Sony STR-7055

The Sony STR-7055 was made from 1972 until 1976. It has a clean and classic styling and looks especially good with the wood case. It was near top of the line with only the STR-7065 above it. It produces 55 watts per channel into 4 ohm loads and 35 wpc into 8 ohm loads..

The STR-7055 boasts an elegantly designed satin-finish panel and knobs. It features a highly efficient medium-power amplifier with versatile control options.

The STR-7055’s front panel showcases a prominent dial cut-out surrounded by green-lit scales and a meter face. Adjacent to it are two large knobs for tuning and volume adjustment. The balance control, which is located below the volume knob, can be operated using a small lever. The FM dial scale has linear calibrations, with a red STEREO indication appearing on the right during stereo reception. The tuning meter serves as a zero-center indicator for FM and displays relative signal strength for AM.

This receiver allows you to connect and activate three pairs of speakers, either individually or in two combinations of two pairs, using a selector knob. Furthermore, there is an OFF position on the selector for private listening through headphones, utilizing a front-panel jack.

For audio customization, there are separate bass and treble tone controls for both channels. These controls are concentric and equipped with slip-clutch knobs for smooth operation. Additionally, a single knob operates the high and low cut filters, allowing you to connect either filter, both, or neither.

The receiver offers various operating modes, including stereo with normal or reversed channel positioning. You can also choose to listen to either input channel separately or their combined sum (mono) through both speakers. In the latter mode (L + R), the FM multiplex circuits are automatically deactivated.

The FUNCTION control lets you select signal sources such as PHONO, FM, AM, or Aux. It also provides two tape copying positions for duplicating recordings between two tape recorders. Moreover, two separate TAPE MONITOR lever switches enable playback or monitoring from either recorder while recording or copying tapes.

It really looks nice when lit up as well.

Here are some of the features of the STR-7055:

• Tape monitoring for two recorders
• Three-way speaker selector switch
• Direct-coupled power output circuits
• Separate tone controls for each channel
• Center-of-channel precision tuning meter
• Accepts any four-channel decoder
• Preamp-out/Amp-in connection for added flexibility
• Single control high-and-low frequency filters
• FM interstation muting circuitry
• Oiled-walnut cabinetry included at no extra cost

Here is what the flyer for the Sony STR7055 said about it at the time:

The STR-7055 FM front-end includes newly developed junction FET’s in its mixer and RF stages, providing high sensitivity (2.0 nV, IHF) while retaining the ability to handle strong local stations without overload, cross-modulation or spurious responses.

The IF section has permanently aligned solid-state filters and a high-gain IC amplifier/ limiter for excellent selectivity (70 dB, IHF) and a superb capture ratio of 1.0 dB—a multipurpose IC multiplex stereo section reduces distortion to 0.5% in stereo and 0.2% in mono, both measured at full modulation. An effective muting circuit silences all interstation noise when tuning from station to station, while the center-of-channel tuning meter and the long, linear dial scale insure precision tuning.

AM Section

Engineered for maximum realizable fidelity, the AM tuner section of the STR-7055 employs triple-tuned solid-state filters and a new IC with an automatic gain control (AGC) circuit to maintain high sensitivity, minimum distortion and superb signal-to-noise ratios.

Preamplifier And Control Sections

The preamplifier section of the STR-7055 includes a high-reliability IC to insure long-term stability, accurate equalization and extremely high signal-to-noise ratios in low-level phono signal service. Dual friction-clutch bass and treble controls, multiple filter settings and loudness compensation extend the versatility of this receiver to that approaching professional studio components. Two pairs of inputs and outputs for tape recorders permit making two recordings simultaneously as well as tape duplication. Any SQ or other four-channel matrix decoder easily plugs into the STR-7055 in seconds. For all its control versatility, careful attention to convenience of operation and “human engineering’ enable you to quickly master the many front panel features.

Power Amplifier Section

Capable of delivering continuous power output of 35 watts per channel at all frequencies from 20 Hz to 20,000 Hz, with both channels driving 8-ohm loads, the power amplifier section uses stabilizing differential amplifier input circuitry and balanced negative and positive power supplies. The resulting direct-coupled output circuitry has wide-band response, minimal phase shift at critical low frequencies and a high damping factor (50 at 8 ohms) for distortion-free powerful performance throughout the audio range. Continuous power into 8-ohm loads at 1 kHz with both channels driven Is 45 watts per channel at less than 0.2% total harmonic or intermodulation distortion. As many as three pairs of
speaker systems can be connected to the STR-7055 and convenient front-panel switching lets you select any one or two pairs for multiple-room stereo.

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There was also an STR-7055A model that was made later in the production run around 1976-1978. No one really seems to know the difference between the two models.

As you can see it has large heatsinks that protrude out the back of the receiver.  It also has connections for three sets of speakers.

After testing the Sony STR-7055, Hi-Fi Stereo Review said:

The overall performance of the Sony STR-7055 left nothing to be desired, and our positive reaction to the receiver was enhanced by the smoothness of its controls, its noncritical tuning, and its noise – free FM muting system.

Overall the STR-7055 is a very good receiver. Sony made quite a few of them so they are somewhat common so parts are readily available. The vintage Sony look is very appealing, and the performance is excellent, so it is a receiver worth acquiring if you get the chance.