof of this statement: though they sound alike, the Rockman and the X100 don't have 

the same distortion circuit... 

The following diagram describes the clipping (saturation) stages of both the Rockman and the X100. 

They are clearly different, and the corresponding waveforms are also different. The Rockman uses 

what is called a "soft-clipping circuit" with 4 diodes, while the X100 is based on a "hard-clipping circuit" 

with 2 LED's. 

Note: the terms "soft" or "hard" clipping refer to the position of the diodes in the circuit, not to their 

number. The Soloist has a 2 diodes soft-clipping circuit, for example. 

Does an X100 sound really different from a Rockman IIB ? No, of course: even if the clipping was 

made with a tube in one case, and an OpAmp only in the other one, the results would be very similar! 

The compressor before the clipping stage, along with the cab sim after the clipping stage, are the two 

elements that really make the sound. 


� The compressor and the cab sim, joining their functions, have the role that a speaker has in a guitar 

amp. 

The message can be summarized as follows. 

When you listen to someone playing electric guitar, what you get is: 

1 - The player himself 

2 - The cab 

3 - The electronics 

The electronic part of an amp has a limited impact on the sound. That's the reason why the Rockman 

allowed easily to replace these huge Marshall stacks: their electronics had a very little influence on 

what was recorded, and Tom Scholz managed to capture the response of a recorded guitar cab inside 

his little black box! 

Evolutions & Features 

� The original Rockman (1982) was followed by five similar guitar products: 

Type Birth Clipping Sounds Chorus Reverb 

Rockman 1982 Soft CLN2/CLN/EDGE/DIST Yes Yes 

Ultralight 1983 Soft CLN2/CLN/EDGE/DIST Yes No 

X100 1984 Hard CLN2/CLN/EDGE/DIST Yes Yes 

Soloist 1984 Soft CLN/EDGE/DIST Yes No 

Guitar Ace 1990 Soft CLN/EDGE/DIST No No 

Metal Ace 1994 Soft CLN/EDGE/DIST No No 

• Note 1: the Ultralight was strictly a Rockman IIB without reverb. 

• Note 2: the Soloist was a real new product with its own design: actually, a simplified Rockman 

circuit. 

• Note 3: the Guitar Ace has no effects. It is basically the amp simulation part of a Rockman. 

• Note 4: the Metal Ace is a Guitar Ace with more gain and a different voicing. 

� The Rockman & X100 line was in constant evolution. As a matter of fact, there were 7 revisions 

(from REV1 to REV7) for the Rockman, called Rockman, Rockman II and Rockman IIB, and 3 

revisions for the X100 (from REV8 to REV10). There are minor external changes that can help 

identifying the actual REV# of a Rockman, but the only reliable solution is to read it on the PCB, inside 

the enclosure. 

• A Rockman I can be a REV1 or a REV2 

• A Rockman II can be a REV3 or a REV4 

• A Rockman IIB can be a REV5, 6 or 7 

• The REV8 is stamped Rockman on the front, and X100 on the back 

• An X100 without power supply TRS mini-jack can be a REV9 or a REV10 

• An X100 with a power supply TRS mini-jack is a REV10 


� Apart from the soft versus hard clipping difference described above, the Rockman differed from the 

X100 by an additional switch, actionned mechanically by a folded metal square: Tom Scholz has 

always been fond of these mechanical tricks! 

The square pushes the additional switch when the Rockman is in EDGE or DIST mode. In the X100, 

this trick has disappeared: its purpose was to shift a filter that was necessary in the Rockman. 


The square was often lost on the old Rockman's, causing an unpleasant sound in distortion modes. 

Bass headphones amps 

� The guitar headphones amps range was completed by two bass products: 

• The Bass Rockman, in 1984 

• The Bass Ace, issued with the Guitar Ace in 1990 

The two units are totally different: while the Bass Ace is an economic mono product with minimum 

features, the Bass Rockman is a genuine stereo professional product with amazing features for its 

size: 

• Built-in DBX compressor 

• Stereo chorus, specially voiced for the bass 

• Several filters providing various EQ settings 

• Distortion stage 

• Anti-click filter for people playing bass with a pick 

� In other terms, the Bass Ace cannot really be used without post-processing, while the Bass 

Rockman can provide a complete range of finished stereo sounds, directly useable for a professional 

production. 


� The users themselves have certainly been really creative with the Rockman, and it's impossible to 

make an exhaustive list of the configurations that people have used since 1982. Basically, in 2008, 

here are the most common usages of a Rockman headphones amp. 


• Practice amp 

This is the immediate function of the Rockman: pick up a headphones set, connect your guitar to the 

Rockman, and enjoy this huge stereo sound! You also can connect an mp3 player and jam along with 

your favorite songs, or work with a backtrack. 

• Homestudio 

That's where the Rockman becomes really interesting. In 1982, homestudios were the privilege of 

some happy fews. We are in 2008, and if you read these lines, you have a PC and probably a 

soundcard - hence a homestudio. 

The first function of the Rockman is the amp simulation, designed for DI. Connect your Rockman into 

the stereo input of your soundcard, and you will really appreciate its ease of use and its sound quality. 

• Rehearsal 

Tired of hauling your heavy amp and effects rack between home and the rehearsal room? Take your 

Rockman and walk! Thousands of people have done it before you, for rehearsal, studio sessions or 

even stage use. In 2008, I wouldn't recommend using a Rockman on stage, because of its limited 

switching features, and a professional studio has of course many ways to achieve the same results. 

But in everyday's life, the magic little black box still does its job, and does it well! 

� How does a Rockman sound? That's, after all, an important question! If you have really never heard 

one, you will find plenty of samples on this dedicated page. The best being of course to buy one and 

try it by yourself... 

� What are the limitations of the Rockman? As stated above, the switching system is really poor, and 

makes it difficult to envisage a constant usage on stage: real time sound change is almost impossible. 

The Rockman is based on presets (the 4 basic sounds) and the chorus and reverb have fixed settings: 

don't expect creating your own sound with a Rockman! 

The only real drawback of the Rockman is the fact that you can turn off the chorus or the reverb, but 

not the both of them at the same time. This is weird, but that's the way it is... In case you want a non 

processed Rockman sound, you have to pick up the rare Ultralight, or turn towards the economic 

Soloist and Ace. 


� The total quantity of Headphones amps produced by SR&D is certainly above 40000: they are not 

rare at all, and are now cheap compared to what they originally costed in the eighties. 

� Depending on your budget, you can pick up a Guitar Ace for $50, or go above $100, sometimes 

$150 for an X100 in good shape. A complete model with its original box and accessories will of course 

call for more. 

Due to the continuous improvements brought by SR&D, it is recommended to look for the latest 

model, i.e. a REV10 X100, recognizable by its side power-supply mini-jack. Remember that the early 

Rockman models require a Rockadaptor to be used with an external wall-wart! The Ultralight is very 

rare, and is praised for... its lack of reverb! It's actually the only way to have the straight sound of a 

Rockman without chorus nor reverb added. The Soloist is often underated: while its features are 

similar to those of an Ultralight, it is usually much cheaper. 

The homestudio trend makes the Rockman headphones amps more 

attractive today than what they were in the nineties. They are a wonderful DI 

box providing directly a fully processed guitar sound: as a matter of fact, we 

are back today to the original mission of the Rockman, the headphones 

function being a secundary feature. 


ROCKMOUNT, ROCKMAX AND ROCKBOX 

� The Rockman was officially presented as a headphones amp, a sort of practice device designed for 

home use. Yet, it was also the first commercial amp simulator designed for DI, and that's what made 

its success. The problem was to conciliate its fantastic musical possibilities and its poor mechanical 

layout: a lot of people have hacked the circuits to allow more switching and easier connexions, while 

three commercial add-ons were issued in order to convert the headphone amps into something that 

would fit the musicians requirements on stage or in the studio. 

These were: 

• The Rockmount, that converts the Rockman into a 19' rack unit 

• SR&D's Rockmax, a modification that added footswitching features to the Rockman 

• The Rockbox, that converted the Rockman into a regular pedalboard with full footswitching 

capacities 

The Rockmount 

� The Rockmount was manufactured by Four Designs Company. Its purpose is to host a Rockman 

headphone amp (Rockman, X100, Soloist or Bass Rockman) in a 19' rack format. 

The Rockman must be inserted into a specific case, batteries cover out, and a Rockadaptor bolt in the 

rack provides the required supply voltage to the unit. Two jacks are connected to the guitar input and 

one of the headphones outputs. 


� The features of the Rockmount are fairly limited: 

• Guitar input on the front panel 

• Global bypass footswitch jack on the rear panel 

• Dry/Processed balance pot 

• Guitar level output jacks on the front panel 

• Line level output RCA outputs on the rear panel 

� The Rockmount provides no control over the Rockman, and its only real interesting feature is the 

dry/wet balance pot. Mainly designed for a studio usage, the Rockmount did not transform the 

Rockman into a stage unit. 

The Rockmount had one quality: the Rockman itself was not modified at all, for the best and the worst. 


The Rockmax 

� While the Rockmount was a third-party product, the Rockmax was a genuine modification proposed 

by SR&D. 

