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

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

  1. bengo

    bengo 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 f'ing 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 Guest

    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...
     
  3. purr1n

    purr1n Desire for betterer is endless.

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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.
     
  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 SBAF's Imelda Marcos

    Staff Member Pyrate BWC
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    Stop being in love. I need to buy your amp!
     
  6. bengo

    bengo Friend

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    I thought they were just regular transistors?
     
  7. AnotherBestAudioFriend

    AnotherBestAudioFriend New

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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 boomer

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    Read the thread....do an Internet search...then ask questions....after you "DON'T BE A DOTARD!"
     
  9. ak2angel

    ak2angel Acquaintance

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    Finally have a chance to officially join the club :D
    [​IMG]
    The exterior is not really in great condition (missing name plate and scratched heatsinks) but interior is fine. Still I got it for one heck of a deal so no complaints.
     
  10. PTS

    PTS Friend

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    Welcome to the club! It's clearly been heavily used, so do yourself a favor and have the electrics checked out by a good tech. It will make a big difference should you need a bunch of components replaced.
     
  11. PTS

    PTS Friend

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    Finally got my M-22 over to Scott Frankland for repair/upgrades.

    Been thinking about trying the M-22 (upon it's return) with headphones via speaker taps, have you guys experimented with that at all? I think Marv somewhere mentioned he though HiFiMan 'phones would work well?
     
  12. bengo

    bengo Friend

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    @PTS Just read my last couple of posts again.
     
  13. foo_me

    foo_me Friend

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    I’ve been using it regularly with the hd800 sdr using a xlr-banana plug adapter off of eBay based upon Marvs suggestion. I was surprised how well it worked. I use the saga as a preamp. Not as smooth as using the ec 2a3 Mkiv but better bass and comparably as detailed. It’s more aggressive with the highs but within the acceptable range.
    It does handle the hd800 with authority.
    The only real negative is the background noise that I hear.

    I wonder how to get rid of it?
    I’m not sure about other headphones but would highly recommend trying the amp with the hd800 at least.
     
  14. m17xr2b

    m17xr2b Friend

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    Is it safe to run a 300ohm load on the amp long term?
     
  15. TomNC

    TomNC Friend

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    This seems a common problem in driving headphones through a speaker amp. It is even harder to eliminate the noise with HD800 versus with less resolving phones such as HD650 or HE6.
     
  16. bengo

    bengo Friend

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  17. m17xr2b

    m17xr2b Friend

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    I'm not touching that again. I have made several of those things even with fancy resistors but you still loose SQ.
     
  18. PTS

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    You got an inaudible noise floor with LCD-XC headphones? They were attached (via adapter) to the M-22 speaker outputs, right?
     
    Last edited: Oct 31, 2017
  19. JK47

    JK47 Guest

    I finally got around to completing the re-cap of my Mitsubishi DA-A10DC.

    Before
    IMG_0510.jpg
    After

    IMG_0513.jpg

    I also switched out the filtering caps which I skipped on the M-22, more on that later. Thanks to this thread on Audio karma I was able to retrofit some new Nichicon caps to replace the old Nichicon Dual C's. http://audiokarma.org/forums/index....ed-some-help-to-bring-it-back-to-life.695867/

    IMG_0514.jpg

    Unlike the M-22 where you see the actual filtering caps, the Mitsubishi's are enclosed in plastic housings. Both the new caps are held in by hot glue and then a secure roll of weather stripping to prevent them from sliding down and shorting out in the amp.

    IMG_0515.jpg
    IMG_0516.jpg
    After a few tracks the Mitsu sounds a little drier and splashy in the treble, but It's not really fair to compare the Mitsu to the Pioneer yet, I'll let the caps settle for a few days before more critical listening.

    The M-22 filtering caps I won in a Yahoo Japan auction for $15 only ended up being $40 to ship. I measured their capacitance and two measured 35,000uf and two measured 32,000uf against their rated 33,000uf. Anyway they are waiting on standby for future installation into the M-22.

    Definitely a fun little project restoring both amps, and I hope to get them somewhere to compare to modern power amps in the future.
     
  20. Cspirou

    Cspirou They call me Sparky

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    I’ve seen PCBs on eBay, but I doubt the transistors are still in production. NOS would have a ludicrous price.

    Speaking of eBay I saw an M-22 listed for $400. However it’s local pickup in Saudi Arabia.
     

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