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

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

  1. PTS

    PTS Friend

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    @auvgeek I just checked and there are currently a few people selling ridiculously overpriced units. Either that or the market has suddenly surged without me noticing. I bought a very clean M-22 here on SBAF last December for $850. Didn't need much refurbishing, just a few tweaks. Sign up for free with hifishark.com, and you'll be notified via email when one comes up (it sweeps daily many popular audio sites with a for sale section).
     
    Last edited: Apr 14, 2020
  2. auvgeek

    auvgeek Acquaintance

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    @PTS thanks much for your replies. Really appreciate your time.

    Sounds like a great deal on an M-22. Have you used it with the HE-5se?
     
    Last edited: Apr 15, 2020
  3. Drakkard

    Drakkard Facebook Friend

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    Holly molly. In Russia there are 4 Pioneer m-22's in good condition currently for prices about 400-600$
     
  4. auvgeek

    auvgeek Acquaintance

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    Woah. Even adding the cost of shipping to the US, that's a great deal ... if quality could be confirmed.
     
  5. sp33ls

    sp33ls Friend

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    I just picked up one from Japan for $600 shipped to the US. Overall in good condition. It almost seems like it wasn't really in use all that much, but rather just got tossed into someone's storage and, and as a result, the heatsinks and caps got a little beat up in the process. The bottom chassis is still in great condition. Depending on how things go with this guy, I may end up making a project out of restoring the appearance of the heatsinks. Then again, it's kind of fun to have a "sleeper" amp. An amp that looks like it's been through hell, but sounds way better than it has any right to based on its appearance :p

    I'm still working through a DC offset issue where it now wants to slowly decrease in DC mV over time (as the unit heats up maybe?). I'm in the process of identifying if/where it will bottom out (or if it will then begin to oscillate rather than reach steady-state). These are the joys of vintage equipment I suppose. But, even with an imperfect unit, I can already tell this beast has serious potential as it already has an addicting tone to it. I'm really looking forward to seeing how it performs after my restorations have wrapped up and things are behaving as expected.

    [​IMG]

    EDIT: I also just noticed that the DC offset mirrors the exact AC voltage across the outputs (e.g., one channel is at ~ 70mv DC & also ~70mV AC, with the other being at ~55mV AC & ~55mV DC). Seems like it could be a clue, as I've not observed this before with other amps. Makes me curious to see if replacing the filter caps will result in any noticeable differences with this behavior.
     
    Last edited: Apr 15, 2020
  6. dBel84

    dBel84 Friend

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    That DC is totally acceptable, less than 100mV is nothing to get excited about in a power amp. Obviously ideal if zero but that will not harm the speakers.

    Can't say I have ever measured AC but would expect it to be zero with input grounded

    .. dB
     
  7. PTS

    PTS Friend

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    My M-22 is still in the shop for audio upgrades, and this pandemic is slowing it's return. Should get it back this month. I have heard a number of HiFiMan headphones through the M-22 before (including the notoriously hard to drive HE-6), and it sounded great. @skem has dedicated a great deal of time tweaking his for headphone use. See this thread:

    https://www.superbestaudiofriends.o...r-m22-as-a-head-amp-and-recapping-guide.6717/
     
    Last edited: Apr 16, 2020
  8. sp33ls

    sp33ls Friend

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    @PTS, did you manage to get it back from the shop yet? I'm curious to hear your thoughts.

    I swapped out almost all of the semiconductors minus the output transistors and cleaned up the flux a bit with some isopropyl. I noticed the boards got a little sticky in some areas with the isopropyl. Not sure if it's a bit too strong for these old PCBs?

    Either way, it seems that my wondering DC offset issue has greatly improved. I set it close to 0mV and it seems to deviate between only a few mV's and over longer period of time. I think this may be partially due to thermals, and may be expected with these amps?

    I put some 3.3uF Mundorf Supreme's in mine as well. Tight fit, but managed to find a spot to squeeze 'em in.

    This amp does indeed some wonderful. Coming from a 300B SET, I'm not as used to the "sparkle" in the high frequencies (read: not rolled off lol). I think it's a bit more apparent to me since my main speakers are currently some slightly modified Heresy III's. They're already pretty "non-linear" in their presentation when you crank them up. That poor 12" woofer just can't keep up with the horns.

    Nonetheless, this amp is really cool. Figuratively... it's actually a little space heater. lol
     
    Last edited: May 11, 2020
  9. PTS

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    I'm told "any day now" from the tech. He's been reliable in the past, but this partial lockdown is throwing a lot of people's schedule out-of-whack.

