Sansui AU 317 (1977-1979)

Fifty honest watts, DC-coupled from input to output, and a pair of meters that move like they mean it.

Overview

The AU 317 is a DC-powered integrated amplifier from Sansui, sold in the United States and Canada in a 120V/60Hz configuration. Rated output is 45 watts per channel into 8 ohms - the manufacturer's own documentation states that figure alongside total harmonic distortion of less than 0.03 percent. That distortion number is the one to look at. The spec sheet commits to 0.03 percent "at or below rated minimum RMS power output," so the amplifier holds it across the whole rated range, not just at a single test tone at 1 kHz.

Frequency response runs from 5Hz to 70kHz. Power bandwidth is quoted at 20 to 20,000 Hz at or below rated minimum RMS power output. The damping factor is approximately 70 at 8 ohms, which is useful with speakers that have reactive loads. The amplifier keeps a firm grip on woofer motion instead of letting cone resonance smear the lower midrange. Minimum speaker load impedance is 8 ohms, so don't hang a pair of 4-ohm oddities on it and expect it to shrug them off.

Inside the case there are 51 transistors, 25 diodes, and 2 FETs. It's a discrete, component-dense design, not a chip-amp shortcut. The amplifier weighs 9.7kg and measures 430 x 110 x 340mm, the classic full-width, shallow-depth Japanese integrated footprint that stacks neatly under a tuner. It isn't heavy by the standards of the era's monster receivers, but it isn't a lightweight either.

Key Features

Full DC-Coupled OCL Output Stage

The AU 317 is among the first Sansui integrateds with a full DC-coupled amplifier design. Sansui eliminated the output capacitors that sat between the amplifier and the speakers in earlier designs. Those capacitors colored bass response and introduced phase shift at the low end. Per the design literature, the result is tighter bass response and improved signal path integrity. The output stage is direct-coupled OCL - output capacitor-less - the topology that made this generation of Sansui amplifiers feel faster and more articulate than the models before them.

Dual Power Supplies

Each channel gets its own power supply. When both channels share a single supply, a heavy transient in one channel can momentarily starve the other, blurring stereo imaging and compressing dynamics. The AU 317's dual supply keeps the channels electrically isolated from each other's demands, and owners describe the stereo presentation as stable and the imaging as precise rather than smeared.

Phono Stage with MM and MC Capability

The phono input is specified at 2.5mV sensitivity with a 47 kilohm load, and the RIAA curve deviation is held to plus or minus 0.2 dB from 20 to 20,000 Hz — a very tight equalization tolerance for the period. The maximum input capability is 200mV at 1 kHz with total harmonic distortion below 0.008 percent, which means the phono stage has enough headroom to handle hot cartridges without clipping. The AU 317's phono stage supports both moving magnet and moving coil cartridges, making it unusually flexible for an integrated of this class. Signal-to-noise ratio on the phono input is 77 dB, and channel separation is better than 65 dB.

Line-Level Inputs and Tape Loop

Auxiliary and tape play inputs are specified at 150mV sensitivity with a 47 kilohm impedance. Line-level signal-to-noise ratio is 100 dB. There is a dedicated power amp input at 1V/47 kilohms, so the AU 317 can be split into preamplifier and power amplifier sections if you want to insert an external processor or crossover. The tape record output and pre-out deliver 150mV and 1V respectively, and channel separation on the line inputs is better than 73 dB.

Tone Controls and Loudness Compensation

Bass control offers plus or minus 11 dB at 50 Hz, and treble offers plus or minus 10 dB at 15 kHz. There is a phono subsonic filter at -3 dB and 13 Hz with a 6 dB per octave slope, and a high filter at -3 dB and 7 kHz with a 6 dB per octave slope. The loudness control, referenced to -30 dB on the volume control, adds 9 dB at 50 Hz and 7 dB at 10 kHz to restore perceived bass and treble at low listening levels. Sansui also fitted a tone defeat switch, so the tone network can be bypassed and the signal path kept as short as possible.

Dual Power Meters

The front panel carries two analog power meters, one per channel, which move in real time with the music. They are not calibrated laboratory instruments, but they give a useful visual read on how hard the amplifier is working and whether it is approaching its limits.

Historical Context

The AU 317 came out of Sansui's Alpha Series and was built between 1977 and 1979. The DC-coupled topology, the dual supplies and the tight RIAA tolerance all point the same way: solid-state design that is accurate and musical at once.

Period coverage of the amplifier is thin in the surviving record. Audio (October 1978, p.61) ran a survey of integrated amplifiers in that year's buying guide, but the OCR of that page is fragmentary and does not yield clean AU 317-specific measurements. The model sat in the middle of Sansui's late-1970s integrated lineup, and its design language - DC coupling, dual supplies, split pre/power sections - was shared with the higher-end models of the same generation.

Collectibility & Value

Market value for the AU 317 runs approximately $300 to $600 depending on condition and cosmetic appearance, with a collectibility rating of 7 out of 10. It is not a flagship and does not command flagship money. The single eBay listing observed during research was a combined AU 317 and TU 217 tuner bundle at $650. It is undated and covers two components rather than the amplifier alone, so it should not be read as a standalone price for the AU 317.

Buyers should expect to service any example they find. Electrolytic capacitors are likely dried out and should be replaced. Pots and switches benefit from a thorough cleaning to eliminate crackle. The DC offset should be checked and recalibrated, because drift can stress speakers — this is the single most important maintenance item on a DC-coupled amplifier, since there is no output capacitor to block a DC fault from reaching the woofers. Some units develop relay hesitation or flickering meter bulbs, both of which are simple fixes for anyone with a soldering iron and a steady hand. A full recap and service breathes new life into the AU 317 and, by most accounts, unlocks performance that rivals modern gear.