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

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

  1. bengo

    bengo Wow, I made it this far without being a friend?

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    Quick update with minimal chain: Pavane > SE > Schiit SYS > SE > M-22 > LCD-XC
    Sys set around 8 o'clock for loud listening :)

    It's definitely tilted towards the top-end, although not really fatiguing. I would also still argue that sub-bass is more emphasized than the rest (I wonder if this translates to speakers).

    Main difference is overall tonality less weird/wonky than (ab)using the Phonitor headphone output as a line out. No obvious big gain in transparency like I expected though (edit: maybe because no longer using the Pavane XLR outs). Phonitor designers knew their shit. Damn, this means I need to trade up to Phonitor 2 eventually, or try some software crossfeed implementations.

    What a fucking treat it is to have an amp like this around. You can try to prize it from my cold, dead fingers, but they won't let go.
     
    Last edited: Oct 4, 2017

  2. JK47

    JK47 Friend

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    Well all righty then, parts from Mouser arrived a few days ago, and this afternoon I dove in and started replacing the caps and trim pots. I wasn't really sure what I was in store for, but it was actually quite easy to get the boards out. Pop off the bottom plate, unplug the connectors, remove 3 screw's that hold the PCB to the heat sink, and the board slides right out, same for the other side. I did one at a time, and replaced each cap one by one, making sure I had the correct value before removing the old and trashing it. Good thing I did, a few caps were different from the parts listed in the US service manual (I have a Japanese M-22), so they will stay in for now.
    IMG_0434.jpg
    Before I started
    IMG_0435.jpg

    Round one done
    IMG_0436.jpg

    The cap and trim pot grave yard
    IMG_0439.jpg
    Both boards (Left and Right channels) are not identical, so if you plan on doing this yourself, look carefully at the parts list for both PCB's in the service manual.

    I mainly used Panasonic FC capacitors with a few NIchicon's in the mix. I cleaned all the pins with a Dremel that the plugs connect to as well.

    I also set the DC balance to 80mV as per the service manual instructions (I know there is controversy regarding this setting that was linked to earlier in this thread), then set the idle current to the 850mV manual spec, and set it again after 10 min, and again after 45 minutes even though it hardly drifted. I checked the DC balance at the same interval's and after 10 min the balance was down to 40mV, after 45 min it was down to 23mV. I did not bother to adjust either channel's DC balance after the initial adjustment, they both dropped uniformly at the same rate.

    I did contact Pioneer USA in the hopes they may have the 33,000uf monster caps stashed away somewhere in a warehouse, yeah right, their response was short and curt. "This amp is no longer in production, check ebay". I did better than that, I checked Yahoo auctions in Japan, and low and behold I won a used set of unknown quality, $20 for all four and $75 shipped for the lot... Shipping hurts, but oh well, feels good to have another set waiting in the wings. This amp has woken up from it's lazy slumber, it has detail and speed that was sorely lacking initially, definitely a keeper.

    Next week I'll tackle my Mitsubishi DA-A10DC, the caps are already here waiting... Mwahahahaaaaa, Pioneer for the mids and hi's, Mitsubishi for the subs...
     
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  3. Marvey

    Marvey Loves sex and records

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    Such a badass design where the engineers had serviceability in mind. As if people were still going to cherish the amp 40 years later.

    The magic is in those transistors.
     
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  4. Armaegis

    Armaegis Friend

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    It's neat seeing the pcb plane designs from back then too. Sorta like electronics meets cubism, except not cubism, some other period that's more squiggly... look I'm an engineer not a painter.

    With all the resurging interest in these amps, I wonder how long before we start seeing an Alibaba clone.
     
  5. zerodeefex

    zerodeefex Ornery Admin

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    Stop being in love. I need to buy your amp!
     
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  6. bengo

    bengo Wow, I made it this far without being a friend?

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    I thought they were just regular transistors?
     
  7. AnotherBestAudioFriend

    AnotherBestAudioFriend Rando

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    What's the power output of the m-22? Does it run speakers at 25-120 watt range/ 6Ω properly? Thanks guys and cats
     
  8. winders

    winders Friend

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    Read the thread....do an Internet search...then ask questions....after you "DON'T BE A DOTARD!"
     

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