    Glad to see you're digging the M-22. A few years ago we had a shoot-out with an M-22 and a friend's expensive 300B SET amp. We found they were surprisingly similar, with the M-22 being slightly more authoritative (higher wattage) and, as you said, slightly less rolled-off in the highs.
     
    Last edited: May 12, 2020
  10. JeffYoung

    JeffYoung Friend

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    Using a toothbrush or cotton swabs? A toothbrush is good at getting it loose, but then the diluted flux is just spread all over the board making it a bit sticky. A few cotton swabs (ear buds, Q-tips, whatever you want to call them) will actually pick up the diluted flux.

    It's also possible isopropyl will soften an older solder mask, but I've never experienced that. (Do the M22 boards even have a solder mask?)
     
  11. skem

    skem Friend

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    I too had the softening experience with m22.
     
  12. skem

    skem Friend

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    I finally had a chance to try these ITT caps recommended by legarem. They’re not bad! They seem to have less presence than the Audyn Plus caps (white) but I’m not sure that the high treble is reduced. Cymbals and such still seem hot. The ITT might also have a bit more noise pickup, but that’s purely a quick, subjective guess; I haven’t measured.
     
    Last edited: May 18, 2020
  13. legarem

    legarem New

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    Yes cymbals and such are hot. The ITT is finally not a good choice. Probably a really good polypropylene and oil cap should tame this treble. As summer is there, I will begin again tryings this fall.
     
  14. skem

    skem Friend

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    I wonder why an amp that measures flat, and has low odd harmonics, manages to sound hot in the high treble almost regardless of the coupling capacitor. These are the mysteries of the audio world I will never understand.
     
  15. skem

    skem Friend

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    Switching back to Audyn reference. ITT were good caps but recessed in the presence region. Made it sound like everyone had a mild cold. In fact, in side-by-side comparison, the clash of top hats were a bit more aggressive (in a not good way) with the ITTs. If you have weak bass reproduction then I think the ITTs will assist with that by rebalancing between presence region and lower regions
     
    Last edited: May 23, 2020
  16. PTS

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    An argument could be made towards throwing a transparent EQ in the chain (like a Schiit Loki) to reductively fine tune the frequency range. Might be easier than rolling a lot of different components to tune.
     
    Last edited: May 23, 2020
  17. skem

    skem Friend

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    Great minds think alike. But I’m thinking of building a dedicated filter. Loki won’t have the right tuning.
     
  18. JK47

    JK47 Guest

    With summer quickly approaching and the temps rising, I wanted to keep that sweet M-22 sound without suffering from a heat stroke when listening. I decided to track down the Class A/B brother of the M-22... The M-25!!! After a few months I finally spotted a reasonably priced unit in Japan that actually had been recapped (Gold Nichicon), new power lamp (upgraded to LED), new speaker posts, and relays cleaned. Upon arrival this morning I popped open the bottom and confirmed everything was indeed replaced. The M-25 does get warm but not blistering hot like its bro.

    Images from the seller
    M-25_re&re.jpg

    I listened to the Crown CDi1000 for a bit before switching over to the M-25. Oh boy, the M-25 immediately brought a sweeter mid range to the table, and deeper soundstage. I don't expect the same touch as the M-22, but damn this is definitely an upgrade over the Crown. The Crown sounds quite V shaped in comparison.

    Initial power up
    IMG_3112.jpg
    IMG_3110.jpg

    Taking it's place on the Rack of fame with it's brother
    IMG_3113.jpg
    The usual EMS shipping from Japan was not available due to "THE VIRUS", so I was stuck with DHL, which ended up adding another $75 for shipping. Shipping cost almost as much as the amp itself, but still significantly cheaper than anything this side of the Pacific, especially being recapped!!!

    The seller also had a recapped Yamaha B2 that @dBel84 mentioned earlier in this thread, and a Yamaha B3, which I almost caved in and bought as well, both also being recapped...

    I'm quite happy with the purchase, and now I'm bidding on a pre-amp or two from over there as well... teehee.
     
  19. skem

    skem Friend

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    Some people have winter and summer homes, others amps. are those Viawave tweeters? Do you like

    would also be interested in hearing A/B listening impressions with M22, should you feel so inclined.
     
  20. Armaegis

    Armaegis Friend

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    Dude, you need to get those purely for swag reasons and tell us your impressions. My disappointment will be immeasurable if you miss this opportunity to serve the community. :cool:
     

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