Pioneer M-22 Power Amp - Epic Japanese Gear From the Past

Thanks for the response. The amp works perfectly even when it is making that vibrating kind of noise - it starts immediately when I flip the toggle switch and sounds like it is coming from around the switch itself...although when I put my hand on the area around the switch, there is no vibration. I put my hand on the transformers and those big caps and there is nothing happening there.

As mentioned, it goes away after 10-15 mins after the amp is warmed up.

 

Well, a 60Hz vibration could be coming from anywhere that has AC current. But usually it's the magnetic field of the transformers. I would open it up and use a mechanic's stethoscope to identify the source of the sound. Just don't electrocute yourself.

EDIT: There is a big ceramic snubber capacitor on the switch. That could be a candidate.

 

Thanks! That ceramic snubber cap sounds like it could be the problem.

 

I had to repair a Linn LK280 amp so by the way, I decided to try it in my system. I am amazed by what I heard. I looked at the LK280 circuit and there's a low pass filter at the input. there's a 1K in series with a 4.7nF that goes to ground at the input stage. I plan to try something like this on the M22 to tame the 'brightness' I consider this amp have. Maybe it will tame the excess of treble of this amp.

 

I just noticed something interesting here:https://skyfiaudio.com/products/pioneer-m22-power-amp-classic-and-unique-piece

This sounds interesting... the mounting looks rather awkward though.

 

"Awkward" might be a little too kind. It looks like they tightened them all until they bent? Or are the TO-3 mounting holes unthreaded with a nut on the back?

 

Just wondering, is there any reason to get a 1500W stepdown over a 2500W stepdown, other than price (and space)?

 

For sound quality reasons, no.
However see to it that the 2.5 kW one has a soft start before it. Very likely will trigger a fuse and maybe even one down the stream in a bigger distribution joint.

 

I bought a cap tester which can also read cap ESR. Today, I measured the four 33 000 uF power supply caps. This was a really good surprise for me. They all test beyond cap values. Since I have this tester I tried it with caps I knew they were bad. It works quite well. I begin to suspect we change good caps because we only think they are too old.

 

Here are picts

 

@legarem you need to share the images rather than copying the url. Try this:
https://www.bettertechtips.com/wordpress/use-dropbox-host-images/

 

Today, I found what I consider the best input cap for the M-22. I had in my stock two 5uF 200V that came from a Classe DR3. They are quite small. I listened them between my preamp and my amp (Linn LK280) and found it mellowed the sound. I installed them in the M-22 and good bye overbright sound. Treble is really like I love. Damn this amp plays well with these. These classe capacitors were made by SiderealKap. Siserealkaps are renowned to be a little dark sounding. The mix with the M-22 is magic.

 

If the Cap and ESR tester interest you, the best price is here:
https://www.newark.com/peak/72-12835/esr-meter-capacitor-1mf-to-22000mf/dp/56Y1286?st=esr70
You can test the caps without taking them out of the circuit. Strangely, it is supposed to work from 1uF to 22 000 uF but it worked very well with the 33 000 uF caps. To be sure, I tested the 33 000 uF caps two in series to be in the range of the tester and it confirmed the correct values. Really great tool !

 

Has anyone compared the M-22 to a Schiit Aegir? I'm looking for a good SS amp and was really interested in the Vidar; however, this thread has me thinking about other options, including the Aegir,,,

If not the Aegir, then what other Class A amps, other than the M-22?

 

Yes, look for @purr1n impressions from a while back, probably in Aegir threads.

 

From https://www.superbestaudiofriends.o...ower-amp-impressions.6953/page-14#post-260399

 

How is this amp at driving difficult 4 ohm loads. I normally use ADS 780 speakers; however, I recently came in possession of older Thiel 1.2’s.

 

I am actually interested in a similar question as I have a pair of 6 ohm speakers and I am thinking about using the M-22 in a Bi-amp configuration for the frequencies above 2300hz.

In the M-22 manual it is specified to use 8ohm speakers only.

 

I own a fully restored M-22 and had dual Aegir's on loan. The Aegir's were good, but the M-22 has a magic that a lot of amps up to $10k couldn't touch IMO. It's a no brainer, if you're up for everything that comes with owning vintage gear.

 

It seems I have decided to transition to tubes and as such am open to selling the M22 that was restored here. It won’t be competitively priced since there is literally 100+ hours of labor in it, but if anybody is interested they can shoot me a PM. With the right transducers, it’s more beautiful sounding than any other solid state I’ve heard including XA25.