Audio Database

AU-70
Commentary

A pre-main amplifier released as a full-fledged stereo amplifier.

7189 is adopted for the output tube, AB1It operates in P. P. (fixed bias system).
In this class, a multiple feedback circuit (total NF 26 dB) was introduced for the first time in Japan to reduce distortion over all bands.

A 3-stage amplifier circuit is used for the control amplifier section, and all circuits are contained in an NF loop to suppress noise and distortion.

Sansui's original 4-transistor head amplifier with transistor circuit index S = 4 and transistor noise index NF = 2 dB is used.

In the tone control circuit, the bass and treble sections are separated for each channel.
In addition, since it is equipped with tone defeat (tone circuit cancellation device), flat characteristics without waviness or loss of gain can be obtained.

Equipped with a blend circuit that can control the spread.
As you turn the knob to the right, you can freely adjust the sound spread from mono to stereo.

Equipped with center channel output terminal, 3-D stereo reproduction is possible.

Equipped with an output level meter that can be switched to 3 levels of 5W, 10W, and 15W.

Model Rating
Type Tube type pre-main amplifier
Power Amplifier Unit
Maximum power output 25W-25W
Harmonic distortion factor (20W) 0.15% or Less (1 kHz)
0.95% or Less (36 Hz)
Cross modulation distortion factor 0.85% or Less (15W, 50 Hz + 5 kHz)
Frequency characteristic 10 Hz to 80 kHz ± 1 dB or less
Output impedance 8 Ω, 16 Ω
Preamplifier Section
Gain at 20W output Phono(MAG):81dB/1.6mV
Phono(X-TAL):54dB/36mV
Tape:86dB/0.9mV
Mic:86dB/0.9mV
AUX(Tapemon):51dB/50mV
Tuner:51dB/50mV
Tone control CR Type
50 Hz : + 11 dB to -15dB
10 kHz : + 12 dB to -13dB
Equalizer NF Type
Tape(BTS)
Phono(RIAA)
<General>
Accessory circuit Presence control
Turnover : 150 Hz
Low Filter : 50 Hz, -12.5 dB
High Filter : 10 kHz, -13.5 dB
Loudness control
Tone defeat
Tape monitor
Headphone jack
Tape recorder recording / re-connector
Terminal for center channel amplifier
Level meter (3-step switching of 5W, 10W, 25W)
Blend control
Semiconductor used
Vacuum Tubes (9 pcs) 7189 : 4 pieces
6AN8 : 2
12AX7 : 3
Transistor (2SB-381) : 4
Germanium Diode (OA-81) : 2 Pieces
Silicon Diode (SD-1A) : 2 pieces
Selenium Rectifier (TC. 0.2P11/3) : 1 Piece
Pwer 100 VAC, 117 V, 240 V, 50Hz/60Hz
Power consumption 118VA
External dimensions Width 405x Height 142x Depth 320 mm
Weight 13.7kg