Kenwood KA-900 (Introduced 1980)
The Kenwood KA-900 is the integrated amplifier that sat at the top of the company's "Purist" line — a serious, no-compromise component from the early 1980s. Introduced in 1980 at an original price of $600, it was positioned as Kenwood's top-of-the-line integrated offering of the era, and it remains one of the more sought-after vintage Kenwood amplifiers among collectors.
Under the hood, the KA-900 is built around a Mos-FET output stage fed by a dual power transformer design with separate power supplies for the left and right channels. That architecture — unusual for an integrated amp of this class — is what gives it the clean, dynamic character that owners consistently praise. A DC servo circuit keeps the output stable, and the amplifier is direct-coupled from its high-level inputs to the speakers when the subsonic filter is switched out. HiFI-Stereo (February 1982, p.42) covered the KA-900 as part of the Purist line, noting the direct-coupled path and the 80-watt rating Kenwood claimed at the time.
Spec-wise, there's a conflict in the record on power output: two sources list 125W RMS per channel into 8 ohms, while one lists 75W. Given the corroboration, 125W is the more commonly cited figure. Frequency response is rated at 20Hz–20kHz (±0.2dB), THD at 0.02%, and signal-to-noise ratio at 110dB (IHF A) — all solid numbers for the period. The phono stage handles both MM and MC cartridges with a 2.5mV input sensitivity and 100mV overload, and it's widely praised for its transparency and low noise floor. Tone controls are present but defeatable, and the damping factor is rated at 50.
Owners describe the sound as warm and detailed with a slight midrange emphasis — a character that suits the Mos-FET topology. The known complaints are minor but worth knowing: there's no relay in the speaker output circuit, so you get a soft "thump" on power-on, and the front panel silkscreening is delicate and prone to wear. Given the amplifier's age, power supply capacitors may need replacement, and spare parts are limited to the usual vintage-gear sources. Current market prices have been rising, with units in good condition typically commanding $300–$400.
Known specs, as documented:
- Power output: 125W RMS per channel into 8 ohms (one source lists 75W)
- Frequency response: 20Hz–20kHz (±0.2dB)
- THD: 0.02%
- Signal-to-noise ratio: 110dB (IHF A)
- Damping factor: 50
- Phono inputs: MM and MC, 2.5mV sensitivity, 100mV overload
- Weight: 26.4 lbs
- Original price: $600
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