� The Rockman received an additional PCB with some J-FET switches, and two jacks bolted in the 

bottom of the enclosure. 

� Connected to these two jacks came a (big) pedalboard that allowed remote control over: 

• The channel: DIST to CLN, CLN2 or EDGE, depending on the position of the slider switch of 

the Rockman 

• The chorus (On-Off) 

• The volume (High or Low) 


The global shape of the Rockman didn't change, and it was therefore far from becoming a real stage 

unit, but at least, the Rockman could be used on stage without having to go through the tiny slider 

switches! 

� The Rockmax was an excellent compromise, that left the Rockman almost unchanged, while the 

additional footswitches provided enough possibilities to use the Rockman live on stage. 

The Rockbox 

� The Rockbox was another third-party add-on for the Rockman, made by Electronics Specialty 

Services. From far the most complex, it converts basically the Rockman into a real multieffects 

pedalboard. 


� The Rockman was modified with 1) an additional PCB with a series of J-FET switches, 2) a 25 pins 

connnector that links the Rockman to the control electronics of the footswitches. Once closed, the 

Rockbox was a big and handy stompbox, with 4 footswitches for the 4 channels and two switches for 

the Chorus and the Reverb. 

� The Rockbox is clearly the most interesting modification for a Rockman, and transforms it into a 

genuine stage unit (that can of course also be used in a studio). The chorus and the reverb were at 

last independant and could be turned off and on with their own footswitch. 

The addition of the 25 pins connector was unfortunately necessary, but it was of course a deep 

modification of the unit (though the Rockman can still be used as a standalone device). 


THE ROCKMODULES 

� The Rockman has created the name, 

the sound and the notoriety of the brand. 

The Rockmodules, introduced in 1986, 

rapidly became the core of SR&D's offer, 

and more than 20 years later, are still 

what the collectors look for. 

� The Rockmodules were all designed 

to be high-end analog devices, and it's 

still what they are today: the 

manufacturers having targeted their 

efforts in the digital domain, the overall 

quality of the Rockman half-racks has 

been sometimes equaled, but no 

manufacturer can claim he has a 

complete range of analog guitar gear at 

this level of quality. 

� There are roughly three categories of 

Rockmodules: 

• The amp simulators (Sustainor 

and Distortion Generator) 

• The sound processors (EQ, 

Compressor, Smart Gate, 

Chorus, Echo) 

• The control devices (Midi 

Octopus and Dual Remote Loop) 

It is difficult to compare the Sustainor and its derivation, the Distortion Generator, with today's gear: 

they are defined more by their sound than by their qualities, and one may like this sound or not. 

The Midi Octopus was copied several times by other manufacturers (though a midiswitcher is not 

something that you can find easily), and after all, it is not an audio device. 

But the sound processing modules are all references in their category, even today. 

That's what makes the Rockmodules unique: the Rockman Stereo Chorus is the best stereo chorus, 

the Instrument EQ has no competitor, the Guitar Compressor is unequaled, etc... 

� Let's review all these magic boxes one by one, in detail. Then all you'll have to do is to try to buy 

them and make your own opinion! 


Introduction 

SUSTAINOR 

� The Sustainor is the heart of every Rockman rig. It is certainly the most complex and the most 

charismatic of the Rockmodules: its development required several years from a complete team of 

engineers, probably working separately on sections of the Sustainor. 

Though its sound signature is immediately recognizable, the possibilities and versatility of the 

Rockman Sustainor are almost endless, still over twenty years later. 

� Certainly the first high-end analog amp simulator ever built, the Sustainor is, still today, an 

outstanding device, far above the classical preamp image that some people have of it. 


� The basis of the Rockman Sustainor is the amp simulation of the Rockman headphones amps. If 

one considers that the Rockman and the X100 are semi-professional devices, then the Sustainor 

stands as the professional extrapolation: while the headphone amps are based on four preset sounds, 

the Sustainor was extended by several complex, smart and useful inventions. 


� The Rockman headphone amp was created by Tom Scholz and issued in 1982. SR&D improved it 

continuously between 1982 and 1986, without significant changes: only minor circuit tweakings. 

In the meantime, Tom Scholz had imagined the improvements that would give birth to the Sustainor: 

• Adjustable gain stages, volume controls and filters. 

• A noise reduction circuit: the Smart Gate 

• A truly amazing feature: the Autoclean 

• A 4x12' cab simulation: the Phase Notcher 

� When did the studies for the Sustainor begin? Probably right after the issue of the Rockman: 4 

years is not much when the deal is to stuff 1kg of components in the volume of a pocket book! All in 

all, the Rockman Sustainor was issued as a commercial product in January 1986, along with the 

Rockman Chorus/Delay. 

The Sustainor, like all the Rockman products, was continously improved. The first commercial items 

correspond to the REV03, knowing the last commercial release, in 1989, was REV09. 

The first models had this blue logo that make us call them "Blue face", and the rear plate was stamped 

"100" (as a matter of fact, all the Rockmodules are stamped 100 and it's more an enclosure type than 

anything else). SR&D sold almost 9000 Sustainors in 1986. In February or March 1987 (circa S/N 

10000), the rear plate was stamped 100A, and the blue logo was still here. These 100A Sustainors 

have nothing special: they are just the last Blue-Face Sustainors, a sort of transition model before the 

change of logo. 

In October 1987, the logo on the frontplates of the Rockmodules (i.e. the Sustainor, the Chorus/Delay 

and the Instrument EQ) received a white logo instead of the original blue one. The Chorus/Delay was 

actually discontinued, and the existence of white-faced C/D's or blue-faceed EQ's as commercial 

products is not proved. 

The change of logo was accompanied, for the Sustainor, by a change of rear plate: it was now 

stamped 200 instead of 100. The front plate was slightly modified, and all these changes make us 

speak about the Sustainor 200, though the 200 is just a continuous improvement of the 100, not a 

different product. 

� All in all: 

• A total of over 21000 Sustainors were made and sold between 1986 and 1992 

• The early Sustainors are called 100 or "blue face" and can be identified by their blue logo 

• The later Sustainors are called 200 or "white face" and can be identified by their white logo 

• The best Sustainors are the younger ones, and the manufacturing date, along with the Serial 

Number, is the key to choose one 


Inside the Module 

� The Sustainor is complex. Very complex. While the amp simulation circuit of the original Rockman 

took only 6 OpAmps controled by only one mechanical switch, the Sustainor is made of 28 Opamps 

with a complete network of mechanical and J-FET switches. 

� Let's have a look the structure of a Sustainor to see what are all these OpAmps and Switches are 

made for. We can compare it to the structure of the X100's amp sim for an easier understanding: 


� The first addition is the Smart Gate, placed right after the compressor, i.e. right before the distortion 

stage. As a matter of fact, noise doesn't come from distortion itself: the distortion overamplifies 

evrything, and the most discrete breathe can become a real wind sound! The Smart Gate is here to 

suppress all the breathe noise that the compressor can generate. 

What does the Smart Gate do? A classical noise-gate does two things: 

1. Compare the signal level and a threshold 

2. Cut the sound if the signal is below this threshold 

Of course, a noise gate cuts the noise, but it cuts the signal too! The Smart Gate operates differently, 

and does two things: 

1. Follow the signal level instead of comparing it to a threshold 

2. Opens or closes a low-pass filter proportionnaly to the signal level 

Closing the filter cuts-off the high frequencies where noise is present, an never, never cuts off the 

main part of the note. This principle is derived from a more general principle called "adapted filter", a 

math-based noise-reduction approach that usually requires very complex circuits (such as the circuit of 

Rocktron's Hush). Scholz just did the same thing with classic components and a lot of time spent 

tweaking his circuit... 

� The next significant addition is the circuit called Autoclean. We all know that turning down the 

volume pot of the guitar reduces the gain of the distortion: to a certain extent, we can go down from 

plain distortion to light overdriven sounds. To a certain extent only: the balance between the treble and 

the bass frequencies is messed up, and we lose a lot of dynamics. Moreover, it is virtually impossible 

to go as low as a clean sound with this technique. 

Well, all in all, the Autoclean circuit allows doing all that: total control over the saturation without signal 

loss, without dynamics loss, from the guitar volume pot! It is even possible to reduce the gain down to 

the clean sounds range. 

Though the basis of the Autoclean circuit doesn't look complex, it was actually very tricky to design, 

and as a matter of fact, only the younger Sustainors have an Autoclean that really works great. 

� Then the Phase Notcher. The Rockman cab sim (see the Headphones Amps review for details) 

simulates the behavior of a plain single-speaker cab. Some guitarists are used to the weird response 

of a multi-speakers cab: this technique was used in the sixties when the speakers had very low 


sensitivities, cause it was the only way to make an amp sound loud. It became 100% useless ver the 

years, but the habit is still here: some people love the feeling of a 4x12' cab, as if they were playing in 

the Shea Stadium everyday. Well, multi-speakers cabs have a sonic drawback: there are interferences 

between the speakers that cancel some frequencies... 

