Denon PMA-390III (1998)

Name: Denon PMA-390III
Brand: Denon

The PMA-390III is a compact integrated amplifier Denon released in 1998 at ¥39,800. It's a refinement of the earlier PMA-390II, and it sits in that late-90s Denon tradition of putting serious circuitry into modest, plain chassis. It's a workhorse with some careful engineering underneath.

What makes the 390III interesting is what Denon did with the power supply and noise control. It uses an HC (High Current) single push-pull circuit, inheriting the concept from the UHC circuit used in higher-end Denon models, and the HC transistors have twice the current supply and peak current capability of ordinary transistors. Fast recovery diodes handle the rectification, and there are dedicated power transformers for the microcomputer and audio circuits separately. Denon also implemented a microcomputer stop mode — when you're just listening, the microcomputer's clock oscillation stops entirely, keeping digital noise out of the audio path. For CD and phono input switching, an inert gas-filled relay is used to suppress switching noise. These are the sorts of details that show where Denon's priorities were.

It's rated at 50W + 50W into 8Ω (20 Hz - 20 kHz) and 100W + 100W into 4Ω at 1 kHz (EIAJ), with THD of 0.02% at 25W/1kHz/8Ω. The line input frequency response extends to 100 kHz. The phono MM stage is respectable for the price: 2.5mV/47kΩ sensitivity, RIAA deviation of ±0.5 dB, and 86 dB S/N. A source direct switch bypasses the tone controls for a cleaner path, and there's a pre-out terminal if you want to add a bigger power amp later. A Rec Out selector lets you dub from CD to MD while listening to a record. The included system remote controls Denon CD players, MD recorders, tuners and cassette decks along with the amp itself. It comes in gold or black and weighs 7.3 kg.

The 390III is well documented on paper, though period reviews are scarce. One repair video on YouTube references a selector malfunction, which seems to be a known failure point worth checking on a used unit. Availability on the used market is decent, and the service manual is obtainable.