Denon PMA-7.5 (1991)

Name: Denon PMA-7.5
Brand: Denon

The Denon PMA-7.5 is a compact pre-main amplifier from 1991. It belongs to Denon’s “Presta” mini-component series, aimed at listeners who wanted serious performance in a small package. Period copy described it as being for “modern fashionable people who are not satisfied with ordinary AV components.” It’s a little-documented model. Even dedicated audio databases carry only a mention, and the Russian-language source that covers it notes that manuals are nearly impossible to find. What the record does show is a genuinely full-scale amplifier squeezed into a chassis just 250mm wide, 96mm tall, and 335mm deep, weighing 5.5kg.

Despite the compact size, Denon packed in a large toroidal transformer for stable current delivery and low leakage flux. There is also a low-impedance volume control that improves the signal-to-noise ratio at normal listening levels. A source direct switch bypasses the tone control circuit entirely. The included remote can also control Denon CD players, cassette decks, and tuners. The system could be expanded by connecting an AV preamplifier, graphic equalizer, or processor.

Rated output is 45W + 45W into 8Ω (20Hz - 20kHz). Maximum practical power is 80W + 80W into 6Ω (EIAJ), and dynamic power is 120W + 120W into 2Ω - the amp is confirmed to operate at 2-ohm loads. THD is rated at 0.008% (1kHz, 22.5W, 8Ω). Phono MM input sensitivity is 2.5mV/47kΩ with a 78dB signal-to-noise ratio at 5mV input. Line input sensitivity is 150mV with 100dB S/N when source direct is engaged. Tone controls are ±8dB at 100Hz and 10kHz. Power consumption is 96W on a 100V AC supply. The unit was made for the Japanese domestic market only.

A related model, the PMA-7.5S, appeared around 1993 at the same ¥49,800 price with essentially identical specs. Its phono S/N is listed slightly better at 84dB, and its line input impedance differs at 15kΩ versus 1.5kΩ. The practical difference between the two is only known to Denon’s Japanese engineers. A later PMA-7.5L from around 1998 was a different beast. It adopted UHC-MOS output transistors and a single push-pull circuit with left/right independent amplifier sections, and it was priced at ¥63,000.

The companion speaker was the Denon SC-410, though the drive2.ru source warns that the surrounds on those are universally deteriorated by now. Original service manuals do circulate among collectors, and used units, particularly the 7.5L, show up on Japanese auction sites and resale markets. One reviewer on YouTube summed it up as “small, but very capable.”

Rated output: 45W + 45W (8Ω, 20Hz–20kHz)
Max practical power: 80W + 80W (6Ω, EIAJ)
Dynamic power: 120W + 120W (2Ω)
THD: 0.008% (1kHz, 22.5W, 8Ω)
Dimensions: 250 × 96 × 335 mm; 5.5kg
Price: ¥49,800 (around 1993)