Denon PMA-300ZA (1974)
The PMA-300ZA is a compact integrated amplifier Denon released in 1974 at ¥49,500. It was positioned as an improved version of the earlier PMA-300Z, but surviving sources don't document what was improved. The record does show a 17W-per-channel design (19W per channel with a single channel driven, both into 8Ω at 0.1% THD) with a lot of circuit sophistication packed into a chassis just 376mm wide and 7kg heavy. Some sources also report 22W per channel.
The power stage is a pure complementary OCL design built around Motorola silicon output transistors, with a Darlington-connected driver stage and direct coupling from input to speaker terminals. The phono section has two inputs with different sensitivities (2.4mV for Phono 1, 8mV for Phono 2). That lets you match higher- and lower-output cartridges by switching negative feedback in the equalizer stage instead of adding padding. A 3-stage direct-coupled equalizer amplifier runs from a high +38V collector supply for good headroom. The tone control stage uses a low-noise NPN transistor followed by an FET. The volume control uses a special stepped-resistance curve with an 11-position click stop - a rotary-switch feel with the continuous adjustment of a conventional pot.
Other features: pre-out/main-in jacks for separating the pre and power sections, a -20dB muting switch, loudness compensation, and low- and high-cut filters. A current-limiting protection circuit keeps the output transistors within their safe operating area even under a shorted load. There is a switched and an unswitched AC outlet, and power consumption is rated at 42W.
Information on this model is thin beyond the specifications. No contemporary reviews have surfaced. The only owner commentary comes from Russian forums, where one user reported running the PMA-300ZA daily at a claimed 22W per channel and another, comparing it to a modern Yamaha integrated, found the two very hard to tell apart by ear. A Japanese listing noted the unit was "power-on confirmed." One seller described the design as looking "not quite Japanese, closer to European." Asking prices seen in the wild range from roughly 34,000 rubles (Moscow pickup) to 3.2 million Vietnamese dong, and Japanese auction proxies occasionally list units. No production totals, end-of-production date, or common-failure information is documented.
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