An amplifier and AM/FM tuner (AKA Stereo Receiver, hence the name) from 1977, available with a black or chrome front and made for two to four loudspeakers, one pair at 4 - 16 ohm/speaker or two pairs at 8 - 16 ohm/speaker.
The effect/channel is 2 x 110 W at 4 ohm or 2 x 95 W at 8 ohm according to DIN. The effect according to FTC is 2 x 95 W at 4 ohm and 2 x 90 W at 8 ohm in the range of 40-16,000 Hz; 2 x 90 W or 2 x 85 W at 4 or 8 ohm respectively for the range of 20-20,000 Hz. It reaches down to 10 Hz and up to 50 kHz at a distortion level of 1%.
The amplifier has an electronic protection circuit to protect its transistors and connected speakers. Its effect is boosted by having double direct current sources. The equalizer uses what was then a newly developed Hitachi integrated circuit for stability and dynamics.
The FM tuner has a two-way MOSFET and four variable capacitors, setting the DIN sensitivity to 1.2 μV (75 Ω) in stereo. Other values are improved by using a four-step differential amplification, ICs, and three ceramic filters. For both AM and FM, releasing the nice, big, ball bearing supported tuner knob triggers a fancy Automatic Frequency-locking Circuit (AFC) that stabilizes the frequency. The AM tuner also uses ICs and one ceramic filter.
On the front panel: Power switch*, 3.5 mm ø headphone jack, speakers A on/off*, speakers B on/off*, tone controllers: bass**, midrange**, treble**, lowpass filter on/off*, highpass filter on/off *, volume** and balance**, Tape copy selector (1 to 2, none, 2 to 1)***, Tape monitor selector (1, none, 2)***, Function selector (AM, FM, FM Mute Auto Lock, Phono, Aux)**, Tuning**, Stereo/Mono*, Loudness filter*, Adaptor*. The backlit panel of indicator needles and lights show signal level, FM tuning, stereo on/off, FM mute auto lock (to silence noise between stations) on/off, AM, FM, Phono, Aux mode indicators, and an FM/AM frequency indicator needle.
*) Two-position "Radio button"
**) Knob
***) Three-position flip switch
On the back: 4 300 ohm and 75 ohm ins for FM antenna, AM in, earth wire connector for turntable, antenna, phono in L/R, aux in L/R, tape 1 in L/R, tape 1 rec out, tape 1 rec/play connector, tape 2 in L/R, tape 2 rec out, DolbyTM NR adaptor in L/R, DolbyTM NR adaptor out L/R, Speakers A and B (+/- L and +/- R), main fuse for voltage change-over, power cord.
SR-903 is 49 cm wide, 14.4 cm tall, 40 cm deep, and weighs in at 13.5 kg.
The noder is a happy owner of one of these, still in top notch condition, with the exception of a slight tendency of the function selector to cause some level of noise in the output. It is a powerful, rigid piece, that produces a rich, genuine, and dynamic sound.