Sansui G 5700 (1979-1981)

Seventy-five honest watts, a quartz-locked tuner, and a chassis that runs hot. You'll know it's working.

Overview

The G 5700 is the entry point to Sansui's Pure Power DC Series, a receiver line built around DC-coupled amplification and a tuner section that locks onto stations instead of drifting around them. Sansui's own service documentation rates it at 75 watts per channel into 8 ohms, both channels driven from 20 to 20,000 Hz with no more than 0.03% total harmonic distortion — a conservative, full-bandwidth rating rather than the single-frequency number some brands preferred. The load impedance is specified at 8 ohms, and the amplifier section is DC-coupled with a claimed power-amplifier bandwidth reaching from DC to 200,000 Hz, +0 dB, -3.0 dB. That's the kind of figure that looks like chest-thumping until you remember it's a bandwidth claim, not a power claim: the point is phase behavior and transient response, not ultrasonic output.

The receiver arrived in 1979 as part of a G-series that Sansui positioned as its serious analog hardware. The company's advertising in this period leaned hard on the phrase "quartz-locked tuning does" — a campaign built around the argument that a crystal-referenced tuner holds a station where a conventional analog front end wanders. High Fidelity (September 1979, p.52) ran the copy touting the receiver's electronic LED power meters, which give an instantaneous reading of each channel's output rather than the averaged, damped movement of a needle. Whether you trust a bar of LEDs over a VU meter is a matter of taste, but the meters do respond fast enough to catch transients that a mechanical movement would smooth over.

What owners tend to notice first is the heat. The G 5700 runs warm — warm enough that "Sansui G5700 Heat Problem" is a real thread title circulating among DIY repair crowds, and the compact 465 x 177 x 405mm chassis with its 13.8kg of transformer and heatsink doesn't leave much air inside. That's not a defect so much as a design consequence of squeezing a dual-power-supply DC amplifier into a mid-size case. It rewards owners who give it breathing room and punish those who stack components on top of it.

Key Features

Quartz-Locked PLL FM Stereo Tuner

The tuner is the headline feature, and Sansui knew it — the quartz-lock mechanism was unusual enough at the time that the company built an entire ad campaign around it. Rather than relying on a free-running local oscillator that drifts with temperature, the G 5700 uses a phase-locked loop referenced to a quartz crystal, which holds the tuned frequency steady. The practical result is a station that stays put across a long evening, with none of the slow creep that plagues conventional analog tuners as the chassis warms up. The tuning range covers 88 to 108 MHz on FM. The design also includes an analog tuner section paired with an analog-and-digital frequency display — a transitional touch from an era when digital readouts were arriving but hadn't yet displaced the tuning dial entirely.

Dual Power Supply and DC-Coupled Amplifier

Two separate supplies feed the G 5700 rather than one shared rail, which reduces interaction between channels and keeps the left and right halves of the amplifier from modulating each other under heavy load. The amplifier itself is DC-coupled throughout — no coupling capacitors in the signal path to introduce phase shift or roll off the low end. Sansui's documentation puts the power-amplifier bandwidth at DC to 200,000 Hz, +0 dB, -3.0 dB, and quotes a rise time of 1.4 microseconds with a slew rate of 56 V/µsec. Those numbers describe an amplifier that stays linear well past the audible band, which in practice translates to clean, un-smeared transients. Damping factor is specified at 50 into 8 ohms across 20 Hz to 20 kHz with both channels driven — a solid figure that gives the amplifier real control over woofer motion.

FET Input Stage and Phono Section

A field-effect transistor input stage sits at the front of the amplifier, a choice that typically yields lower noise and a higher input impedance than a bipolar design. The phono input is specified at 2.5 mV with a 47 kilohm load, with maximum input capability of 210 mV at 1 kHz before distortion climbs past 0.1%. Hum and noise figures are quoted at 78 dB on phono and 95 dB on the tape and auxiliary inputs, short-circuited and A-weighted. Channel separation runs 55 dB on phono and 65 dB on line-level inputs at 1 kHz. The RIAA curve deviation is tight — +0.2 dB, -0.2 dB from 30 Hz to 15 kHz — meaning the phono stage tracks the equalization standard closely enough that records sound the way they were cut.

Tone Controls, Filters, and Tape Monitoring

Bass and treble controls offer ±10 dB of range at 50 Hz and 10 kHz respectively, with a defeat switch that takes them out of the circuit entirely when you want the signal path as short as possible. A subsonic filter rolls off at 16 Hz at 6 dB per octave, useful for taming turntable rumble and warp without eating into audible bass. A high filter is provided as well. The loudness control, referenced to the -30 dB volume position, adds 8 dB at 50 Hz and 6 dB at 10 kHz to compensate for the ear's reduced sensitivity at low levels. Audio muting drops the output by 20 dB. There's a tape monitor loop and connections for two tape decks, one line input, phono, headphones, and a microphone input at 6 mV into 10 kilohms.

Historical Context

The G 5700 represents Sansui's late-1970s move into high-power, wide-bandwidth consumer receivers with a clean industrial design — the Pure Power DC Series badge on the front panel was the company's way of signaling that the amplifier section, not the tuner, was the engineering story. The quartz-locked tuner was genuinely uncommon in the segment at the time, and Sansui's advertising leaned on it as a differentiator against receivers that still relied on conventional tuning capacitors. The G-series spanned several models, and Sansui's own service documentation groups the G 5700 with the G-6700 and G-7700 in a single manual — the three share a family resemblance in circuitry and layout, with the G 5700 as the least powerful of the trio.

Sound Signature

The DC-coupled design gives the G 5700 a character that sits between neutrality and warmth — it doesn't editorialize, but it doesn't sound sterile either. Transients arrive with precision, bass stays controlled rather than bloated, and the soundstage opens up without losing focus. There's a subtle richness in the midrange that makes vocals and acoustic instruments feel present rather than reproduced. The 75-watt rating is honest and full-bandwidth, which means it drives moderately efficient speakers without strain and holds composure when the impedance dips. It won't move inefficient modern towers to lease-breaking levels, but for the speakers it was designed to partner with, it has headroom to spare.

Maintenance and Restoration

Electrolytic capacitors are the first thing to fail, and replacing them is close to mandatory before putting a long-dormant unit into regular service. Pots and switches develop crackle over time; a proper cleaning with contact cleaner usually brings them back. The front panel lamps dim and burn out, so spares are worth keeping on hand. Sticky relays are a known issue, particularly in the tape monitor circuit. And given the heat this receiver generates, refreshing the thermal paste on the output transistors is not optional maintenance — it's insurance. A full recap and service can bring a tired example back to near-original performance, and there's no shortage of documentation: the service manual runs 49 pages and is available in French, English, and German.

Collectibility & Value

Collectors rate the G 5700 around 7 out of 10, and asking prices generally fall in the $300 to $600 range depending on condition and cosmetics. Serviced and recapped units command the upper end; unrestored examples with cosmetic flaws sit at the bottom. The model shows up regularly on eBay and Reverb, and parted-out units appear often enough that spare knobs and filter capacitors are findable when you need them. It's not the flagship of the G-series and it isn't priced like one — which is precisely what makes it a sensible entry into Sansui's DC-coupled receivers for someone who wants the sound without the flagship premium.

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