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Hitachi MOSFET class A/B stereo power amplifier (Working) - $610 (san jose south)
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The Hitachi HMA-7500 is a high quality 75 watts-per-channel MOSFET class A/B stereo power amplifier.
They are often referred to as the closest thing to a solid state version of a vacuum tube amplifier you can get, only vastly more powerful, cleaner, and faster.
The HMA-7500 is a dual Mono power amplifier, using Power MOSFETs, operating predominately in a Class-A, A/B design.
It runs hot, it's biased for Class-A most of the time. Hitachi discovered a source of distortion was varying capacitance of the output devices near turn-off, so by biasing them more towards Class-A they eliminated this extra source of distortion. Yes it is A Class A/B amplifier but operates more like a Class-A, A/B amp.
This amplifier still sets a high benchmark for audio today, with its surprisingly open, transparent and powerful sound, midrange and upper high signals are sweet, endless, transparent, the bass is firm with authority.
Fast. This amp is fast 20v/uSec slew rate...These 2SK134 and 2SJ49 Power MOSFETs were the fastest audio transistors in the world, and even today the specifications have not been surpassed.
Power Freq Response, DC-100KHz, at 75W/Chan @0.05% THD. Fr+0dB/-0.5dB.