Wayne Donnelly - Audio Tweak

Spectron Audio Musician III
Raising the digital bar.
Review By Wayne Donnelly
Digital power amplification has been around for quite a while, and recently a number of new
marques have hit the marketplace, typically offering higher power output per dollar than
traditional solid-state and tube amplifiers. This writer has not yet had a chance to listen
carefully to any of those 'Class D' newbies, but for the last three months I have been having
loads o' fun with the latest offering from a grizzled veteran of the digital amplifier wars,
Spectron Audio.
Few if any audio designers can match the engineering experience and credentials of John
Ulrick, Spectron's founder, chief designer and CEO. Ulrick co-founded (with Arnie Nudell)
Infinity back in 1968, and designed the digital servo-amplified subwoofer that launched that
company. He designed his first Class D amplifier in 1974. His latest offering, the Musician III,
presents a formidable challenge not only to other Class D contenders, but also to top-rank
power amplifiers of every type.
The 500 watts-per-channel (into 8 ohms) Musician III occupies a modest-sized chassis about
the size of a typical 100 wpc solid-state amplifier. But don't be fooled. This thing is capable of
brutal power into low-impedance loads that could defeat or even destroy many power
amplifiers. Output into 4 ohms is listed conservatively as 700 continuous wpc, and John Ulrick
informs me that the amplifier can deliver a sustained1,400 wpc into a 0.5-ohm load. It is
difficult to conceive of any home loudspeaker that the Musician III could not comfortably drive
to thunderous volumes. And, not surprisingly, Spectron OEMs the power modules used in the
Musician III for use in pro sound applications where very high power and bulletproof reliability
are essential.
Technical Highlights
The Musician III is in many respects a technical tour de force. I asked John Ulrick to identify
those qualities that contribute most significantly to the amplifier's superb sonic quality, and the
suggested these five:
Closed loop with fast response time: Feedback corrects for errors in the output. In
amplifiers with transformer output or slow analog circuitry, application of fast, highperformance
feedback loop correction is less than optimal. In Spectron amplifiers the
feedback loops are about ten times faster than in conventional amplifies. Spectron asserts
that this ultra-fast correction makes its amplifiers superior at capturing fine details in the music
signal.

Isolated low-level power supplies: Over the years, some preamplifier designers have gone
so far as to use batteries to achieve isolation from the AC mains. To achieve the same effect,
Spectron employs a micro-sized switching supply for the +15V that operate the low-level
amplifier and the digital logic. This design is about 500 times more isolated than the
conventional method of taking power from a 50/60Hz transformer. As a result, the new
Spectron amplifiers are far less in need of power conditioning or premium power cords in
order to sound their best.
Floating RCA inputs: Ground loops have always been a problem in audio. They may show
up as obvious buzz from speakers with no music playing, or as more insidious hum that rises
with increasing loudness. Even when masked by the music, this hum can make music sound
less natural and detailed. The Musician III's balanced XLR inputs are not susceptible to
ground loops. When connected via single-ended interconnects, the Musician III's floating RCA
inputs eliminate ground loop buzz and hum.
Power capacitors: To store energy between each cycle of power from the 50/60 Hz power
lines, all amplifiers use energy-storage capacitors. Most amplifiers have one big capacitor for
the + supply and a second for the - supply. The Musician III uses separate banks of
capacitors for the left and right channels, emulating a dual mono topology. Those banks of
small capacitors provide a lower-impedance supply to each amplifier module than one big
capacitor can achieve.
High-output voltage and current: A power amplifier's ability to drive loudspeakers is based
on its supplying ample voltage and current. When the amplifier runs out of voltage, it voltage
clips; when it runs out of current, it current clips. With the Musician III's very high peak voltage
of 110 volts and peak current of 50 amps, neither voltage nor current clipping is likely in a
home music system. Despite numerous excursions into unwisely loud listening levels during
the review period, I was never able to push the Musician III into audible clipping.
In addition to the preceding highlights, there are a couple of other features that distinguish the
Musician III from most other power amplifiers. Any audiophile who has ever shorted out a big
amplifier knows what a heart- sickening phenomenon it is — likely to involve loud pops,
electrical flashes and smoke, followed by deadly silence and lingering bad smells. The
Musician III is blessedly immune to such destructive blowups — a comforting thought when
running such high power into your precious loudspeakers.
With the fold-back current limiting implemented in the Musician III, if the amplifier is
overdriven to the 50-Amp peak current limit, it will continue to deliver 50 Amps for half a
second. It then automatically reduces the output current to 15 Amps over the next half
second, and maintains the 15 Amps until the load returns to normal. The practical effect is
that shorting out the Musician III won't hurt it. And if you have "amp-killer" speakers — like the
infamous Infinity Kapa 9s, which go below one-ohm impedance — you can play them loudly,
and you probably won't even hear when the current limit kicks in. The Musician III won't just
shut down at too-high current levels as other amplifiers do.
Unique to Spectron is the Remote Sense speaker cable system, which is designed to
eliminate sonic degradations caused by the musical signal passing through various types of
loudspeaker cables. For $595/pair, Spectron supplies special four-conductor cables; two
conductors carry the musical signal, while the other two feed back to the amplifier output
terminals. They connect to the amplifier via twist-to-connect SpeakON connectors.

