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The serious music lover wants an audio system that

will reproduce the original musical performance

with as much fidelity as possible. Each component

must either pass signals without adding coloration,

or must provide just the right amount of compensation

to previously modified signals. The SU-7700

performs these functions beautifully. While its

most apparent attributes are excellent specifications

and elegant styling, it can be fully appreciated

only when heard with other components of equally

high quality. The transparent and "effortless"

rendition of very demanding program material

will delight even the most critical listener.

50 watts per channel, minimum RMS, both channels driven, at 8 ohms

from 2OHz to 2O kHz,with no more than O.O8o/o total harmonic distortion.

At 1,OOOHz, this figure rises to S3watts per channel at 8ohms.

Power When You Need lt-Fidelity Always

50 watts per channel, minimum RMS, both

channels driven, at 8 ohms, from 20 Hz to

2Q kHz, with no more than 0.08% total

harmonic distortion. That says it in a

nutshell, but have you considered what

this performance means for practical

listening enjoyment? SuPPose Your

speakers are low-efficiency, or that you

want to drive two pairs at once. Suppose

your musical tastes run to popular music

irvitn a lot of floor-shaking low bass'

Under most conceivable home listening

situations, the SU-7700 will provide all

the power you need. But the real

accomplishment of Technics engineers

has been to hold total harmonic distortion

down to 0.08%, and to control this rather

awesome power right down through the

lowest audible lrequencies, so power

bursts won't create transient distortion

that can momentarily degrade fidelity.

Combined with other components ot equal

oualitv, vour SU-7700 will provide power

virnen'it's needed, and muiical fidelity all

the time.

Current Mirror Loading Attains Extremely High S/N Ratio in Equalizer and Low Distortion

in Power Circuits

A classic dilemma in amplifier design is to By virtue of current mirror loading, the

achieve higher operating current (for gain) gain producing effect of a given operating

without a correspondingly higher level current is magnified. The results are a

of noise. To solve this problem, Technics higher S/N ratio in the equalizer and a

has employed current mirror loading in lower distortion rating in the power

the dilferential amplifier first stage of the amplif ier.

equalizer circuit and the power amplifier.


S/N Ratio al 2.5 mV Phono lnput


The 78 dB phono signal-to-noise ratio is

the equivalent of a 1/8,0001h noise

component in the music signal. In real

terms, this means that on well cared-for

records, noise won't interfere with your

enjoyment of the music, even during very

soft passages. Significantly, the S/N ratio

should be even better than 78 dB with

high output cartridges, as this figure was

obtained at a relatively high sensitivity

level of 2.5 mV.

This extreme

"quietness" of the

phono equalizer is

the result of

advanced current ffi,:'"

mirror circuit

design and

use of low

noise lC.


Total Harmonic Distortion

(20 Hz-20 kHz) at Rated oulput

In hi gh-f idelity amplif iers, only distortionfree

power counts. At any power level,

from a whisper to the roar of the full

50 watts per channel, the total harmonic

distortion of the SU-7700 never exceeds

an imperceptible 0.08%, and is typically

much less. Note, too, that this also applies

to the entire range of frequency response,

from 20 Hz to 2O kHz. Use of matched

transistor pairs in a single package and

already mentioned

current mrrror

loading contribute to

this low distortion

f igure.

Single packaged pair


Subsonic Equalizer Filter

A subsonic f ilter in the NFB loop of the

phono equalizer removes inaudible but

nevertheless troublesome ultra-low

frequencies which could cause intermodulation

distortion in conventional

circuits. Rumble, low-frequency noise

resulting f rom warped records, as well as

tonearm/cartridge resonances are cut off

at the source with a steep 12 dB/oct slope

below 30 Hz. Typically, a resonance peak

of the tonearm/cartridge assembly appears

in the 5 Hz to 10 Hz area, as shown below.

It is clearly noticeable as a useless

"pumping" movement of the woofer cone.

Cut-off at the input means that such

subsonic "garbage" can do no harm at any

downstream signal stage. Conventional

subsonic filters, on the other hand, are

inserted into the preamplif ier after much

of the intermodulation has alreadv been


RIAA Gompensation Accurate Within

*0.2 dB

The playback equalization characteristic

of the SU-7700 varies by only +0.2 dB

(30 Hz-15 kHz) from being a perfect

inverse of the RIAA recording characteristic

for phonograph records. In the past,

precision of this order would have been

difficult to find even in very eixpensive

amplifiers. We achieved it through use of

+1ok tolerance metallic f ilm resistors and

+2o/o polypr opylene capacitors.

Two-Way Dubbing

The tape selector circuit permits two tape

decks to be connected at the same time to

the SU-7700. Dubbing may be performed

between the two decks in either direction.

Additionally, as the tape monitor and

recording mode switches operate

independently, you can use the SU-7700 to

listen to a record or FM program while

tape dubbing is in progress.

41 Step Volume Control

To provide precise, repeatable volume

settings, the volume control has 41 clicksrops.

Tone Controls with Deleat at "0" Position

Using-newly developed controls, the bass

and treble control circuits are disconnected

lrom the main circuits when the respective

control knob is set at the center ("0")

position. ln this state, the main circuit is

reduced to an equalizer amplifier, plus a

power amplifier- the simplest possible

circuit, and one in which potential sources

of distortion are minimized. When the

tone controls are used, their negative

feedback circuits provide low distortion

equalization that would be considered

excellent by any standards. With these

controls, equalization is variable over a

wide range of +12 dB.

High Filter

Cuts out high frequency noise such as

record scratches and taoe hiss.

Direct Reading Power Meters

The large scale meters provide direct

readout (at 8 ohms) of amplifier output

power in watts, with instantaneous tracing

of signal peaks. To improve linearity at

low output, a germanium diode is used for

rectification. Two ranges are provided

(x1 and x0.1) for accurate monitoring of

all output levels.

