ADC 404-S (1970)
The ADC 404-S is a compact receiver. It was the first receiver Audio Dynamics Corporation ever made, and it is a very uncommon unit. It arrived late. The 404-S was not widely available until near the end of 1970, and by then ADC was entering a crowded market already full of integrated receivers from bigger names.
It was priced at $219.95 complete, including a walnut cabinet and dust cover.
The amplifier section was rated at 60 watts IHF into 4 ohms (both channels driven), and delivered 35 watts per channel into 8 ohms. It used all-silicon transistors throughout - no ICs - on glass-epoxy printed circuit boards with plug-in transistors meant to simplify servicing. The FM tuner measured well: sensitivity of 2.1 µV (IHF), with stereo separation of 32 dB at 100 Hz, 30 dB at 1 kHz, and 20 dB at 10 kHz. Total harmonic distortion was moderate at 0.7% at 1 kHz and 0.5% at 400 Hz at 5 watts output. That is not exceptionally low, but it was acceptable for the era.
The front panel has two microphone jacks and two headphone jacks, plus a four-position input selector (Tuner, Phono 1, Phono 2, Aux). On the rear are two pairs of speaker connectors (4-16 ohms). The mic inputs and monitoring features suggest ADC aimed the 404-S partly at semi-professional recording use as well as home hi-fi.
Not everything was smooth. Audio noted a noisy audio preamp on a pre-production unit, and said the FM muting circuit could be temperamental. Dimensions are 5¼ × 17¾ × 11½ inches, weight 18 lbs, power draw 75 watts.
The 404-S remains obscure. Few were sold, and fewer survive. No production run dates, no service manual, and no frequency response or S/N ratio figures have turned up in the record. What exists is a single thorough review.
Known Specifications (from Audio, April 1970)
- Output: 60 W IHF at 4 ohms (both channels driven); 35 W per channel at 8 ohms
- FM sensitivity: 2.1 µV (IHF)
- Stereo separation: 32 dB at 100 Hz, 30 dB at 1 kHz, 20 dB at 10 kHz
- THD: 0.7% at 1 kHz, 0.5% at 400 Hz (5 W output)
- Inputs: Tuner, Phono 1, Phono 2, Aux
- Front panel jacks: 2 mic, 2 headphone
- Speaker outputs: two pair, 4–16 ohms
- Dimensions: 5¼ × 17¾ × 11½ inches
- Weight: 18 lbs
- Power: 105–120 V, 50–60 Hz, 75 W
- Construction: all-silicon transistors, no ICs; glass-epoxy PC boards; plug-in transistors
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