The objective of the Phase Notcher is to simulate this default: it produces a nasal sound, that you may 

like or not. The following curve depicts the frequency response of the Phase Notcher: 

� The Sustainor has another smart trick that can be really helpful: the rhythm volume footswitch. This 

turns down the global output volume a little, and at the same time scoops the mid frequencies to leave 

room to the lead instruments or vocals within a mix. Simple and efficient! 

� Last but not the least: the Sustainor has a special loop designed to host a pre-distortion equalizer. 

Placing an EQ before the distortion stage and another EQ after the Sustainor is the key to all the 

possible sound variations, from mellow to harsh and from classic rock to modern sounds (refer to the 

Rockman Concept section for details). 


� The endless parameters combinations of the Sustainor make it an extremely complete and versatile 

tool. The samples and tracks posted on the dedicated page show how far one can go with Rockman 

gear: listen for example to the cover of "Shine on you crazy Diamond" to see (hear?) that a Sustainor 

is much more than a Boston-in-a-box tool. 

The first contact may be a little surprising: if you play alone during the first test, you will probably find 

the sound a little nasal! That's perfectly normal, if you consider that the Sustainor was designed to play 

guitar within a band, i.e. with other instruments. A guitar is always mixed with an emphasis on the mid 

frequencies (except in this weird death-metal-trash-core teenagers' stuff!), and the Sustainor pre- 


processes the sound in this spirit. In a second approach, you can try to play along with any classic 

rock record (Lynyrd Skynyrd, ZZ Top, etc...) and you will hear the magic happen! 

� Any limitations? Well, it is highly recommended to use the Sustainor with a pair of Rockman EQ's if 

you want to dial your own sounds. One could also regret that only 2 modes out of 4 can be controlled 

by the footswitches: a modification is necessary to access the 4 of them. 

Apart from this secondary issues, the Sustainor is what it was made for: a professional analog amp 

sim for the most demanding musicians. 


� Buying only a Sustainor, without the rest of a Rockman rig, is of course possible. Yet, one can very 

rapidly see that it's a sort of nonsense: the Sustainor is the heart of a Rockman rig, so the question of 

its collectibility as a stand-alone unit is pointless. Either you need one, either you don't. 

Moreover, the Sustainor is not rare at all: with over 21.000 items on the market, there are always 

several Sustainors for sale on eBay, with prices ranging from $100 to over $400. 

� The question is more "which Sustainor should I buy", knowing the 4 possible choices are: 

• A Sustainor 100: the cheapest and the oldest 

• A Sustainor 100A: slightly better, but not much 

• A regular Sustainor 200, still affordable 

• A "young" Double-IC Sustainor 200, quite expensive for what it is 

Buying a Double-IC because of this Lead-Leveller feature only is fairly stupid: as a matter of fact, 

nobody can tell the difference with or without Lead-Leveller. But there's another factor that must be 

taken into account: take two Sustainors and make an A/B comparison, and you will always hear a 

difference. So, all in all, since you cannot try a Sustainor before you buy it, the only rule to follow is 

"the younger the better": hence the Double-IC domination on the second-hand market. 

Buy a 100 if funds are an issue, buy a 200 if you want less noise and a better Autoclean. Buy a 

Double-IC if you need a garantee to have the youngest possible engineer revision, hence the best 

Autoclean. 

� And most of all, remember that a Sustainor with its original electrolytic capacitors needs a thorough 

refurb before sounding the way it deserves! The Rockmodules are 20 years old now, and their caps 

are at the end of their life. 

The Sustainor is, still today, an excellent amp simulator. Truly mandatory for 

any Rockman fan, it can also be the first module to buy for a newcomer. 

Worth buying anyway because of its endless possibilities. 


Introduction 

INSTRUMENT EQ 

� In a first approach, an equalizer is only an equalizer. Something simple that all the manufacturers 

should be able to design correctly. 

But if you ask someone like Tom Scholz if the common commercial devices fit his requirements, and 

the answer is less obvious. 

� The Rockman Instrument EQ is just different and better than what's available on the market. Let's 

see what makes its qualities and differences. 


"[...]a couple of years ago we designed a graphic equalizer. Now, how crazy is that? 

There are dozens of them on the market, but there was not a single one that could be used with a 

guitar level signal, was footswitcheable, had a decent signal-to-noise ratio, and could give better than 

an octave resolution. 

We tried to modify existing units, but finally gave up and designed the stupid thing so we would have 

what we needed." 

(Tom Scholz in Guitar World, Feb. 90) 


� What were these modified EQ's used by Boston, before the Rockman EQ was born? On this picture 

from the 1987 tour, we can see that Boston used Boss 10 bands EQ's: these were the modified units. 

� The first Rockman EQ prototypes were certainly reproductions of these modified 10 band EQ's, 

housed in a Rockmodule enclosure to match the existing Sustainor and Chorus/Delay. The following 

picture, grabbed from a 1987 guitar magazine, shows this un-issued 10 bands Rockman EQ, the draft 

of the 12 bands model we all know: 

� Bob Cedro, now MXR's chief-engineer, was in charge of the development of this 12 bands 

Rockman Instrument EQ. The first models, made in 1987 had the same blue logo as the Sustainor 

100 and the Chorus/delay, as on this ad published in December 1987: 


Then the white face series was issued, with the Stereo Echo and the Stereo Chorus: the Instrument 

EQ was finally a white-face too, and these blue-face models must be extremely rare now. 


� The first thing that a tech will see inside the Instrument EQ is... no 4053/4066 chips! These J-FET 

IC's are everywhere in the other modules, and were not used in the EQ. As a matter of fact, SR&D 

designed it for the best signal-to-noise ratio, and selected a +/-12V power supply - instead of +/-8V - 

that prevented from using the integrated switches (the bypass circuit is therefore based on discrete J- 

FET's). 

The higher the power-supply voltage is, the stronger the signal can be, and the better is the S/N ratio: 

with a total amplitude of 24V, the immediate improvement is 4dB compared to a 9V powered 

stompbox. The Rockman EQ can thus be used both with guitar level signals, as required by Tom 

Scholz, and strong line-level signals (up to 14dB): there is a switch on the Rockman EQ that selects 

the operating signal level (Normal: line level or Hot: instrument level). 

� Back to the features of the unit. The real difference between a classical EQ and the Rockman 

Instrument EQ is the presence of 3 additional bands in the mid-frequencies: 

• 62,5 - 125 - 250 - 500 - 1000 - 2000 - 4000 - 8000 and 16000 Hz classical octave bands 

• 700 - 1400 and 3000 Hz additional mid-frequency bands 

The range of each band is +/-12dB: all in all, the Instrument EQ is extremely precise and efficient, and 

allows the best sound sculpture for the most demanding musicians. 

This is not instrument gear any longer: the Instrument EQ is a genuine studio-quality device. 


Usage and limitations 

� The Rockman EQ is truly mandatory for anyone who really wants to create and tweak his own 

sounds. When one starts building a Rockman rig with a Sustainor, it becomes rapidly obvious that two 

EQ's are necessary: one placed in the loop as a pre-distortion EQ, the second one being placed after 

the Sustainor. 

The possibilities provided by a pair of EQ's are both subtle and endless. Changing a few dB's on a 

frequency band can alter significantly the sound and the position of the guitar in a mix, and using 

radical settings can also deliver specific sounds: fuzzy or metallish, fixed-wah effects, etc... 

� As a matter of fact, EQ'ing can become very complex, and can turn into a real nightmare. Finding 

the perfect sound is impossible, and the situation was perfectly summarized by UseHerName on the 

boards of Gonnahitcharide.com: 

You are suffering from a condition know as O.A.D. (Obsessive Adjustment Disorder). The good news 

is that there is help. You are not alone. First you must recognize that you do have a problem. Then 

you must have a desire to change your behavior. I have devised a three step program to help others 

like you on the road to recovery. 

Disclaimer: Author assumes no responsibility for damage to equipment resulting from users adherence 

to the recovery program here by known as R.O.A.D.I.E. (Reversing Obsessive Adjustment Disorder Is 

Easy). 

Step one: 

Set all EQ sliders flat. Pick up your guitar. Play. DO NOT TOUCH THE EQ FOR 24 HOURS. 

Do not go on to step two until you successfully complete step one. YOU CAN DO IT! 

Step two: 

Find the sliders on both ends of the unit that only dogs can hear. Leave them flat or cut them as you 

wish. If you have a dog, allow the dog to set those sliders on your behalf. Pick up your guitar. Play. DO 

NOT TOUCH THE EQ FOR 24 HOURS. 

Do not go on to step three until you have successfully completed steps one and two. 

Step three: 

You must now accept the fact that no matter how many sliders are on your EQ, there are only a few 

that matter most for guitar. It is generally accepted that those are roughly 500 to 2k. You may now 

adjust those sliders to your liking. You may re-adjust those and only those as many times as you wish 

for a period of 24 hours. After the 24 hour adjustment period has expired you must then permanently 

disable those controls. Break off the sliders with a pair of pliers. If you don't have pliers ask your dog to 

bite them off for you. If you don't have a dog a wife will do nicely. 

Pick up your guitar. Play. Don't look back..... 


Introduction 

CHORUS/DELAY 

� There are tenth of chorus effects and dozens of delays on the market. But there is no other device 

like the Rockman Stereo Chorus/Delay. 