Muting Circuit Eliminates Power On/Off

Switching Noise

To eliminate the unpleasant noises which

are heard from the speakers when power

is turned on or off, the SU-7700 is

equipped with a muting relay which

operates in conjunction with a protective

circu it.

Stabilized Power Supply

To insure that adequate power, at constant

voltage, is available for every output

requirement, the SU-7700 features a

balanced positive-negative power supply

using transistors and zener diodes.

Main/Remote Speaker Facililies

Two pairs of speakers may be connected

and fed separately or together. Two

pushbutton selectors permit operation of

main speakers only, remote speakers

only, or'both pairs simultaneously.

Heat sinks

Electrolytic capacitor


Power transistors

Power transformer

Protection relay and

pop noise muting circuit

Current mirror loaded

differential amplif ier

Low noise phono equalizer circuit

1. Power on/olf switch

2. Phones jack

3. Main sDeaker switch

4. Remote speakers switch

5. Meter range seleclor

6. High filter switch

7. Loudness switch

8. Bass control

9. Treble control

Technical Specifications

10. Mode selector

11. Rec/Mode selector

12. Taoe monitor switch

13. Inout selector

14. Equalizer subsonic lilter switch

15. Volume control

16. Balance control

17. Direct reading power meters


Ground terminal

2. Phono inputs

3. Tuner inputs

4. AUX inputs

5. Tape deck 1, REC outputs

6. Tape deck .1, PLAY inputs

7. Tape deck 2, REC outputs

8. Tape deck 2, PLAY inPuts

9. REC/PLAY terminal

(tape deck 2)

10. SDeaker terminals (main)

11. Soeaker terminals (remote)


1 kHz continuous power output

both channels driven 2 x 70W (4o)

2x53W (8o)

40 Hz-16 kHz continuous power output

both channels driven 2x60W (4o)

2x50W (8o)

20 Hz-20 kHz continuous power output

both channels driven 2 x 60W (4o)

2x50W (8o)

Power bandwidth

both channels driven at 4rl

I Hz-55 kHz, -3 dB

Total harmonic distortion

rated power at 40 Hz-16 kHz, 4a 0.08%

rated power al 1 kHz,4a 0.08%

-26 dB power at 1 kHz,4a 0.1%

50 mV power at 1 kHz, 4a 0.15%

lntermodulation distortion

rated power at 250 Hzi I kqz=4:1, 4a


Frequency response

5 Hz-80 kHz, -3 dB

10 Hz-40 kHz, - 1 dB

Damping factor

50 (8o), 25 (4o)

Input sensitivity & impedance


2.5mV147 ka


150mV/47 ko


150mV/47 kfl

PLAYBACK, TAPE 1 180mV/47 ko

PLAYBACK. TAPE 2 150mV/47 ko

REC/PLAY, TAPE 1,2 180mV/47 ko

PHONO maximum input voltage


(1 kHz, RMS)


rated power PHONO


-26 dB power PHONO


50 mW power PHONO


63 dB

83 dB

55 dB

58 dB

53 dB

53 dB

Tone controls

BASS 50 Hz, +12 dB--12 dB

TREBLE 20 Hz, +12 dB__12 dB

EQ subsonic filter 30 Hz, -12 dB/oct

High filter

8 kHz, -6 dB/oct

Loudness control (volume at -30 dB)


Hz, *8 dB

Output voltage & impedance

REC OUT, TAPE 1, 2 150mV/1.2ka

REC/PLAY output 30mV/82 ko

Load impedance

MAIN or REMOTE 4-16o



Power consumption


Power suppfy 110V/120V1220V1240V

50/60 Hz

Dimensions 4'10 x 139 x 334 mm

(WxHxD) (16t"x5+*"x13+")


9.7 ks (21.4 lb.)


1 kHz continuous power:

both channels driven 70W+70W (4o)

53W+53W (8o)

2O Hz-20 kHz continuous power:

both channels driven 60W+60W (4o)

50W+50W (8o)

Total harmonic distortion:


(rated power, 20 Hz-2O kHz)


(half power, 20 Hz-20 kHz)


(half power, 1 kHz)

lntermodulation distortion: 0'08%

(60 Hz: 7 kHz=4:1, SMPTE)

Power bandwidth:

(both channels driven at 8f,)

8 Hz-55 kHz, -3 dB

Residual hum and noise:


Damping factor:

50 (8o), 25 (4a)

Load impedance:

MAIN or REMOTE 4-16a



Input sensitivity and impedance:


2.5mV/47 k0


150mV/47 ko


180mV/47 ko



150mV/47 ko

180mV/47 ko

PHONO maximum input voltage:

(1 kHz, RMS) 150mV

Signal/noise (lHF A):



Frequency response:



8-16o Tone controls:


50 Hz. + '12 dB- - 12 dB

TREBLE 20 kHz, + 12 dB-- 12 dB

Loudness control (volume at -30 dB):


78 dB

97 dB

standard curve +0.2 dB

5 Hz-80 kHz,

+0 dB, -3 dB

20 Hz-20 kHz, +0.5 dB

Hz, +8 dB

Filter :

EQ SUBSONIC 30 Hz, -12 dB/oct


8 kHz, -6 dB/oct

Output voltage:

TAPE'DECK 1.2 REC OUT 150mV/1.2 ko


Somvtaz xo


Power consu+nption:


Powersupply: 110V/120V1220V/240V

50/60 Hz

Dimensions 410 x 139 x 334 mm




9.7 ks (21.4 lb.)


Matsushita Electric

Specifications are subject to change without notice' Printed in Japan

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