The QR-6500 has three main features; 4-channel QS synthesizer and decoder, 4-channel 280-watt integrated amplifier and super-sensitive stereo FM/AM tuner. Basically, Sansui took what they developed in the earlier QR-6500 and improved it.

At the time, their new QS regular matrix system with vario-matrix circuitry was the most advanced method of reproducing a sound field in 4-channel mode. The QS synthesizer can transform a regular 2-channel signal into a rich 4-channel output. This meant that the user's 2-channel stereo recordings were still available on the quad receiver, and quadraphonic recordings were not mandatory. Nevertheless, to take full advantage of the QR-6500, it was recommended to use 4-channel recordings with QS encoding.

The regular QS matrix decoder can decode any four-channel QS encoded signal. This would work with any encoded recordings, tapes, and even FM broadcasts.

Technical data:

Tuning range: FM/AM

Power Output: 33W/Ch into 8Ω (Quadraphonic)

Frequency response: 30Hz to 30kHz

Total Harmonic Distortion: 0.5%

Damping factor: 30

Signal to Noise Ratio: 70dB (line)

Channel separation: 45dB (line)

Speaker load impedance: 4Ω to 16Ω

Dimensions: 536 x 181 x 362 mm - 21 3/16 x 7 3/16 x 14 5/16 inches

Weight: 22 kg - 48.5 lbs

As mentioned above, the tuner in the QR-6500 is excellent. It uses three dual-gate MOS FET transistors and a precision quadruple variable capacitor. Visually, it has an illuminated dial gauge and meters for both signal strength and tuning.

Sansui 4-channel synthesizer/decoder control, a five-position rotary knob located on the right side of the front panel, allows you to select two different QS synthesizer modes (Surround and Hall), two regular QS matrix modes (Surround and Hall) and an additional Phase Matrix mode for decoding of SQ recordings.

The QR-6500 is not intended to be a feint of the heart when it comes to repair or restoration. The 4-channel layout is complicated and makes the interior crowded. Keep that in mind if you find it. It will most likely require maintenance or repair, which can become expensive quite quickly depending on what needs to be done.

Take a look at all the speaker outputs on the rear panel! Up to five sets of speakers can be connected to the QR-6500. There are also an incredible number of inputs for both 2-channel and 4-channel sources. There's even a de-emphasis switch - a holdover from the days when radio broadcasters intended to broadcast with Dolby noise reduction. Not so useful today. There are also three AC outlets on the rear panel, one of which is controlled by a switch on the front panel.

The Sansui QR-6500 is a beautiful quadraphonic receiver that has a solid place in the history of quadraphonics. However, if you don't want to mess around with 4-channel audio, you may be better off sticking with one of Sansui's 2-channel offerings. If you want to play quad source material, you can also look at the later Sansui QR-X001 series which is excellent

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