Its sonic quality is outstanding, and the features of this half-rack makes it truly different from any other 

device. One may think that the unit is a classic chorus and delay, packed inside the same enclosure. 

� It is actually a chorus or a delay: it was done on purpose, thus making the Rockman Chorus/Delay 

a complete space-maker, rather than one more effect machine. 


� If you have read in details the section called “Rockman - The concept”, you know what a chorus is 

made for, and you also know the role of a slight delay during a recording process. 

Both of them are here to switch from the dry mono sound provided by a guitar to a stereo sound, a 

sound with air and depth. 

That's the objective of the Chorus/Delay: it can provide the classic doubling effect of a chorus, that 

simulates the presence of two guitars playing together, but as a delay, it can also give dynamics and 

depth by using very short echo sounds (within the 200ms range). 

� The Chorus/Delay was issued with the Sustainor 100, in January 1986. This second blue-face 

Rockmodule was produced until the last quarter of 1987, and was replaced by two units: the Rockman 

Stereo Chorus and the Rockman Stereo Echo. These new items didn't make the Chorus/delay 

obsolete - just different. 



� The heart of the Chorus/Delay is the MN3005 BBD chip. A BBD is the basis component of all the 

analog chorus effects (25ms delays with an excellent Signal to Noise ratio). It can be pushed up to 

200ms delays, at the price of a S/N degradation: 75dB only at the longest delay setting. 

� In order to improve this poor S/N ratio, SR&D has included in the Chorus/Delay a noise-reduction 

circuit, based on the same principle as the Dolby System: a "compandor". 

A compandor is a dual circuit composed of 1) a compressor before the source of noise (the BBD in our 

case), 2) an expandor after the source of noise. 


The expandor increases the level difference between the sound signal level and the noise level. The 

signal-to-noise ratio is highly improved, but the dynamics of the sound signal is of course altered. 

That's why there is a compressor placed before the BBD: the combined action of the compressor and 

the expandor is neutral for the sound signal, while the noise level is highly reduced. 

This compandor system is too expansive for the common chorus and delay stompboxes, and are 

found only in costly units. It is clearly one of the qualities of the Chorus/Delay, that makes the 

difference with its competitors. 

� Back to what the Rockman Stereo Chorus/Delay does: Stereo, Chorus and Delay... 

The chorus effect is achieved by sending the original sound through a 20 to 40ms delay, slightly 

modulated (e.g. 20 to 25ms) then mixing that with the original sound. The result sounds like two 

guitars playing together. 

In order to have a stereo image, one must separate the original signal and the delayed signal, send 

one of them to the left channel, the other one to the right channel. 

That's the widest stereo image you can have, and that's what the common stompbox chorus do not: 

these pedals are designed to be mono-compatible, so their main output delivers the sum [original + 

delayed] signal. 

When the manufacturer wants to build a so-called stereo image, the other output is only the difference 

[original - delayed] signal. This is not full stereo, and that's the other significant difference between the 

Rockman Chorus and the other devices. 

All the Rockman Stereo units (Chorus/Delay, Stereo Chorus and Stereo Echo) have a specific output 

stereo mixer, that allows tweaking the wideness of the stereo image, from mono to wide stereo. 

� SR&D added another feature in the Chorus/Delay: the delay of the BBD, usually 20 or 25ms in a 

chorus, can be doubled and be set at 40ms. This is the limit between doubling (when the ear cannot 

separate the two sounds) and a delay (the human ear clearly hears two disctinct sounds). This Long- 

Chorus mode provides a deeper effect than the normal mode. 


� As for the delay section of the Chorus/Delay, we have here a conventional delay/feedback/level set 

of sliders. The delay time, as said above, can go up to 200ms: coupled with the output stereo mixer, 

this allows building all sort of reverbish or slap-back stereo sounds. 


� The main usage of the Stereo Chorus/Delay is of course the classic Rockman chorus sound (for a 

guitar, a keyboard or even connected to a mixer). It can also be used for slap-back echoes and 

reverbish sounds. 

� The only limitation of the Chorus/Delay is the lack of footswitches: it has only a bypass, a 

chorus/delay selector and an output mix selector. The other features (long chorus, long delay) are not 

remote controlled. 


The Chorus/Delay is fairly easy to find (6800 units). It is an excellent value 

for someone who wants this Rockman Chorus sound, and its delay functions 

compensate for the simplicity of its chorus section. 


Introduction 

STEREO CHORUS 

� The Rockman Stereo Chorus was introduced in 1987, when the older Chorus/Delay was 

discontinued. Based on the same circuit, it has the same qualities, plus some improvements that make 

it a genuine reference. 


� The Chorus/Delay was a combined unit. Like in all the multi-effects, some features were limited: 

some footswiches would have been welcome, but the rear panel was simply too small for that... 

� The new Stereo Chorus was therefore entirely dedicated to the chorus function, and all the switches 

were now remote-controled. The Stereo Chorus has a total of four footswitches: 

• Bypass 

• Long-Chorus 

• Sweep Stop 

• Alt-Mix 

The possibilities are of course huge, and the technical quality of the unit - already great for the 

Chorus/Delay - were improved again. 



� The Stereo Chorus has the same structure and circuits as the Chorus/Delay. This includes of 

course the noise reduction compandor. 

The key difference is the BBD's: the Chorus/Delay has one MN3005 chip (up to 200ms), while the 

Stereo Chorus is based on two MN3007 (up to 50ms each). The choice of two BBD's was made to 

allow a silent switching between the Normal (20ms) and Long-Chorus (40ms) chorus modes. 

� The Stereo Chorus, as said before, has two footswitches that the Chorus/Delay doesn't have. 

The Sweep Stop footswitch de-connects the LFO modulation from the BBD, and the Stereo Chorus 

can thus act as a fixed-delay stereo doubler (20ms or 40ms). This feature can be used to enhance the 

sound of an instrument in a mix (if you listen to such a sound individually, it may sound weird). 

The Long-Chorus already existed in the Chorus/Delay: it provides a deeper chorus effect. In the older 

unit, switching was made by a push-button on the front plate, and since there was only one BBD, it 

was done by a clock change that caused a sort of brief woosh sound, just like what you have when 

you turn the delay pot of a delay unit. In the Stereo Chorus, there are two BBD's, and the second one 

is activated with this additional footswitch, without that woosh. 


� The Stereo Chorus is almost perfect. It is an outstanding unit, certainly the most professional 

chorus effect on the market. If one really wants to find a limitation, let's say that it has no depth control: 

the Stereo Chorus was designed to provide a chorus enhancing effect, not to dismorph the sound like 

any stompbox. 


� The Rockman Stereo Chorus is not rare. Almost 7000 units were made, and its market price is 

really attractive for what it is. 

A reference tool, with almost perfect qualities: the Rockman Stereo Chorus is 

something you will love and keep in your rig, simply because no other chorus 

can sound the same. 


Introduction 

STEREO ECHO 

� The Rockman Stereo Echo is often considered as the Holy Grail of the analog delays. 

Well, it's only fair! 

There aren't many quality analog delays on the market, especially since this technology was replaced 

by the cheaper digital technology. 

� The Rockman Stereo Echo not only uses state-of-the-art analog circuits, its functional design was, 

like every other Rockman unit, performed by a musician for musicians. 

And that makes a huge difference. 


� The Stereo Echo was issued along with the Stereo Chorus when the Chorus/Delay was 

discontinued in 1987. 

And the delay section of the older C/D looks really simple compared to the highly improved Stereo 

Echo! While the Chorus/Delay was limited to doubling, slap-back and reverb-like short echoes, the 

Stereo Echo can deliver these huge walls of sounds that a tape echo can give. 

As a matter of fact, the filters of the Stereo Echo were designed for this warm, tape-like sound - 

nothing like the cold feeling of a digital unit. 


� The stereo effect of the SE is unique: the left channel delay is always equal to 3/5 of the right 

channel delay. This ratio was introduced to avoid taps overlapping: the echoes interleave from left to 

right and right to left without crossing path. 

This special feature allows the Stereo Echo sounding a little like a reverb - something that no classic 

delay can do. 


� Just like the Stereo Chorus and the Chorus/Delay, the Rockman Stereo Echo includes the 

compandor noise reduction circuit. This is one of the key features that make it sound clean, when the 

common analog delays are fairly noisy at long delay settings. 

There are four BBD chips inside the Stereo Echo, which are connected in series. The Left Channel - 

short delay - is picked up after the third chip, and the last chip provides an extra delay for the Right 

Channel. 


� The following chart is a simplified diagram of the Rockman Stereo Echo's structure. The right input 

channel is left untouched, and is mixed towards two outputs with the original left channel, the short 

delay and the long delay to achieve the desired stereo image. 

� The output mixer, apart from the same mono-to-wide switches as in the Chorus units, has a three 

positions switch to select three patterns: 

• Input stereo signal mixed to mono, short delay left, long delay right 

• Input stereo signal unchanged, short delay left, long delay right 

• Input signal left, delayed signal right 


� The Rockman Stereo Echo has very rich features, and a guitarist will certainly never find the limits 

of the unit: from discrete slap-backs to huge walls of sound, the Stereo Echo will meet his 

requirements. 