The concept here is to extend the amplifier's global feedback network in order to correct
signal errors all the way out to the end of the speaker cables — in contrast to all other
amplifiers, whose control of the signal ends at the cable. Unfortunately, I was unable to
thoroughly evaluate this feature in time for this review. I will publish a follow-up in the near
future to address the comparative performances of Remote Sense versus conventional
premium loudspeaker cables.
In addition to all of the features described above, the Musician III incorporates fault sensing
(of excessive DC or high-frequency output) protection and reset, over/under voltage
protection, and thermal shutoff and recovery. In short, the brute power of this amplifier is well
fortified against virtually any possible malfunction.
Exterior Tour
The silver-toned fascia features horizontal grooves and an oval-shaped, blue backlit center
portion. The on/off pushbutton at the lower left is the only front control. The rear panel
comprises the fault indicator and reset, the IEC jack, and for each channel one set each of
XLR and RCA input jacks, one set of the terrific-sounding Eichmann 5-way speaker terminals,
and one SpeakON connector. There are also two pairs of switches, for selecting the desired
input and for reversing the amplifier's phase. Everything is clearly marked and well laid out.
Review Setup
Most of my time and energy from Spring 2005 to the present has been taken up with
transplanting my life from suburban Mountain View, California to Chicago's South Loop. This
review is my first to be based entirely on the excellent listening room of my new home, a
spacious 12 th -floor condo in an 1891-vintage building. My system now resides in a 23' x 15' x
9 1/2' room with hardwood floor over 12" of concrete (same for the ceiling). Happily, it is
proving to be a fine space for a good audio system.
The Musician III has been auditioned for three months in my reference rig: VTL 7.5 line
preamplifier, Modwright/Denon 3910 all-format player (review coming), Thor TA-3000 Mk II
phono stage, Basis 2800 vacuum turntable, Graham 2.2 arm/Transfiguration Temper
cartridge, mostly Bybee cables. For the first couple of weeks I listened to Meadowlark Blue
Heron 2 loudspeakers; after that, the Analysis Omega planar/ribbon loudspeakers (also
reviewed in this issue.)

Listening
High-powered amplifiers are familiar ground to this writer. For the last few years, my everyday
amplifiers have been successive iterations of the 750-watt VTL monoblocks. I expected a
quite different sonic presentation from the Musician III, and that proved to be the case —
although the digital amplifier was surprising in several respects.
The Musician III from the beginning exhibited a very wideband, high-speed musical
presentation. That in itself was no surprise. What is surprising is, first, that it sounds more
extended in the high frequencies than any amplifier I have had in this system, solid-state or
tube. And secondly, that extraordinary treble extension is remarkably free of the tonal
brightness, the glare and grain that have marked my listening experiences with so many
transistor amps over the years. The neutrality was so pronounced that it took me a few days
to become accustomed to it. And as the amplifier burned in, that extended but smooth and
relaxed quality grew even more natural sounding. The highs took on a lovely, crystalline
quality, somehow unlike other amplifiers I can recall. Perhaps the closest comparison I can
think of for this degree of tonal purity is with the 55 watt WAVAC MD-805 monblocks I
reviewed last November.
I expected very deep and powerful bass, and half-expected it to be the kind of "slam" I
associate with Krell and a few other marques (and which I tend to find exaggerated). In fact,
the bass of the Musician III has a full measure of low-frequency depth, speed and pitch
definition. Equally as important for me, its scaling of dynamics seems flawlessly accurate,
from bass drum thwack to the triangle's strike and decay, and everything in between.
As I mentioned at the beginning, this is my first review to be based entirely on listening in my
new Chicago music room, which is clearly superior to the room I used for the past 15 years in
California. That factor notwithstanding, I feel confident stating that the spatial resolution of the
Musician III is outstanding. Playing the finale of Mahler's Resurrection Symphony (Michael
Tilson Thomas leading the San Francisco Symphony, soloists and Chorus), the spatial
organization of these gigantic performing forces is more clearly delineated than ever before.
Yes, the chorus are obviously ranged behind and surrounding the instruments. But the depth
of the soundscape is greater than I have heard before on this very familiar recording. In
addition, the placement of individual players — solo oboe firmly in the middle of the orchestra,
trumpets clearly at the rear; soprano and mezzo soloists clearly separated from the chorus,
even when they are all singing together — is uncannily precise. It's as if my listening room
has morphed into Davies Symphony Hall right in front of me.
As I play more and more familiar recordings, I am stunned by how faithfully the ambiance of
each recording venue is captured. I can easily distinguish between closely and distantly
recorded piano, between jazz in a club versus a larger venue. And so forth...

Summing Up
Here is where I typically recap the pros and cons of the component under review and express
my opinion about its value in relation to price and competition. In this case I am hard pressed
to find the cons. I can imagine that some hard-core tube lovers may find the Musician III's
harmonic envelope slightly lean — lacking that sweet second harmonic that tubes do so well.
But I think this amplifier's harmonic presentation is honest and robust, more complete than
most transistor amplifiers I've encountered.
A couple of years back, I most enthusiastically reviewed the massive John Curl-designed
Parasound Halo JC-1 400-watt monoblocks, which I have since regarded as the best solidstate
amplifiers I have experienced. At $6,000 per pair, they seemed to me a great bargain.
Now, after the lapse of time since that review, I cannot say authoritatively that the Musician III
sounds even better, but I think it very likely does. At the least it's a close call. And I have no
qualms about pronouncing the Musician III a tremendous value. Anyone looking for powerful
yet highly refined amplification would be foolish to ignore the Spectron Musician III. I believe it
will serve me well as a standard against which to measure other amplifiers. So I'm keeping
this one. Superior audio indeed!
Specifications
Type: Stereo amplifier
Frequency Response: 20Hz to 20kHz ( ±.1dB) at 8 Ohms
Power: 4 Ohms 700 wpc, 8 Ohms 550 wpc, and 1,400 wpc at 2 Ohms
Maximum Output Current: 50 Amps peak
Max Output Voltage: 110V
Damping Ratio: 400:1
Distortion, THD: