The M-22  was a pure Class A amplifier that was rated at 30 watts per channel.  Pioneer stated in its Series 20 brochure: "Class-A circuits are used throughout to reduce distortion.  If operated in Class-B the M-22 would deliver no less than 150 watts per channel--five times as much--with so-so distortion.  The most sophisticated circuit construction yet developed by Series Twenty is reflected here, along with truly first-class parts and components to asssure you're getting the real advantages of such design."

Like the C-21 Preamplifier, the M-22 used metallized polyester capacitors and nichrome-vaporized, metal-coated resistors.  Pioneer utilized a dual mono circuit design and component layout, with a massive power transformer for each channel, coupled with two equally large 22,000 microfarad electrolytic capacitors per channel.  The left and right channel circuitry was mounted to large die-cast finned aluminum heatsinks.  All this was mounted to a rigid die-cast aluminum chassis.

What was striking about both the M-22 and M-25 amplifiers was, of course, their appearance.  Practically all amplifiers in the late 1970s and early 1980s were fully enclosed by sheetmetal on all sides, with a ventiated cover.  Pioneer took the minimalist approach, indeed, a purely industrial design approach to the design of these amplifiers.  All the key components were visible, with the left and right channel components grouped in a mirror image.  This really appealed to audiophiles who truly are intrigued by the "innards" of their electronic components.

And this is what Pioneer had to say specifically about the M-22's performance: "Not to be overlooked is the extremely wide power bandwidth offered in the M-22: 5Hz to 100kHz, both channels driven, 0.01% THD.  Note also that the frequency response is an amazing 2Hz to 150kHz, + 0dB/1 dB at 1 watt, and that the signal-to-noise ratio is a high 106 dB (IHF short-circuited A network."  At its full power output of 30 watts into 8 ohms, this amp had no more than 0.01% THD between 10 Hz and 30kHz!  Class A indeed!

The M-22 had a total of 44 transistors and 66 diodes, for a total of 110 semiconductors.  It measured 16.53 inches wide, 6.03 inches high and 14.56 inches deep.  Its weight was 48 pounds, 8 ounces.  M.S.R.P was $790.00.