Marantz PM-90 (c. 1986–1989)
It was sold roughly from 1986 to 1989 (some sources narrow this to 1987–88), with a UK price around £450 and a Continental European price nearer €998. The amplifier is often described in period sources as one of the best Marantz ever made.
Electrically, the PM-90 is rated at 70 watts per channel into 8 ohms, with a frequency response extending from 5 Hz to 100 kHz (+0/–1 dB) and total harmonic distortion at 0.02% at rated output. Its phono stage handles both moving magnet and moving coil cartridges — MM at 2.5 mV/47 kΩ, MC at 0.2 mV/100 Ω — with signal-to-noise figures of 86 dB (MM), 74 dB (MC), and 105 dB on line inputs (some sources cite a figure above 110 dB). The line-stage sensitivity is 150 mV into 50 kΩ, and the damping factor is rated at 100. The chassis measures 442 × 147 × 380 mm and weighs 12.8 kg.
Internally, the PM-90 uses a dual-mono arrangement with separate toroidal transformers and power supplies for each channel, discrete-component circuitry throughout, ELNA electrolytic capacitors, and oxygen-free copper internal wiring. The power stage is a symmetrical pure complementary push-pull design, and the first ten watts are said to run in class A. A dual-layer copper-plated PCB carries the circuitry. Inputs include CD, tuner, two tape loops with monitoring, and phono (MM/MC); pre-out/power-in jumpers allow the preamp and power sections to be separated, and there are A/B speaker terminals plus a headphone jack. A volume control and an infrared receiver for the optional Marantz RC-90 remote are fitted, alongside tone controls with defeat and a loudness contour.
There is also a PM-90SA variant, listed separately in most databases. The SA shares the same chassis and 12.8 kg weight but is rated higher at 100 watts per channel into 8 ohms (some sources cite 110 watts into 8Ω), with lower negative feedback, adjustable bias, and an improved phono stage; it reportedly won an EISA award. The standard PM-90's specifications are the ones corroborated across multiple sources; the SA's figures should not be conflated with the base model's.
One note on discrepancies: sources disagree mildly on dimensions (442 × 147 × 380 mm versus 440 × 148 × 382 mm), on the exact production span, and on whether the amplifier's construction is truly dual-mono or a single-supply stereo design — the weight of evidence favors dual-mono.
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