Harman Kardon PM640

Name: Harman Kardon PM640
Brand: Harman Kardon

The Harman Kardon PM640 is an integrated amplifier, from a period when the company was leaning into its "high-current" engineering philosophy. The record on this model is thin. No production years, original price, or period reviews have surfaced in the accessible documentation. What is known comes from surviving equipment listings and the unit's own design details.

The PM640 is a dual-channel amplifier with a dual-mono-style layout, meaning each channel gets its own power supply section. This was a deliberate choice to reduce crosstalk and improve channel separation. The circuitry is fully discrete, with no ICs in the signal path. The unit also has a relay-based speaker protection circuit, gold-plated RCA jacks, and a built-in MM phono stage with a 47kΩ load. It delivers 45 watts RMS per channel into 4-16Ω speakers. Frequency response is rated at 20Hz-20kHz ±0.5dB and THD is under 0.08%. Signal-to-noise is 90dB on phono and 95dB on line inputs.

Inputs are generous for the era: five line-level inputs plus one MM phono input. There is a pre-out for bi-amping or adding an external power amp, and two pairs of speaker outputs. Tone controls are independent bass and treble with a bypass switch, and there's a loudness contour. The unit weighs 8.5kg and measures 440mm × 120mm × 300mm. Power consumption is rated at 220W.

Beyond the specifications, almost nothing else is documented. There are no known owner reviews, no collector pricing data, no common-failure notes, and no information on how the PM640 fit into Harman Kardon's lineup relative to models like the PM665 Vxi, which HiFI-Stereo covered in its February 1989 amplifier roundup. The PM640 appears to have been a solidly built, thoughtfully specified mid-range integrated amp from a period when Harman Kardon was producing some of its most respected solid-state designs.