Audio Database


A control amplifier with low distortion by class-A operation in all stages.

In order to completely remove switching distortion and crossover distortion, all stages are operated as class A.
As a result, the rated distortion factor of 0.003% is achieved at 20 Hz to 20 kHz and 1 V output from the Phono MM to the output terminal.

A low-noise dual FET is used for MM, and newly developed low-noise transistors M67L and M68L are used for MC preamp, resulting in high S / N ratio.

The SU-A2 employs a DC amplifier configuration that eliminates the interstage capacitor of the signal system and the capacitor with a time constant in the NFB loop. As a result, the amplifier has a DC gain and eliminates the phase loop, improving the fidelity of waveform transmission.
Moreover, the coupling capacitor is removed from the phono equalizer to form a DC equalizer.

In order to suppress DC drift, which is the most important point of DC amplifier, an active thermal servo amplifier with thermal feedback is adopted.

For switching the input selector and the recording mode selector, a touch switch method is adopted in which a high-reliability relay for small signals is operated by a micro switch. This prevents signal wiring from being routed.
The use of a fade circuit eliminates shock noise caused by switching between input and output.

Equipped with a Universal Frequency Equalizer (UFE) consisting of 8 elements, 4 elements each on the left and right sides. The two elements inside the equalizer can also be used as butterfly tone controls.
In addition to the UFE, the sound field can be corrected by using the built-in sine wave, square wave, pink noise, wobble tone oscillation switch, microphone circuit and high-resolution meter.

Equipped with 3 types of switchable meters : peak / peak hold / average.

Equipped with a microphone terminal that enables input impedance switching and microphone level adjustment.

Equipped with a variable type loudness control that conforms to the Fletcher Munson curve.

A large toroidal transformer with low DC resistance is used for the power supply.

For the volume, a 6-channel conductive plastic 10 channel volume is used for sound.

Phono1 and 2 Equipped with independent input sensitivity, input resistance and capacitance selector.

It is equipped with a headphone amplifier that can control the level.

Model Rating
Type Stereo DC control amplifier
Input Sensitivity / Impedance Phono1, 2 mm : 2.5mV/22k, 33k, 47k, 75k, 100k Ω
/ 100p, 150p, 200p, 300p, 500 pf
Phono1, 2 mc : 100 μ V/10, 22, 47, 100, 220 Ω
Tuner, Aux1, Tape : 150mV/47k Ω
Mic : 2mV/600 Ω
Maximum Allowable Input (1 kHz, RMS) Phono MM:500mV
Phono MC:20mV
Total harmonic distortion rate (20 Hz to 20 kHz) Tuner, Aux, Tape, Phono MM : 0.003% (VRmax, 10 voutput)
0.003% (VR-30dB, 1 Voutput)
Phono MC, Mic : 0.005% (VRmax, 10 Voutput)
0.005% (VR-30dB, 1 Voutput)
Signal-to-noise ratio (IHF-A) Phono MM : 95 dB (2.5 mV input)
107 dB (10 mV input)
Phono MC : 80 dB (100 μ V input, input equivalent noise voltage : -160dBV)
Frequency characteristic Phono MM : DC ~ 20 kHz, RIAA ± 0.2 dB
Phono MC : 30 Hz to 20 kHz, RIAA ± 0.2 dB
Tuner, Aux, Tape : DC ~ 20 khz + 0 -0.2 db
Mic : 20 Hz to 20 kHz + 0 -1dB
Universal tone equalizer characteristics
(Level : Left / Right Independent Variable)
15 Hz to 60 Hz to 240 Hz (center frequency) : ± 10 dB (Q = 0.7 to 7.0)
63 Hz to 250 Hz to 1 kHz (center frequency) ± 10 dB (Q = 0.7 to 7.0)
(turnover frequency) : + / - 10 dB (Selectable)
250 Hz to 1 kHz to 4 kHz (center frequency) : ± 10 dB (Q = 0.7 to 7.0)
(turnover frequency) : + / - 10 dB (Selectable)
1 kHz to 4 kHz to 16 kHz (center frequency) : ± 10 db (Q = 0.7 to 7.0)
Filter characteristic Equalizer subsonic fileter : 30 Hz, -12dB/oct
High fileter : 8 kHz, 12 kHz, -18dB/oct.
Low fileter : 15 Hz, 30 Hz, -18dB/oct.
Oscillator characteristic Sine wav, Square wave : 20 hz to 20 khz (continuously variable)
Warble tone : 20 Hz to 20 kHz (continuously variable)
Pink noise : modulation degree ± 7%
Output Level / Impedance Rec out : 150mV/500 Ω
Pre-out (front, rear) : rated 1V/500 Ω, maximum 10V/500 Ω
Meter characteristic Indication Range : -50dB to + 10 dB (Regular Interval Scale)
Frequency characteristics (indication accuracy) : 10 Hz to 20 kHz ± 1 dB (at + 10 dB to -40dB indication)
10 Hz to 10 kHz ± 3 dB (with less than -40dB indication)
Attenuator : -20dB to + 10 dB (continuously variable)
Peak indication attack time : 50 μ sec
Recovery time : 750 msec (0 dB → -20dB)
Peak hold indication attack time : 50 μ sec
Peak hold indication recovery time : 2 hours (0 dB → -3dB)
Average indication attack time : 330 msec
Average indication recovery time : 250 msec (0 dB → -20dB)
Muting -20dB, off
Fade circuit characteristics Fade-out, fade-in time constant : 150 msec
Pwer 100 VAC, 50Hz/60Hz
Power consumption 240W
External dimensions Width 450x Height 205x Depth 574 mm
Weight 38.5kg