I bought a 48 pound solid-state (SS) monster, the Class A Pioneer M-22 reference amp, for $250 about over a dozen years ago because I couldn’t stand the scratchy sound of my rusty Dynaco ST70s with their compliment of 4-EL34 tubes. The closest modern day Pioneer equivalent is the Elite series M-10x, which it looks more like their current receivers than it looks like my amp. My black beauty looks like Theshold amplifiers shown at the 2000 CES show: enjoythemusic/ces2001/monday/. (The new Threshold Pro company is going to release this amplifier shortly along the lines of the old Threshold T300 amplifier and priced at approximately $8,000.) The top of the M-22 is exposed. It has two hefty black transformers, square and 4” high with two black 33,000 uF capacitors the size of Foster lager cans, are surrounded by a fortress of black cooling fins. The four computer grade storage capacitors reduce power supply ripple to about 1/10 volt. The SS Pioneer is 30 watts per side, dual mono amp with dual transistor differentials built onto one chassis. It is 2-stage differential push-pull Darlington connection, direct coupled OCL. It has plentiful negative feedback in the 1st stage. I bought it cheap, new and in the box. Frequency response is from 2 Hz to 150 kHz within 1 dB. Like any solid state amplifier, the Total Harmonic Distortion (THD) is a U shaped curve. It is .005% at 1 watt into 8 ohms at one end, dips below .001% at 15 watts, curving back up to .01% at 30 watts at the other. In other words, ultra clean response. Below 10 watts, the M-22 has better THD spec than the Krell FBP 350mc at $17,000 per pair! It has better THD, wider frequency response and greater signal to noise ratio than a $6,000 Mark Levinson 431. Technically the amp can put out more than 30 watts, but the THD climbs like a rocket once output is higher than 22 watts. Hence the M-22 designation. Below one watt, the THD curve is just as high as it is above 30 watts! Stereophile magazine formally defines clipping as the 1% THD+noise figure. This gives the M-22 a maximum power delivery of a solid 60 watts into 8 ohms (26.8dBW), way above the specified power ratings and more than typical at home listening requirements in normal size rooms. Power consumption is 280 watts. By the way, the god of huge power amps has an interesting article at his web site (passlabs/articles/seclassa.htm). Nelson Pass himself patiently explains the allure of … not huge SS amps, as you might think, but simple designs like tube amps: “Regardless of the type of gain device, in systems where the utmost in natural reproduction is the goal, simple single-ended Class A circuits are the topologies of choice.” With my big old Klipsch Cornwalls, I figure I might be using .0785 watt at normal listening levels. Musical SPLs average in the mid 60s to mid 70s; fast musical peaks are 15 dB higher. However at that those low levels, the THD is as high on the chart as 30 or 35 watts. In other words most of the time, the amp is averaging THD of a few percent – not unlike a tube amplifier. Apparently this amp was made to show off Pioneer’s designing ability – and it does. It is very clean. I hope to use it to power a pair of electrostatic headphones someday soon. I only had to take it in once for repairs. The workman could not stop praising the quality of it and all it had was a blown fuse (located inside). 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 youre 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 sheet metal on all sides, with a ventilated 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-22s 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. (About $3,127 in 2008 dollars.)
Posted on: Tue, 18 Mar 2014 01:46:05 +0000
Trending Topics
Recently Viewed Topics
© 2015