Audio Database

SY-77
Commentary

A preamplifier with a simple circuit configuration that emphasizes characteristics and sound quality without sacrificing functions.

The circuit of the SY-77 is designed so that a high voltage of ± 70 v can be applied with two positive and negative power supplies, ensuring sufficient margin for the first stage of the system.

The flat amplifier section has a first stage cascode connection and a two stage differential pure complimentary service circuit. The configuration of the flat amplifier is similar to that of a power amplifier, so that the characteristics of an EQ are fully exhibited.
The output stage is a class A parallel push-pull operation, and the output impedance is set to 600 Ω to minimize the characteristic change due to connection.

The tone amplifier section also employs a two power supply configuration, positive and negative. It pursues a low distortion rate and stable operation. It is designed for sound quality in terms of audibility, with the first priority being that the quality does not deteriorate due to the insertion of the tone circuit. The circuit configuration employs a two stage direct-coupled active broad circuit including one stage differential. In addition, the volume uses a one step 2 db detent volume for precise adjustment.
The tone circuit can be disconnected by switching the switch.

A separate power supply is used for the power supply part, and interference between channels is eliminated by making the transformer winding independent on the left and right.
The power supply to the equalizer, flat amplifier, and tone amplifier is divided into two independent positive and negative power supplies for each stage, and six independent constant-voltage power -voltage 6-power supply system for controlling the influence between channels and stages.
The transformer uses a cut-core type, and the entire power supply section is designed to have low impedance.

The equalizer amplifier section uses a low-noise differential 2-stage / 3-stage direct-coupled active broad class A operation circuit. By applying a high voltage of ± 70 v, a large input resistance of 600 mv (RMS, 1 khz) is realized.
The Phono2 terminal allows switching between load resistance and capacity according to the cartridge.

Two output terminals are provided.
Out of these two systems, Output2 is capacitorless.

Lead relays are provided at the Rec out and Pre out terminals to eliminate noise when the power is turned on or off. The SY-77 uses an output short method to prevent sound quality degradation caused by signals passing through the relays.

The volume uses a 4-channel detent volume with 2 channels on one channel. By adjusting the volume before and after the flat amplifier, residual noise when the volume is reduced is suppressed.

Equipped with subsonic filter, mode switching, muting (with indicator).

A table of measured characteristics using the original computer system CADIS was attached to each unit to guarantee the characteristics and quality.

There was a carrying handle as an option sold separately.
By using this handle, it can be mounted on a JIS standard standard rack.

Model Rating
Type Control amplifier
Circuit system Equalizer amplifier : 2-stage and 3-stage differential direct-coupled active broad (Class A)
Flat Amplifier : 2-Stage Pure complimentary service Parallel Push-Pull (Class A)
Tone amplifier : 1-stage and 2-stage differential direct-coupled active broad
Input Sensitivity / Impedance Phono1 : 2.0mV/47k Ω
Phono2 : 2.0mV/47k Ω, 100k Ω / 20 pF, 240 pF
Tuner, Aux, Tape1/2 : 150mV/50k Ω
Output Voltage / Impedance
Tape Rec:
Output:
150mV/3.3k Ω
1.0V/600 Ω (50k Ω load, rating)
1.0V/600 Ω (50k Ω load, maximum)
Phono maximum allowable input 600mV RMS(1kHz)
Phono RIAA deviation 20 Hz to 20 kHz ± 0.2 dB
Harmonic distortion factor
Phono:


Aux:
0.012% (1 kHz at 1 V output)
0.004% (1 khz at 3 v output)
0.002% (1 khz at 10 v output)
0.003% (1 khz at 3 v output)
0.002% (1 khz at 10 v output)
Frequency characteristic Aux : 10 Hz to 100 kHz + 0 to 1.0 dB
S/N ratio (IHF-A network short) Phono:75dB
Aux:90dB
Tone control Bass : ± 10 dB (20 Hz), 2 dB step
Treble : ± 10 dB (50 kHz), 2 dB step
Subsonic filter 10 Hz, 12dB/oct.
Muting -26dB
Semiconductor used Transistor : 59
Diode : 42 pcs
AC outlet Switched : 2 systems, 400W
Unswitched : 1 line, 400W
Pwer 100 VAC, 50Hz/60Hz
Power consumption 26W
External dimensions Width 450x Height 93x Depth 379 mm
Weight 9.5kg
Sold Separately Carrying Handle TO-1 (2 Pieces 1 Set, ¥ 3,000)