� The Stereo Echo is becoming difficult to catch at a decent price. It was produced in the same 

quantity as the Stereo Chorus - approximately 6700 units - but people who can buy one do keep it, 

and a lot of collectors own several of them. 

The Stereo Echo doesn't steal its reputation: it is an outstanding unit, that 

really has no competitor on the market - unless you prefer digital to analog 

gear. 


Introduction 

GUITAR COMPRESSOR 

� The name itself says it all: we are speaking about a Guitar Compressor, i.e. a compressor that was 

designed especially for the guitar. In other terms, the other compressors that you may encounter were 

never designed for this special usage! As a matter of fact, no other compressor takes into account the 

very specific dynamics of a guitar note: they compress, full point, and you have to like the result or not. 

� What are the compressors that you can buy ? Either cheap circuits stuffed into a pedal format, 

either costly studio units that are really cumbersome and costly solutions for what a guitarist needs. 

The quest is over: the Rockman Guitar Compressor is unique, and really meets a guitarist's 

requirements, without concession. 


� Tom Scholz has spent a lot of time on the compression topic. As explained in Rockman - The 

concept, compression is a key feature of the Rockman sound, that allows getting natural sounding 

clean sounds and distortions with a very long sustain. 

Every Rockman amp simulator has a built-in input compressor, from the first Rockman headphone 

amp, in 1982, to the AGP and the UDG, in 1993: it was only natural to expend the basic circuit present 

in every item into a dedicated unit: that's how the Guitar Compressor was created. 

� The funny fact is that, since there is already a compressor in every Rockman item, the Rockman 

Guitar Compressor is perfectly useless if you use Rockman gear! As a matter of fact, the Guitar 

Compressor was designed as an add-on for people who play with a classic guitar amp - but want this 

Rockman compression sound. 



� The Rockman compression circuit being a key part of the Rockman sound, it is useful to take a 

close look at its principle. The following charts are over-simplified schematics that every one can 

understand, and will help you understanding why this circuit is different, and eventually to understand 

what the famous "Lead Leveller" is all about! 

� The problem to solve, when you want to design a compressor for the guitar, is a double problem: 

1. Act as a limiter during the first part of the note - a strong peak 

2. Act as a sustainor during the second part of the note - a slow decay 

The common compressors are limiters or sustainors, but none of them can perform correctly the two 

functions. The Rockman compressors can do it. 

It took several years before finding the perfect circuit, the challenge being to handle the transition 

between the two parts of the note - the strong peak then the slow decay. 

� Let's review step by step what the rationale was, and how SR&D started from the basic compressor 

of the Rockman headphone amps and finally developed the Rockman Guitar Compressor and its 

Lead-Leveller circuit. 

That's a gain stage, based on an OpAmp 

and two resistors. 

All you need to know is that the gain of 

such a circuit is equal to 1+R2/R1. The 

smaller R1 is, the larger the gain is. The 

larger R1 is, the smaller the gain is. 

A compressor is, basically, a gain stage 

with a variable gain. A circuit that has a 

high gain with low signals, and a low gain 

with high signals. 

Let's add a Field Effect Transistor (FET) to 

R1. If we apply a negative voltage Vg to 

the gate of this FET, its resistance Rt will 

increase, and the gain of the OpAmp will 

decrease. 

This circuit is called a Voltage Control 

Amplifier (VCA). That's a nice beginning for 

a compressor: if we find a way to generate 

the proper negative control voltage, our 

compressor will automatically adjust its 

gain as expected! 


This diagram shows what a basic diode 

can do with an audio signal: only one half 

of the signal goes through, and the positive 

half is cleared. 

That's not a control voltage yet, cause we 

still have those half waves, but we are 

getting closer to our objective: generate a 

negative direct current, proportionally to the 

strength of the audio signal. 

In order to clear these negative oscillations, 

we add a capacitor right after the diode. 

A capacitor has a natural inertia, and 

cannot follow the rapid voltage changes of 

the half-waves. The result is a continuous, 

constant voltage, which is 1) negative and 

2) proportional to the strength of the audio 

signal. 

We have our control voltage for the FET of 

the compressor! 

What we have here is very close to the 

simple compressor of the Rockman 

headphone amps. 

The diode and the capacitor are a 

feedback loop that sends a strong negative 

voltage when the input signal is strong, 

thus reducing the gain, and a low negative 

voltage when the audio signal is low, thus 

raising the gain. 

That's what we wanted to build! 

The common compressor stompboxes are 

all based on similar, simple circuits. They 

work, with more or less interesting results. 

The problem with these simple circuits is 

the fixed, constant release time. The 

associated problems are usually 

unpleasant pumping effects: the circuit 

cannot react the way it should, and some 

notes are loud when they shouldn't, or 

weak when they should be raised. 

In Tom Scholz's patent US 4,627,094, we 

can read that the release issue was not 

solved yet: a soft note following a loud note 

wouldn't be processed correctly. 


The problem with the guitar, and the 

reason why the other compressors cannot 

handle it correctly, is that a guitar note is 

made of a very strong peak followed by a 

long decay. 

The diagram shows the reaction of the 

compressor to a signal pulse: instant 

attack, constant signal, instant decay. 

Following the fast attack is easy, but the 

classic compressors have a constant 

release rate (blue curve) that doesn't match 

the guitar constraint: a fast release first, 

then a slow release. 

The objective is to have a two-steps 

release, as depicted on the green curve: 

that's what SR&D developed for the 

Sustainor, and that's what makes the 

Rockman Guitar Compressor different. 

The next step was to reduce again the fast 

release step for the guitarists who use 

ultra-fast tapping techniques: that's the red 

curve - the Lead-Leveller. 

In the Rockman Sustainor's compressor, 

the capacitor is discharged via a series of 3 

diodes and a LED. This trick allows getting 

the green curve, with a fast initial release 

rate followed by a slower second step. 

Note that this fast initial decay is also 

necessary to provide the long sustain that 

we expect from a compressor: that's 

another key quality of the Rockman 

compressor. 

This series of four diodes was the answer 

of SR&D to the transition between a limiter 

and a sustainor circuit, and this solution 

can be found only in Rockman 

compressors. 

The Lead-Leveller is a very subtle change 

in the circuit: the LED is just bypassed, in 

order to have an initial decay which is 

faster again. 

This operation is achieved by a J-FET 

switch: that's the famous "Double-IC" 

modification of the younger Sustainor 

200's... 

No need for a Double-IC in the Rockman 

Guitar Compressor: this J-FET switch was 

integrated in the design and didn't require 

this cumbersome modification. The Lead- 

Leveller is simply activated by a footswitch 

that bypasses the LED of the circuit. 


� A few words about the other features of the Rockman Guitar Compressor: if you look at the front 

plate, you will see two slider switches. 

One of them is used to bypass the unit, and also to activate a noise reduction circuit - a sort of 

simplified Smart Gate integrated in the compression circuit. This feature is extremely useful when the 

compressor is followed by a hi-gain saturation: all the compressors generate some noise (since they 

raise their gain when the signal is low), and this noise reductor avoids this trouble. 

The Guitar Compressor was completed by a two positions Treble Booster: at the maximum setting, the 

Guitar Compressor reproduces the classic Rockman CLN2 sound. That's why the Guitar Compressor 

can be considered not only as a compressor, but also as a substitute to the clean channels of the 

Rockman Sustainor. 


� The Guitar Compressor is honestly useless if you have a Rockman Sustainor: in a DI approach, it 

won't generate any sound that a Sustainor cannot create. 

If you don't have a Sustainor but have a Rockman Distortion Generator, the Guitar Compressor is the 

perfect add-on to your rig: one module for the distortions, and one module for the clean sounds. 

� As a matter of fact, the Guitar Compressor was really designed to be used with a guitar amp. I had 

really given up using compressors years ago, and didn't want to use one again: I was tired of all this 

noise, pumping, dynamics loss, etc... that the other compressors do. Then I purchased a Guitar 

Compressor, and completely changed my opinion about compressors: this unit is amazing, and really 

enhances the sound of the guitar without messing it up. 

� Limitations? No, the unit is perfect as is! 


� The Guitar Compressor is fairly rare: 2350 only were made, and it is pretty hard to find one. The 

price on the market is accordingly high, but it's only fair if you consider the quality of the unit. 

A unique device, actually the only compressor designed specifically for the 

guitar. If you need a compressor, this is the unit to buy and keep. 


Introduction 

SMART GATE 

� The Smart Gate is probably the Rockman item that has the best reputation amongst the non- 

Rockman owners. By definition, the Smart Gate has no sound, and is thus independant from the 

player's tastes and style. 

� There are basically three types of noise reductors. 

• The classic noise-gates - cheap circuits in a stompbox format 

• Rocktron's Hush and its follower, the ISP decimator 

• Tom Scholz's Smart Gate 

The classic noise-gates suffer from their simplicity, their main default being to completely cut the signal 

before the end of the notes. The Hush is based on a complex signal processing principle called 

"adapted filtering" - and on a dedicated chip that performs this function. 

