Kenwood 400M (1979–1981)

Name: Kenwood 400M
Brand: Kenwood

The Kenwood 400M was the company's flagship power amplifier of its era. It was built to show that Kenwood could compete with the best high-power amps from the US and Japan. It's a hefty stereo amplifier, 26.5kg of it, rated at 200W per channel into 8Ω and bridgeable to mono for 750W into 8Ω. That mono figure says a lot about the current capability the design was built around.

The 400M uses a twin-monobloc internal configuration, with separate power supplies per channel fed by a 1.2kVA transformer, plus a smaller auxiliary supply for the metering and control circuits. It has FETs in the driver stage, balanced XLR and unbalanced RCA inputs, and a damping factor selector. A period review described the styling as classic Kenwood of the late 1970s - black front panel, large illuminated power switch, and a pair of meters. Audio (May 1985, p.108) referenced the model in its classifieds, and the amp appeared in the German market at 1,598 DM in 1980, with UK pricing around £650.

Specs across sources are consistent: frequency response 5Hz–100kHz (+0/–1dB), THD rated at 0.003% at full output, signal-to-noise ratio of 120dB (IHF A network), and a damping factor of 150 at 8Ω. Dimensions are 460 × 185 × 430mm. One point of mild disagreement: the input sensitivity is listed as 1V in the database sources, while the review source gives 0.9V (balanced, 150Ω) and 0.8V (unbalanced, 20kΩ) — a minor discrepancy that likely reflects different measurement conventions rather than an actual design difference.

For a top-tier amp of its day, the 400M's documentation is thinner than you'd expect. Production years are generally given as 1979-1981, though one review places the launch in 1980. Owner reports are uniformly positive, and "dead quiet, huge reserves of power" is a typical sentiment. Owning one today has its costs, though. Capacitors dry out, meters can stick after long idle periods, the bias drifts, and these amps run hot. Kenwood no longer supports the model. Budget for a competent tech who knows high-power amplifier work.