This Pioneer SX-636 was a mid-range offering from Pioneer in 1974 and retailed for $350.00. It only produces 25 watts per channel into 8 ohms but, as Pioneer stated in their marketing brochure:
“Not all high fidelity situations require high powered equipment. If your listening room is of average size, and what you really want is more efficiency and more sophisticated versatility in a medium-powered model, Pioneer’s new SX-636 will be a good choice.”
The SX-636 came out a few years before the wattage wars so 25 wpc didn’t seem inadequate. And it wasn’t for most listening situations. Besides, the receiver looks good and has a number of features that lower end receivers don’t have.
The front panel has bass and treble controls, high filter, mono and loudness switches, and a function control for FM, AM, PHONO, MIC and AUX. The blackout style, FM-linear dial scale has two tuning meters, illuminated program indicators, and a stereo headphone jack. The control switches are push button instead of the toggle style you see on many of the later model Pioneers. The illuminated dial pointer is a nice touch as well.
- Tuning range: FM, MW
- Power output: 25 watts per channel into 8Ω (stereo)
- Frequency response: 20Hz to 30kHz
- Total harmonic distortion: 0.5%
- Damping factor: 35
- Input sensitivity: 7mV (mic), 2.5mV (MM), 150mV (DIN), 150mV (line)
- Signal to noise ratio: 65dB (mic), 70dB (MM), 90dB (line)
- Output: 150mV (line), 30mV (DIN)
- Speaker load impedance: 4Ω (minimum)
- Semiconductors: 1 x FET, 3 x IC, 33 x transistors, 17 x diodes
- Dimensions: 480 x 147 x 405mm
- Weight: 11.2kg
- Year: 1974
The cabinet is wood grain vinyl and doesn’t look too bad.
The Pioneer SX-636 has a good tuner section and a very good phono section. The FM tuner utilizes a low-noise FET and a 3-gang variable capacitor in the front end. High fidelity sound reproduction is achieved with a precise phono equalizer that keeps RIAA deviation within +- 0.5dB.
As mentioned above, the direct-coupled OCL power amplifier provides continuous power output of 25 watts per channel at 8 ohms from 20 Hertz to 20,000 Hertz with no more than 0.5% total harmonic distortion.
The SX-636 does have some occasional issues with bad transistors (especially the 2SC1451 transistors on the power amp) and, of course, burnt out lamps. It also does not have a protection relay, and instead, relies upon two fuses on the back panel. But, these are more for the protection of speakers rather than the amp itself.
The build quality of the mid 1970’s Pioneers stereos was very good. The later SX-X50 series was probably the best but the SX-X3X series is a close second and doesn’t have too many difficult to find proprietary IC’s. It is also very easy to work on which can save you money if you need to have a tech look at it.
Overall, Pioneer’s SX-636 is a great mid-range receiver. If you’re looking for something with a good phono amp to play records or have a small to medium sized room you want to fill with great sounding music then be sure to check out the SX-636.