� What Tom Scholz did was to focus on the most critical aspect of this "adapted filtering": in which 

frequency range do we have noise? Thats how he came to the Smart Gate principle: something 

simple and efficient that has the same result as more complex noise reduction processors. 



� The first Smart Gate was introduced in 1986 as a part of the Rockman Sustainor. This unit has both 

an input compressor and a distortion stage: the perfect combination to get a lot of noise! 

Tom Scholz worked on a circuit that would suppress the noise where it is generated: right after the 

compressor. This choice is weird, in a first approach (we are used to noise reductors that are placed at 

the end of the chain), but it was after all very smart, cause it leaves the distortion sounds totally 

unchanged, with all their harmonics. 

� In 1988 and 1989, SR&D issued three more modules - extractions and developments from the 

Sustainor: the Guitar Compressor, the Distortion Generator and the Smart Gate. While the circuit 

inside the Sustainor is fairly limited in scope (clear the noise generated by the compressor before the 

distortion stage), the rack-format Smart Gate was widely expended and is an outstanding general 

purpose noise-reductor, that can handle any situation. 


� Before describing how the Smart Gate works, let's take a look at what a classic noise gate does. 

These basic circuits are based on a comparator that turns the signal on or off, above or under a given 

threshold. The end of the long notes are of course cut, and you must tweak the threshold every time 

you change sound. 

� The Smart Gate is an extrapolation of the "adapted filtering" principle. Basically, this principle says 

that the noise is minimal when: 

• you amplify the signal in the frequency bands where there is something to amplify 

• you attenuate the signal in the frequency bands where there is nothing to be heard 


Applying this principle in conformance with its original mathematical definition is complex (that's what 

the Hush does), but since we are dealing with instrument audio signals, the problem can be simplified: 

1. A guitar audio signal is made of fundamentals (below 1300Hz) that are quite strong 

2. A guitar audio signal has also harmonics (above 1300Hz) that are quite weak 

3. A white noise is equally strong in the low and high frequency 

4. The signal to noise ratio is usually good below 1300Hz 

5. The signal to noise ratio is usually bad in the high frequencies, above 1300Hz where we have 

only harmonics 

� That's how Tom Scholz came to the concept of a variable filter that would always let the low 

frequencies (below 1300Hz) go through, and that would open or close above 1300Hz, depending on 

the actual input signal. 

� Such a filter is very easy to build: a capacitor, a resistor and a FET can do the job. The complexity 

of the Smart Gate circuit is not here: we need additional circuits that will detect the presence of highfrequencies, 

to open immediately the filter every time a new note appears. Then we need another 

circuit that will control the release time: the filter must be closed proportionnaly to the note decay, so 

that the gates closes slowly without cutting the end of the notes. 


That's what you have in the first Smart-Gate, as described in Tom Scholz's patent US 4,809,337. This 

circuit, after several modifications and improvements, corresponds to the Smart Gate of the Rockman 

Sustainor. 

� The rack-version of the Smart-Gate is an extension of this circuit. The 1300Hz filter can be set to 

1000Hz (Hiss mode), 500Hz (Mid-Hiss mode) or even 20Hz (Full-band mode). Note that in full-band 

mode, the Smart Gate clears not only the breathing noise in the high frequencies, but also the hum 

noise that can be present in the low-frequencies. You can at least play with single-coil pick-ups without 

this unpleasant rumble noise! 


� The original Rockman Smart-Gate is very rare (less than 2000 items!) and accordingly expensive. 

For those who cannot find one, Bob Cedro has re-created the Smart-gate in a stompbox format, with 

CMS components, for MXR: all the reviews confirm that this re-issue is as good as the original. 

A truly innovative and smart unit, based on a simple circuit that has the same 

efficiency as more complex devices. 


Introduction 

DISTORTION GENERATOR 

� Though the Distortion can be considered as a extract of the Rockman Sustainor, it has its own 

personality, and was not designed exactly for the same usage. 

It is often said that the DG has a richer sound than the Sustainor, and as a matter of fact, it is more 

versatile in the complete range of distortion sounds. 


� It seems that the Distortion Generator was created in order to place an economic unit on the 

market. 

Nothing new in the DG, compared to the Sustainor, and some features were willingly cleared from the 

design to cut down the cost. 

� The Distortion Generator was introduced in 1987, and was produced at least until the end of 1991. 

Just like the Sustainor, it has of course been revised several times, especially at the Autoclean level: 

just like the Sustainor, a younger unit is preferable to an older unit, at least for the Autoclean 

improvements. 



� The basis of the Distortion Generator is the structure of all the classic Rockman Amp sims: 

1. Compressor 

2. Distortion stage 

3. Cab sim 

� Between the compressor and the distortion stage, if we compare the DG with the Sustainor: 

• No Smart Gate (unfortunately) 

• No loop for an external pre-distortion EQ (unfortunately...) 

• A 3-bands pre-distortion EQ (hopefully!) 

While the Sustainor has only presets for its distortion sounds (EDGE, DIST, and a gain boost switch), 

the DG can be controled with the following sliders, all placed before the distortion: 

• The compressor's gain 

• A three positions gain switch called "distortion harmonics" 

• A bass slider (boost or cut) 

• A mid slider (boost only) 

• A treble slider (cut only) 

The combinations are endless, and allow tweaking the sound from a very subtle bluesy overdrive to 

the most crazy distortion lead sounds. 

� The DG has the two circuits created for the Sustainor: the Autoclean and the Phase Notcher, then a 

classic treble slider (to adjust the DG to the type of amp - PA or guitar amp) and an output volume. 

There is also a footswitch that will boost the sound by a few dB's, during a solo for example. 

� Let's review now the evolution of the DG between 1987 and 1991: I have actually identified at least 

four different versions, the last being of course the best one. 

� The picture shows two DG's: January (left) 

and February (right). 

They look similar, with some off-board wiring 

remaining in the January model, but several 

modifications were made in the design: the older 

model is slightly more noisy. 


� This picture shows a 1988 DG (right) and a 

1990 model (left) 

The PCB was entirely revised (it is much wider), 

and the sonic difference is very clear: the new 

DG's have more gain, are more silent, and have 

an Autoclean that works much better. 

There is no information about the precise date of 

this change, but it was probably in 1989. 

� The last modification occurred between 1990 and 1991: it was, of course, the Lead-Leveller 

function. The modification is almost nothing: a resistor instead of a LED in the compressor circuit, that 

reduces a little the release time of the compressor. 


� The DG can be used as an extra channel, either within a Rockman rig (in addition to a Sustainor) or 

with a guitar amp. It is really an amp sim, and must not be considered as a regular distortion pedal! 

The design of the DG being much lighter, most of the people consider that the DG has more gain and 

harmonics than a Sustainor. It is absolutely true, especially if you can find a recent DG: the sound is 

rich and creamy, with more sustain than the Sustainor. 

� The limits of the DG come from what was cleared in order to obtain a cheaper device: no Smart 

Gate, and no loop for an external pre-distortion EQ. I have corrected that on my September 1991 DG, 

and added the two features: my DG is now perfect! 


� There are over 15000 Distortion Generators on the market. It is not rare, and it is not expensive: 

two good reasons to buy one! The only difficulty is to locate a recent model, in order to have a good 

Autoclean: it's almost the same issue as chasing a good Sustainor 200. 

A very complete distortion unit, with a very wide versatility. A great addition to 

any rig. 


Introduction 

MIDI-OCTOPUS 

� If you never heard about the midiswitcher concept, you need to read this page. 

A midiswitcher is a non-audio device: its job is only to activate switches in order to control other 

devices. The midiswitcher itself is controlled via a Midi pedal board, or by any other device capable of 

sending Midi Program change orders. 

� The Rockman Midi Octopus is present in almost every Rockman rack: there are so many features 

to control when you want to change sound that the classic footswitches cannot handle that, unless 

you're a sort of tap-dance addict. 


� As long as the Rockmodules range was made only of the Sustainor and the Chorus/Delay, 

conventional footswitches were sufficient to control them: 1 channel change for the Sustainor, 1 

bypass for the C/D, and a third switch for the ChorusDelay change. 3 switches only. 

Then came the EQ's. Then came the Stereo Chorus with its 4 footswitches! A standard rockman rig 

(Sustainor, 2 EQ's, SC and SE) has a total of 10 controls that you are may want to switch every time 

you want to jump from one sound to another... 


That's how Tom Scholz decided to create something that would make all that mess programmable. A 

device that would turn off or on up to 8 switches when pressing a single footswitch. 

� The first prototype was a non-midi unit. A big pedalboard that could memorize the position of 10 

switches into 10 memories, each memory corresponding to one footswitch. Then 10 cables would run 

from the pedalboard to your rack's footswitches jacks: you could at the same time change the channel 

of your Sustainor, activate the Chorus, turn off the Echo and add an EQ by pressing only one 

footswitch. 

This prototype was presented in SR&D's 1987 catalogue, but was never issued as a commercial 

product. 

� In the meantime, the Octopus took a new orientation, and was in fact cut in two distinct units: the 

Midiswitcher and the Midipedal. 

