VICTOR/JVC JA-S77

Commentary

A pre-main amplifier with a tri-DC configuration in which all blocks of the equalizer, tone amplifier, and power amplifier are converted into DC.

The power amplifier section consists of a complete DC amplifier using a low-noise dual FET at the first stage.
In addition, class A and class B independent two power supply system is adopted. The double differential input stage with the common-phase feedback constant current circuit to the pre-drive stage is class A operation, and a constant voltage power supply is supplied from a transformer different from class B disconnection of the Darlington connection. Thus, stability of the midpoint potential is improved.

As the power amplifier section becomes DC, the preamplifier section is also DC.
The EQ circuit configuration consists of a first stage FET / ICL double differential input and a collector-follower pure complimentary service push-pull output. It is carefully designed with a DC drift compensation circuit and a latch-up prevention circuit to prevent abnormal operation when excessive input is applied.
The tone amplifier section also has a DC configuration of the first stage FET differential ICL, so that the frequency characteristics and the distortion factor hardly change regardless of the ON-Defeat of the tone control element.
In the FET differential ICL circuit, unlike bipolar transistors, the FET is originally a voltage amplifying element with a high input impedance. Therefore, the voltage can be directly amplified without being affected by the impedance of the equipment connected to the input.

The equalizer and and tone amplifier section use a pair FET that is connected so that FETs with good characteristics can be placed under the same temperature condition, and the minimum two coupling capacitors use capacitors with good sound quality that have been developed through more than 100 prototypes.

Equipped with 3-stage cartridge load switching function.

Equipped with a tape monitor switch with a luminous indicator.

Equipped with front recording and re-terminal.

The Phono input terminal is gold-plated.

Equipped with a pre-main separation switch with subsonic and DC switching.

Uses high-precision multi-contact volume with less distortion and sliding noise.

Equipped with a logarithmic compression type large power meter.

It is equipped with a highly sensitive 3 Oshige point protection circuit of independent detection type for left and right channels.

Model Rating

Type	Pre-main amplifier
Power Amplifier Unit
Circuit system	First stage dual FET double differential DC amplifier
Effective power (both channel operation, 20 Hz to 20 kHz)	82W + 82W (4 Ω, THD0.05%) 70W + 70W (8 Ω, THD0.02%)
Total harmonic distortion factor	0.02% or Less (8 Ω at Effective Output, 20 Hz to 20 kHz) 0.005%(1kHz)
Cross modulation distortion factor	0.01% or Less (8 Ω at Effective Output)
Frequency characteristic	DC ~ 100 kHz + 0 -1dB (Direct Input)
Signal-to-noise ratio	115 dB (IHF-A network, short circuit)
Preamplifier Section
Circuit system	All stages DC configuration, first stage FET differential ICL, class A operation
Input Sensitivity / Impedance	Phono : 2.5mV/37, 47, 100k Ω Tuner, Aux, Tape play : 200mV/50k Ω
RIAA deviation	20 Hz to 20 kHz ± 0.3 dB
Phono maximum allowable input	230 mv (RMS, 1 kHz)
Frequency Response (Aux)	3 Hz to 100 kHz + 0 -1dB
SN ratio (IHF-A short circuit)	Phono:81dB Aux:105dB
Power Supply Unit and Others
Circuit system	Class A and Class B independent 2 power source system
Rated power consumption (Electrical Appliance and Material Control Law)	182W
External dimensions	Width 450x Height 158x Depth 338 mm
Weight	11.5kg
Sold Separately	Rack Handle BH-W150 (¥ 4,000)