An FM/AM stereo receiver that improves on its predecessor, with advanced filtering and low-distortion audio circuitry.
Overview
The amplifier uses a quasi complementary SEPPP OTL circuit design, and the tuner section was advanced for its time. FM input is a 300 Ω balanced antenna, and AM uses a built-in bar antenna. It was engineered for strong reception and low interference. A feeder antenna comes with it. The unit weighs 9kg and measures 434mm wide, 145mm high, and 348mm deep.
Specifications
| Circuit system | Quasi complementary service SEPPP OTL circuit |
| FM Tuner Section Antenna terminal | 300 Ω equilibrium |
| FM Tuner Section Sensitivity | 2.2 μv (IHF) 1.7 μV (S/N : 30 dB) |
| FM Tuner Section Image interference ratio | 55dB |
| FM Tuner Section IF interference ratio | 90dB |
| FM Tuner Section Spurious interference ratio | 78dB |
| FM Tuner Section AM suppression ratio | 55dB |
| FM Tuner Section Capture ratio | 1.5dB |
| FM Tuner Section Selectivity | 60dB(IHF) |
| FM Tuner Section Signal-to-noise ratio | 68dB |
| FM Tuner Section Frequency characteristic | 30 Hz to 15 kHz, + 0 -2dB |
| FM Tuner Section Distortion Factor (400 Hz, 100% Modulation) | mono:0.3% stereo:0.8% |
| FM Tuner Section FM stereo separation | 35 dB or More (1 kHz) |
| AM Tuner Section Antenna terminal | Built-in bar antenna With External Antenna Terminal |
| AM Tuner Section Sensitivity | Bar antenna : 48dB/m External antenna : 30 μV |
| AM Tuner Section Image interference ratio | 56dB(1000kHz) |
| AM Tuner Section IF interference ratio | 40dB(1000kHz) |
| AM Tuner Section Signal-to-noise ratio | 50dB |
| AM Tuner Section Distortion factor | 0.8% |
| Amplifier Unit Output Dynamic Power (IHF) | 65W (8 Ω) 80W (4 Ω) |
| Amplifier Unit Effective output (1 kHz, half-channel) | 25/25W (8 Ω) 30/30W (4 Ω) |
| Amplifier Unit Effective output (1 kHz, both channels) | 22W + 22W (8 Ω) 25W + 25W (4 Ω) |
| Amplifier Unit Effective output (20 Hz to 20 kHz, both channels) | 20W + 20W (8 Ω) |
| Output Level / Impedance Recording Terminal | 250mV/10k Ω |
| Output Level / Impedance [REC/PB] Output | 30mV/82k Ω |
| Output Level / Impedance Headphone Output | 8 Ω ~ 10k Ω |
| Output Level / Impedance Speaker terminal | 4 Ω ~ 16 Ω |
| Preamplifier / power amplifier terminal Preamplifier output | 0.5V/5k Ω |
| Preamplifier / power amplifier terminal Power Amplifier Input | 0.5V/50k Ω |
| Harmonic distortion factor | 0.8% or Less (Rated Output) 0.1% or Less (at 1W Output) |
| Cross modulation distortion factor (60Hz:7kHz=4:1) | 0.8% or Less (Rated Output) 0.1% or Less (at 1W Output) |
| Frequency characteristic Phono RIAA standard Aux, Tape, Rec/PB (input) | 20 Hz ~ 40 kHz + 0 -3dB |
| Input Level / Impedance (at rated output) Phono Terminal | 2.5mV/47k Ω |
| Input Level / Impedance (at rated output) Mic Terminal | 2.0mV/47k Ω |
| Input Level / Impedance (at rated output) AUX Terminal | 250mV/100k Ω |
| Input Level / Impedance (at rated output) Tape Terminal | 250mV/100k Ω |
| Input Level / Impedance (at rated output) [REC/PB] Input | 250mV/100k Ω |
| Signal-to-noise ratio Phono Terminal | 60 dB |
| Signal-to-noise ratio AUX terminal | 70 dB |
| Signal-to-noise ratio Tape Terminal | 80 dB |
| Signal-to-noise ratio [REC/PB] input | 80 dB |
| Signal-to-noise ratio Mic Terminal | 60 dB |
| Damping factor | 25 (8 Ω) |
| Tone control Treble | 10 kHz, ± 10 dB |
| Tone control Bass | 100 Hz, ± 10 dB |
| High filter | 6dB/oct, 5 kHz or more |
| Loudness switch (at -30dB) | 50 Hz, + 6 dB 10 kHz, + 4 dB |
| Semiconductor used | Transistor : 32 IC:2 FET:2 Diode : 22 |
| Power | 100 VAC, 50Hz/60Hz |
| Power outlet | 300W, non-interlocked : 1 system |
| Power consumption | 63W |
| External dimensions | Width 434x Height 145x Depth 348 mm |
| Weight | 9kg |
| Attachment | Feeder antenna |
| Fuse | 2Ax2 |
Design
The amplifier section uses a high-power IC developed especially for audio. Two power supplies feed it through a direct coupling method, which gives low distortion at high output. The tuner front end uses a newly developed junction FET, and the IF section has a 2-element 1-package solid-state filter. The FM multiplex circuit has a coil unit for better stereo separation and lower distortion. The AM tuner uses a triple chain IFT with a solid-state filter. Tone control is NF-type, the volume control is balanced, and a speaker selector switch handles two sets of speakers. The preamp and main amp can be used separately, so the receiver can work in a multi-amplifier system. It also has pure electronic stereo, automatic monaural switching, a stereo display lamp, and a function-linked dial display.
Context
The Sony STR-6550A was a model update from the STR-6550. It offered better overall performance and stayed easy to use as a stereo receiver.
Similar items on eBay
No exact Sony STR 6550A listings are live right now — these searches show current Sony and similar vintage audio gear on eBay:
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.
Related Models
- Sony STR-DH190
- Sony SQR-6650
- Sony STR-6040
- Sony STR-6060
- Sony STR-6120
- Marantz 2226 (1974-1976)
- Marantz 2226B (1979-1980)
- Marantz 2235 (1974-1977)
- Marantz 2238B (1978-1980)
- Marantz 2250B (1978-1980)