The Midiswitcher contains the programmable features and the control switches, while the Midipedal 

only sends midi orders: the midiswitcher reads a Program Change number, and applies to the 

switches the configuration stored in its memory. 



� The best way to understand how the Midi Octopus is to read its manual. Just one comment here. 

The manual mentions that channel H has a relay - in case you want to switch something with a voltage 

difference issue. Well, I had something like 7 or 8 Midi Octopii in my hands, and only one of them had 

this relay (left picture), all the others having only a blank space (right picture)... 


� The Midi Octopus is almost mandatory if you have a real Rockman rig (6 modules or more). Several 

Octopii can be necessary for a very complex rig. 

� A lot of non-Rockman players use the Octopus to control their guitar amp, if this amp has a lot of 

footswitches, or simply to integrate a non-midi guitar amp within a global midified rig. 

� The Midi Octopus can also be completed with a cool accessory called "Remote Loop". This little 

Hammond box contains a relay and some jacks, and can be used to bypass a non midi stompbox, or 

as an A/B Box to control the signal path within a very complex rig. 


� The only limitation of the Octopus is linked to this relay question: if you want to switch another 

device that has a strong negative voltage in its switching circuit, the Octopus cannot handle it if it is not 

equipped with this small channel H relay. 


� The Octopus is not rare (over 6000 items), and is pretty easy to catch, though there are periods 

when it's almost impossible to find one! You may have seen on the picture that tops this page that the 

most recent Octopii had a different front-plate (almost entirely blue): these rare units correspond to the 

last year of production (1992). 

A mandatory tool for all the Rockman players, and a very convenient unit for 

anyone who wants to add midi control to his amp or set of pedals. 


DUAL REMOTE LOOP 

� The Dual Remote Loop is really a weird thing. SR&D produced a single batch of 50 of them: it is 

thus the rarest of all the Rockmodules! 

The Dual Remote Loop is basically a Rockmodule enclosure with a plastic (!) front plate, with the 

PCB's of two normal Remote Loops installed on the rear panel. 

� Try to buy one if you really want it: it's expensive, and it's a pure collector's choice... 



Introduction 

THE XP SERIES 

� A Rockman rig based on a series of Rockmodules is a very complex set-up: you rapidly have 

several tenth of sliders, switches and footswitches to operate before getting the sound you want. 

The microprocessors that were available in the eighties were not powerful enough to perform digital 

signal processing, but they could easily handle the control parameters of analog devices. 

The Rockman XP Series was based on this concept: keep the analog circuits of the classical 

Rockman units, and make them programmable. 


� The XPR was not the first product based on this principle: there were digital controlled analog 

preamps and effects before. 

But the XPR was certainly the first all-in-one unit: as a matter of fact, when you own an XPR, you don't 

need anything else to deliver the sounds you want, and you can store 100 different programmable 

sounds in it! That was quite innovative in 1989. 


� The first item of the XP Series was the XPR, the first 19' rack unit made by SR&D. It was replaced 

in 1991 by an updated low-noise version, the XPRa: 

� The basis of the XPR is just... the X100 headphone amp! In other terms, the XPR is a sort of big, 

programmable X100, with of course several additions that make it totally flexible: 

• There is a first 3-bands EQ at the input level, that allows shaping the distortion at will (refer to 

• The preamp and distortion stage have a cool feature that allows mixing a clean sound and a 

distortion sound 

• A 5-bands post-EQ is placed right after the distortion stage: the combination of pre and post- 

EQ gives the XPR a total flexibility in terms of sound 

• The stereo chorus has a programmable sweep speed (but no Long-Chorus mode) 

• The reverb section can be used as a short stereo delay 

� All the parameters of these modules (compressor, pre-EQ, preamp, post-EQ, chorus and 

echo/reverb) are entirely programmable, and can be stored in 100 presets. 


� The temptation was of course to build a guitar amp that would have an XPR as a preamp section. 

The guitar amp would of course be stereo, and stereo called of course for separable cabs for a wider 

image. That was the XP100 Programmable Stereo Amp: the XPR with a 2x50W stereo amp, housed 

in a double enclosure with compact 6 inches Pyle speakers: 


� The weakness of the XP100 is clearly its small speakers: the amp in itself is excellent and loud, but 

these small car-audio speakers cannot handle this power the way it deserves. The other amp based 

on the XPR was the XP212: a 2x50W stereo combo with two 12 inches guitar speakers. This version 

is extremely rare: probably a dozen of XP212 only were made. 

� The ad for the XP212 shows discretely another XP Series product, without even naming it! This is 

the more-than-rare Rockman Superhead: it is in fact the electronics of an XP100, presented in a head 

format. I have myself transformed an XP100 into a Superhead Replica, certainly because I will never 

cross a real one: Boston owns one of them, and a second Superhead was sold on eBay in January 

2006: that's all we know about it! Having no speaker, the Superhead must of course be connected to a 

pair of full-range cabs: it is loud, it sounds good, and it is in my opinion the best configuration for a 

XPR based Rockman amp. 



� The XPR is a contradictory product. It is programmable, and that makes it a fantastic unit, of 

course. The preamp and EQ's section is really great, and sounds really awesome. 

The chorus and reverb sections are of course weaker: they don't have the complex circuits of the 

Rockmodules, and are fairly limited and noisy. For example, the reverb section is based on the same 

MN3011 chip as in the headphone amps, and was pushed to its limits in order to obtain a 220ms (340 

in the XPRa) delay. It is noisy, and far from the plain and clean 500ms of the Stereo Echo. 

� All and all a good unit, the XPR delivers a wide panel of sound and atmosphere in a very compact 

and handy format. Had it been a preamp only, with the Autoclean and a built-in Smart Gate, it would 

have been almost perfect. But like every all-in-one device, it has some minor defaults. 


The XP products are quite rare: less than 3000 were built, most of them being basic XPR's or 

XP100's. The XPRa, XP100a, XP212 and Superhead are so rare that you must not plan to buy one: 

just catch it if you can when you see one! 

The XP products are very contradictory units, with fantastic qualities but also 

some weaknesses: some people will find them great, while others will be 

disappointed and prefer the classic Rockmodules. 


THE PGE-2 

� The PGE2 can be considered as the masterpiece of SR&D. Its technical characteristics are close to 

perfection, and its musical interest is amazing when you have understood what a pair of 14-bands, 

studio quality equalizers can do for a guitar sound. 

Certainly the most desirable of all the SR&D's products, the PGE-2 is extremely hard to find: 99 units 

only were made, Tom Scholz and Boston own a good tenth of them, 10 units were shipped to Europe, 

and another 10 to Japan. 

I'm the lucky and proud owner of the unit that was sold in France in 1991 (#23): it was a unique 

opportunity and I will certainly never see another one around here! 

� Just read the owner's manual, which says everything you need to know about the unit, and... look! 



THE PRO-BASS 

� This ad is unfortunately all that we know about the very confidential Pro-Bass rack. 

It does exist: Tom Scholz owns one for Boston, and some happy-fews managed to have it in hand. 

But only a handful were made, and the Pro-Bass is virtually impossible to find and buy. 

� As of what we can see on the front-plate, the basis is certainly the Bass Rockman headphone amp 

circuit, with additional filters and EQ's. 


AGP, UDG AND A12-50 

� The last products created by SR&D, in 1993-1994, clearly show a lack of inspiration and difficulties 

to follow the market trends. 

The digital era had begun, and the classic range of Rockman products didn't sell the way they used to. 

The response of SR&D was the economic Ace series for the headphone amps, and a new circuit that 

could have become a reference: the Ultimatum Distortion. 

This revolutionary distortion circuit is based on two distinct clipping stage in series. 

The first part of the Ultimatum circuit is similar to what you find in the classic Rockman unit: 

compressor, clipping stage and cab sim. 

A second clipping stage was added, that simulates the saturation of a power section in an overdriven 

tube amp. 

The result is extremely realistic, with a rich a plain sound, full of sustain and harmonics. 

� The Ultimatum circuit should have been issued as a programmable rack: a sort of super-Sustainor, 

merging the features of the XPR, the Sustainor and the Ultimatum circuit. This would have been a 

fantastic unit, but the product was only made as a prototype, as of Rockman-Central. 

The circuit ended into a stompbox format: that was the UDG... It's clearly an outstanding pedal, 

something that you keep because you just love it: you only miss that it was never issued in a rack 

format! 

The UDG sounds great as a DI unit, and can also be used in front of a guitar amp with fine results. 


� SR&D made another pedal in these last two years: the weird Acoustic Guitar Pedal. 

The AGP is basically a compressor with bass and treble controls: if you compress a lot, then find the 

sweet spot on the treble pot, your electric guitar will ring the same way as an acoustic guitar. 

Don't expect the AGP to make your Les Paul sound like a Martin's or a Guild! The AGP is an 

extrapolation of the classic Rockman CLN2 sound, and aims at simulating the position of an acoustic 

guitar in a mix, more than its sound itself. 

Note that the AGP was re-issued by Dunlop in 1996, to answer the request of their japanese 

distributor. These re-issues can be recognized by their blue button, the original SR&D AGP having a 

grey button. 

� The Ultimatum circuit was also used in another weird Rockman product: the A12-50 combo. Yes, 

the last product of the brand who had proved that one could play guitar without an amp was... a guitar 

amp! 

