Audio Database

SU-30A
Commentary

This tube type preamplifier was developed using Technics technology.
The model number has been changed 3 times : EAA-2008, SU-2008 and SU-30A.

A ripple filter using a transistor is incorporated in the rectifier circuit of the heater to minimize hum noise by igniting with DC without ripple, and noise level is reduced by shielding the power supply and adopting low noise resistance.

The equalizer circuit consists of 3-stage NF type, and the buffer amplifier consists of SRPP (Shunt Regulated Push Pull) type cathode follower circuit.

In order to improve the accuracy of the playback characteristics of the equalizer circuit and to avoid unnecessary coloring, we use capacitors and resistors with precision within ± 1% error. In addition, the deviation from the RIAA curve is kept within ± 0.3 dB by measuring and adjusting each unit when it is assembled.

The volume employs a special 4-series volume that adjusts the output of the tone amplifier simultaneously, reducing residual noise.

The tone control circuit adopts Technics original system using special double volume.
In this method, when one side is in contact with the resistor, the other side is in contact with the silver conductor so that only one capacitor is inserted. Also, at the midpoint, both brushes are on the silver conductor so that flat characteristics can be obtained.

Model Rating
Type Tube type preamplifier
Input Sensitivity / Impedance Phono1, 2 : 1.2mV/47k Ω
Tuner1, 2 : 70mV/150k Ω
AUX1 : 0 ~ 70 mV Adjustable / 70k Ω
AUX2 : 70mV/150k Ω
Tape Head 9.5 cm, 19 cm : 1.6mV/470k Ω
MIC : 1.4mV/47k Ω
Maximum allowable input
(1 kHz, 0.1% distortion rate)		 Phono1, 2 : 400 mV
Tuner1, 2 : 50 v
AUX1, 2 : 50 V
Tape Head 9.5 cm, 19 cm : 500 mv
MIC:400mV
Tape monitor
(at rated output)		 Rec out : 70mV/500 Ω
Playback : 70mV/150k Ω
Rec/Play (DIN) : 70mV/90k Ω, 150k Ω
Output Level / Impedance 15V/500 Ω (Maximum Output)
Signal-to-noise ratio (IHF, A-network)
Input short Input Open
Phono1, 2 : 64 dB or more 58 dB or more
Tuner1, 2 : 75 dB or more 70 dB or more
AUX1, 2 : 75 dB or more 70 dB or more
Tape Head 9.5cm: 63 dB or more 50 dB or more
19cm: 63 dB or more 51 dB or more
MIC: 63 dB or more 55 dB or more
Total harmonic distortion rate (1 kHz) Not more than 0.1%
Frequency characteristic Phono1 and 2 : within ± 0.3 dB deviation from RIAA standard curve
Tuner1, 2 : 5 Hz to 50 kHz, ± 0.5 dB
AUX1, 2 : 5 Hz to 50 kHz, ± 0.5 dB
Tape Head 9.5cm:
19cm:		 NAB Deviation from 9.5 cm curve + / - 0.5 dB (adjustable)
Deviation from NAB curve 19 cm + / - 0.5 dB
MIC : 10 Hz to 50 kHz, + 0 -1dB
Semiconductor used
Vacuum tube : 12AX7 : 8
6X4 : 1 Piece
Transistor : 2SB126 : 1
Diode : SW-1-01 : 4
Pwer 100 VAC, 50/60Hz
Power consumption 35VA
External dimensions Width 420x Height 150x Depth 250 mm
Weight 7.6kg