Sansui QA 7000

Four amplifiers in one chassis. A rear-panel switch bridges them into a stereo brute. That was the most practical sales pitch quadraphony had.

Overview

Pick up a QA-7000 and the first thing you notice is the weight, most of it transformer and heatsink. Sansui's own manual describes the power supply as a "jumbo power transformer" paired with two oversized 10,000µF capacitors in a plus/minus dual-supply arrangement, feeding four separate all-stage direct-coupled OCL pure complementary amplifiers. The topology matters more than the marketing language: direct coupling eliminates capacitors from the signal path, the first-stage differential amplifier keeps DC offset in check, and the claimed damping factor of approximately 100 into an 8-ohm load suggests genuinely firm cone control for a quadraphonic integrated. Crossover distortion, the manual notes, is "effectively eliminated."

The numbers underneath that architecture are where the QA-7000 gets interesting — and where its selling proposition lives. In four-channel use, continuous RMS output is 20W per channel into 8 ohms with each channel driven at 1kHz. That is not a lot of power by 1973 standards, and four-channel amplifiers were routinely criticized for exactly this shortfall. Sansui's answer was the BTL switch on the rear panel. Bridging each front/rear amplifier pair converts the QA-7000 into a 2-channel stereo amplifier rated at 50W per channel into 8 ohms — more than double the per-channel figure — or alternatively into a 4-channel front-channel or rear-channel amplifier at the same 50W × 2, to be paired with a separate stereo amp for the remaining pair. Four channels driven simultaneously at 1kHz yields 15W × 4 into 8 ohms; across the full 20Hz–20kHz band, that figure settles to 12W × 4. Music power (IHF) at 1kHz is quoted at 88W into 8 ohms and 108W into 4 ohms, with BTL operation reaching 144W and 166W respectively. Read those last numbers with the usual IHF skepticism — they are short-term peaks, not continuous ratings — but the continuous figures are honest enough.

Distortion is specified conservatively: total harmonic distortion below 0.05% for the preamplifier section alone, below 0.1% for the power amplifier at rated output, and below 0.3% in BTL mode. Intermodulation distortion (SMPTE, 70Hz:7kHz at 4:1) is under 0.15% in normal operation and under 0.5% bridged. Power bandwidth (IHF) spans 10Hz to 30kHz, frequency response from the AUX input is 20Hz–40,000Hz (+1dB, −2dB), and the power amplifier alone manages 10Hz–50,000Hz within ±1dB at 1W. The phono stage — a three-stage PNP-NPN-PNP direct-coupled equalizer drawing 44V from a constant-voltage supply — tracks the RIAA curve within ±0.5dB from 30Hz to 15,000Hz and will accept up to 270mV RMS before clipping, roughly 40dB of headroom above the 2.5mV nominal sensitivity. Hum and noise figures are 70dB or better on phono, 80dB or better on the four-channel sources, and 90dB or better for the power amplifier alone.

The control surface is where the QA-7000 separates itself from the pack of half-hearted quad receivers. There are four large illuminated VU meters across the front — two of them go dark in 2-channel mode — plus a master input level-set control that adjusts sensitivity across all sources simultaneously. Tone controls are split: separate bass and treble for front and rear channels, each offering ±15dB at 50Hz and 15kHz. Front and rear left/right balance controls are friction-coupled and independent. A four-channel loudness contour adds +8dB at 50Hz and +3dB at 10kHz with the volume at −30dB. Two stereo headphone jacks sit on the front panel, one for the front pair and one for the rear — a genuinely rare feature that let owners audition quad mixes privately without disturbing the household.

The function selector covers seven positions, and this is the heart of Sansui's QS system. In addition to straight 2-channel stereo and discrete four-channel pass-through, the QA-7000 decodes QS Regular Matrix in both "Hall" and "Surround" variants, decodes CBS SQ-encoded discs via the Phase Matrix circuit, and synthesizes four channels from any two-channel source through the QS Synthesizer — again in Hall or Surround flavors. The QS Vario-Matrix circuit was claimed to bring inter-channel separation to a level comparable with discrete four-channel tape. The built-in 2-4 Synthesizer Encoder goes one step further: it lets owners convert a stereo source to four channels in real time and route the result to the four-channel tape outputs, turning the amplifier into a quadraphonic recording hub. Two complete four-channel tape loops are provided alongside a separate two-channel tape monitor, and the preamplifier and power amplifier sections can be separated instantly for insertion of external processors.

Input and output facilities are extensive even by the standards of the era: two phono inputs, two four-channel AUX inputs, one four-channel tuner input, two four-channel tape decks, and one two-channel tape deck, all on the rear panel. Tape-to-tape dubbing works in either 2- or 4-channel, and any source can be recorded to either or both decks simultaneously. The preamp output is rated at 800mV into 600 ohms with a maximum of 6.5V before 0.5% THD. The output stage uses an emitter-follower circuit with low output impedance, and a relay-equipped transient canceller suppresses the power-on pop that plagues most solid-state gear of the period. A protection circuit guards both speakers and output transistors, backed by what the manual calls "super-jumbo" heatsinks.

Semiconductor count is 97 transistors, 2 FETs, 62 diodes, and 2 Zener diodes. Power requirements cover 100/117/220/240V at 50/60Hz with 50VA switched consumption. The matching tuner was the Sansui TU-7500, designed to sit beside or stack with the QA-7000 to form a complete four-channel control center.

Contemporary coverage of the QA-7000 was thin but real. HiFi-Stereo (1974, p.22) ran new-product coverage placing the QA-7000 alongside announcements from McKay Dymek and other four-channel specialists. The same publication's new-products column in August 1974 (p.22) ran alongside announcements from McKay Dymek and other four-channel specialists, placing the QA-7000 squarely in the mid-decade quadraphonic push. It is worth remembering that quadraphony's commercial window was short; by the time the format wars between QS, SQ, and CD-4 had sorted themselves out, the market had largely moved on. The QA-7000's dual-format decoding and synthesis capabilities were, in that context, a hedge against format uncertainty — and a genuinely useful one for anyone who had already invested in quad records.

The complexity of the four-channel signal path — seven-position function switch, dual tape loops, split tone controls, and the matrix/synthesizer circuitry — means that a fully functional example represents a meaningful restoration achievement rather than a simple recap job. The four VU meters, the split tone controls, and the sheer physical presence of the thing make it an object worth owning even if the quad records stay on the shelf.

That is arguably the collector's advantage: the engineering is every bit as serious, the build quality is comparable, and the feature set is broader than almost anything else in the lineup. The penalty is the quadraphonic association, which limits the buyer pool to enthusiasts who either want the four-channel capability or appreciate the BTL flexibility. For anyone in the first camp, the QA-7000 is close to a mandatory piece — it decodes both major matrix formats, synthesizes four channels from stereo, and can record the result. For everyone else, it is a heavy, complicated, beautifully over-engineered stereo amplifier with a lot of knobs that do nothing in two-channel mode. Both descriptions are accurate.

Similar items on eBay

No exact Sansui QA 7000 listings are live right now — these searches show current Sansui 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

• Sansui 2000A (1968-1970)
• Sansui 5000X (1969-1971)
• Sansui 6060 (1975-1977)
• Sansui 7000X
• Sansui 881 (1974-1976)
• Braun AUDIO-1 (1965)
• Braun AUDIO-250 (1965)
• Magnavox Component Systems (1972)
• Acoustic Research AR (1967-1976)
• Acoustic Research 11