What is stereo?

There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.

H.H. Scott '59

Sansui AU-3900 (1977)

Let's get right to the heart of hi-fi distortion. It hurts your ears. It hurts your music. And when you get right down to it, it's unnecessary! These amps have the stability, and more importantly, the circuit integrity, to eliminate practically all distortion. In the AU-3900 this translates to a power output rating of a continuous 22 watts per channel, min. RMS both channels driven, into 8 ohms from 40 to 20,000 Hz with no more than 0,15% THD. This is more than ample power for very clean musical reproduction from small to medium sized stereo speaker systems. And it's more than enough to give you pleasurable, ultra-low distortion sound at loud or soft listening levels.

Additional High-Quality Features
Tone Control - circuit is the CR type with click-stop rotary controls (10 positions each) for Bass and Treble.
High Filter - eliminates record surface noise, tape hiss, etc. without harming musical content.
Speaker Switch - lets you control two separate sets (A and B) of stereo speaker systems. It has four positions: OFF, A, B and A+B
Source Selectors - are the pushbutton type for easy selection of AUX, Tuner and Phono program source inputs.
Tape Monitor - switch also a button is provided.
Other Features - include a front-panel Headphone Jack, a Loudness switch to compensate for highs and lows during low-level listening, a Mode switch with mono and stereo positions, a Microphone mixing input. Two convenience AC Outlets (one "switched") and a large rear-panel ground peg.

Specifications AU-3900
Audio Section
Power Output (at rated distortion)
Music Power (IHF): 84 watts into 4 Ω at 1,000 Hz; 80 watts into 8 Ω at 1,000 Hz
Continuous RMS Power Both Channel Driven:
26 watts per channel into 4 Ω at 1 kHz
25 watts per channel into 8 Ω at 1 kHz
22 watts per channel into 8 Ω from 40 to 20, 000 Hz
Total Harmonic Distortion: less than 0,15% at rated power output
Intermodulation Distortion (70 Hz : 7,000 Hz = 4:1 SMPTE method): less than 0,2% at rated power output
Power bandwidth (IHF): 10 to 40,000 Hz at rated distortion
Load Impedance: 4 Ω to 16 Ω
Frequency Response (at 1 watt): 10 to 40,000 Hz, +0,5 dB -1,5 dB
RIAA Curve Deviation (Phono): 30 to 15,000 Hz; ±0,5 dB
Damping Factor: approx. 50 at 8 Ω load
Channel Separation (at rated output 1,000 Hz):
Phono: better than 60 dB
Aux, Tuner, Tape Monitor: better than 65 dB
Hum and Noise (IHF):
Phono: better than 75 dB
Microphone: better than 65 dB
Aux, Tuner, Tape Monitor: better than 90 dB
Input Sensitivity / Impedance (1,000 Hz for rated output):
Phono: 2,5 mV/ 50 kΩ
Microphone: 2,5 mV/ 10 kΩ
AUX, Tuner: 130 mV/ 50 kΩ
Tape Playback (PIN): 130 mV/ 50 kΩ
Max. Input Capability (at 1,000 Hz, 0.2% THD):
Phono: 200 mV/50 kΩ
Recording Output:
Tape (PIN): 100 mv
Bass: +12 dB -12 dB at 50 Hz
Treble: +12 dB -12 dB at 15 kHz
Loudness: 10 dB at 50 Hz; 8 dB at 10 kHz
Filters High: -3 dB at 7,000 Hz (6dB/oct.)
Muting (audio): 0 dB, -20 dB
AC Outles: switched Max. 100 watts unswitched total 150 watts
Semiconductors: 29 Transistors; 1 Zener Diode; 14 Diodes; 1 LED
Power Requirements: 100, 120, 220, 240 V 50/60 Hz
Power Consumption: 156 watts Max.; 60 watts rated
Dimensions (W x H x D): 400 x 120 x 240 mm (15¾" x 4¾x 9½")
Weight: 5,5 kg (13,2 lbs) net

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