� This small 50W combo is actually an excellent solid-state amp, with a sound and power that can 

easily be compared with its tube competitors: I've been playing with a Boogie for 20 years, and several 

side-by-side comparisons proved that the Ultimatum Distortion, coupled to the excellent Celestion 12' 

speaker of the A12-50 give results of a similar quality. 


Footswitches 

ACCESSORIES 

� SR&D used to sell various accessories to complete the headphone amps, and the Rockmodules 

during their first years. 

If you are lucky, you may find one of these rare Rockman Single Footswitch: built as a rock, universal, 

it has a battery inside that powers a green and a red LED - thus indicating if the switch is on or off. 

It cannot start the engine of a Harley, but it's certainly because there is no footswitch jack on the bike! 

� The single footswitch was extended to a Triple Footswitch: the robust steel enclosure has the same 

profile as the Single Footswitch, and as shown on this graphics, the principle was kept for the 

Midipedal and the late Stompboxes. 


The Rockman Triple Footswitch is a funny device that has a specific feature: it has an internal 

electronic timer, powered by four D batteries, that turns off the LED's after 15 minutes... 

Headphones 

� The Headphones amps accessories are difficult to find (they were rather fragile and aged badly). 

The headphones have disappeared most of the time, and finding original an SR&D headphones set in 

good shape is getting tricky. 

Note that the Bass Rockman headphones are different: they can be recognized by their white logo, the 

guitar headphones having a black logo. 

Power-supplies and Rockadaptor 

� The headphones power-supplies are specific to the Rockman line: they are balanced +/-6V 

wallwarts that don't have a standard replacement. 


� There are two types of wall-warts. Here's the older model with its Rockadaptor (blue logo in the first 

years, then white logo). In these older models, the voltage regulation circuit is inside the Rockadaptor, 

and the wall-wart is directly connected to the Rockadaptor. 

� In 1986, SR&D added a TRS mini-jack on the headphone amps for the power-supply, and the 

wallwart had of course a male TRS jack. The Rockdadaptor was not discontinued, but these new 

items were just empty plastic adaptors with only a female TRS jack: they were used by people who 

owned an older Rockman. One could finally buy separately the wall-wart and the Rockadaptor. 



STAGE GEAR 

� How did a brand like like Rockman, the brand that had created the DI concept, come to selling the 

biggest guitar amps ever built? 

The basis principle of the Rockman approach is to play without an amp. 

Yet, Tom Scholz has created this product line for Boston, and Boston is not a band that only records in 

a studio: Boston plays live on stage, on very large stages. 

� The stage gear of Boston was designed strictly for the show: these huge amps and cabs are in fact 

totally useless (they are not miked), but are big enough to give an exiting look to the band during the 

shows. 

The 3-way cabs were made specially for Boston, in the same spirit as the cabs of a front PA system: 

they are totally linear, unlike conventional guitar cabs which colorate the sound a lot. 

� As for the amps, the famous Rockman PA500 is a Carver PM175 2x250W, with a Rockman front 

plate and a small modification: the input is copied to a pair of jacks, used to send the signal to the 

main PA mixer. 

� This stage equipment (cabs, amps and stagehead) were made available as commercial products, 

but were produced in very limited quantity (50 or so, as of Rockman-Central). 

They are of course highly praised collectors items... 


APPENDICES 


� The data in these tables are: 

PRODUCTS LIST 

• For the original SR&D sales price, based on Rockman-Central information, completed or 

amended by ads published in magazines in the 80's and 90's. 

• For the production dates, either Rockman-Central data, either deduction made by analysing 

various schematics, ads and SR&D documents. 

• For the production quantities: Rockman-Central has published detailed data about the Stage 

Heads and the Rockmodules. As for the other items, the quantity estimations are based on 

actual number of transactions, analysed over a period of sixth months on eBay. This rotation 

analysis, matched with the quantities that are known for some items, allowed computing a 

"probable" production quantities for the other products. 

� The last colums give an indication about the collectibility and interest of each item. These 

information cannot, of course, be totally objective, but I have followed simple rules to provide useful 

guidelines to someone new to the Rockman gear. 

Interest: some SR&D products are really unique, and no other brand has produced a similar item. On 

the other hand, some items are truely common and can find easy replacements : think about the 

single footswitch, which has nothing special, though it's a rare, collectible item for Rockman 

afficionados. 

Collectibility. Rockman collectors usually merge three approaches during their chase for gear: Boston, 

technical aspects and rarity. The PGE2 is the perfect example of an extremely rare item, having 

amazing technical characteristics, being used on stage by Boston. That makes the PG2 one of the 

most desirable Rockman item (though it's not stamped "Rockman"...). On the other hand, a cheap and 

common Guitar Ace, that has been re-issued by Dunlop, is not considered as interesting by the 

collectors. Still, it's a quality product that was used by Deff Leppard on all the tracks of some of their 

albums... 

Collectibility 

A Rare and desirable, hard to find and buy 

B Hard to find, but not rare 

C Common item, easy to find and buy 

Interest 

A A reference in its category 

B A matter of taste... 

C For collectors only 


Stage heads and stacks 

� These stage heads, stacks and cabs belong to the Rock'n'Roll History. Originally designed for 

Boston, you may cross one of them: they are priceless. Just have in mind that Rackmount Concepts 

builds excellent replicas at a more than affordable price! 

Note that less than 50 complete Rockman stacks were actually produced (hence less than 50 PA500). 

The exact distribution between the various head types is unknown. 

Quantity Start End List Price Collectibility Interest 

DC 500 (DG+SC) 10 ? 1989 $1 460,00 A+++ B 

S12 CE 500 

(SP+EQ+SC+CE) 

10 ? 1989 $1 875,00 A+++ B 

SC 500 (SP+SC) 10 ? 1989 $1 540,00 A+++ B 

SD12 CEM 500 

(SP+DG+EQ+SC+SE+MO) 

10 ? 1989 $2 265,00 A+++ B 

PA220 2x110W Power amp A+++ C 

PA500 2x250W

Special non-commercial item 

� The Rockman Demo-center was designed for music-shops willing to demonstrate the Rockmodules 

in a compact, convenient format. Included are a Sustainor, a Distortion Generator, an Instrument EQ, 

and a Stereo Chorus and Stereo Echo. The Demo Center had switches allowing comparing the 

various sounds, and was equipped with a pair of active speakers mounted on the left and right side of 

the unit. 

Two types of Demo Center were produced: some with all the modules at the right side, and a onepiece 

cache on the left, and others with the Rockmodules alternating left and right position, with half 

rack separate cache metal plates. 

� The demo Center is very rare, and is a nice rig to have at home when you like the Rockmodules. 


Rockman demo-center

Rockmodules 

� Information about the Rockmodules is precise and reliable, thanks to Bob and Curt at Rockman- 

Central. The quantities here are from R-C, except for the DG: Curt confirms that "There were more like 

15000 Distortion Generators" and I actually own the DG #15325, dated Sept 1991. 

Prices are pretty stable, and if the buyer and seller both know their role, transactions are smooth and 

easy. 

Sustainor 100 11000 Jan. 

1986 

Sustainor 100A 3000 Mar. 

1987 

Sustainor 200 5700 Sep. 

1987 

Sustainor 200 Double IC 1700 June 

1989 


Apr. 

1987 

Sep. 

1987 

May 

1989 

May 

1992 

$289,95 C B 

$289,95 B B 

$349,95 A A 

$349,95 A++ A 

Stereo Chorus Delay 6800 1986 1987 $249,95 B A 

Distortion Generator >15000 1987 1991- 

92? 

Instrument EQ 8000 1987 1991- 

92? 

Stereo Echo 6700 1987 1991- 

92? 

Stereo Chorus 6765 1987 1991- 

92? 

Midi Octopus 6200 1988 1991- 

92? 

Guitar Compressor 2350 1989 1991- 

92? 

Smart Gate 1940 1989 1991- 

92? 

$169,95 C A 

$199,95 A A 

$249,95 A++ A++ 

$169,95 A A+ 

$239,95 A B 

$129,95 A A 

$129,95 A++ A 

Dual Remote Loop 50 1991 1991 $129,95 A+++ C 

Rackmount (racktray for two 

modules) 

1986 1991- 

92? 

$19,95 A A 


Rockman headphone amps 

� The Rockman headphone amps were produced by thousands, and can be found very easily. Some 

sellers try to hit the big money with them, but to be honnest, they became very cheap now and there is 

no reason why you should spend a fortune in something that sells by tenth every quarter. Clearly 

prefer a recent item: SR&D was continously improving the products, and the best headphone amps 

are the younger ones. 

Accessories are quite hard to find, so prices can be surprising sometimes... 


Rockman 8000 ? 1982 1984 C B 

Ultralight

Rare accessories 

� You can see some of these for sale, from time to time. They are rare items, thus making them 

desirable if you are addicted to Rockman gear. Note that the Remote Loop allows controling any 

stompbox via a Midi-Octopus. 


Remote Loop

PRESS REVIEWS

Rockman : The Products - Rockman - By Tom Scholz

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