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

Discussion in 'Power Amps' started by Armaegis, Mar 30, 2017.

  1. BearFacts

    BearFacts Rando

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    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.
     
  2. skem

    skem Friend

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    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.
     
  3. BearFacts

    BearFacts Rando

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

    legarem Rando

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    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.
    [​IMG]
     
  5. Tachikoma

    Tachikoma Facebook Friend

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    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.
     
  6. JeffYoung

    JeffYoung Friend

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    "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?
     
  7. Tachikoma

    Tachikoma Facebook Friend

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

    Priidik MOT: Estelon

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    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.
     
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  9. legarem

    legarem Rando

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    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. [​IMG]
     
  10. legarem

    legarem Rando

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    Here are picts

    [​IMG] [​IMG] [​IMG] [​IMG]
     
    Last edited: Jan 29, 2021
  11. Armaegis

    Armaegis Friend

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  12. legarem

    legarem Rando

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    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. [​IMG]
     
  13. legarem

    legarem Rando

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    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 !
     

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