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Yamaha MX-1 Thread

Discussion in 'Yamaha' started by Bratwurst7s, May 18, 2018.

  1. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

    Messages:
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    Location:
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    It's going to take a little while before this thread really starts to build up steam but it has to start somewhere and so that somewhere is here.

    I've always wanted a CX-1 and MX-1 combo since I first saw them 20 years ago but never figured that I'd be able to afford them.

    Things change and recently it turned out that I could turn my thoughts to buying them. I started with the CX-1 last fall...
    http://audiokarma.org/forums/index.php?threads/yamaha-cx-1-thread.790203/
    ...and then I added an M-70 to the CX-1...
    http://audiokarma.org/forums/index.php?threads/yamaha-m-70-thread.805670/
    ...and then almost 5 weeks ago, on the day that the M-70 first roared to life I found my MX-1.

    I paid the princely sum of €500 for it. A good bit of change but this one is going to be the last one for me I think. Normally I don't do ebay buys without using pay-pal unless it's something real cheap but in this case the seller has almost 2500 actions with 100% rating so I took the chance. As a gesture of being co-operatively nice I doubled his shipping price and asked him to please be careful with packaging.

    He assured me of good packaging, said that it would ship on the next day, and apparently then went on vacation without making sure that it shipped. Boiling down the last 4 weeks one could say that some of my communications were also boiling. But the bonehead finally got it shipped last Friday and it finally arrived today.

    And I have to admit that he did a good job of packaging.

    DSC05314.jpg DSC05315.jpg DSC05316.jpg

    The huge box had massive blocks of styrofoam around the amp, and then 10 layers of thin bubble wrap. It actually took me 40+ minutes and 2 cut fingers to get the amp fully unpacked.

    Cheers,
    James
     
    Last edited: May 19, 2018
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  2. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

    Messages:
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    Upon first inspection it's in pretty good condition visually for a 25yo amp, mainly needs some cleaning. There are a few small scratches, nothing dramatic. Tomorrow I'll open it up and do an internal photo survey and measure the cap sizes and potential room for larger dia caps if that turns out to be necessary. I already have an original service manual from ebay and have made a list of caps. I'll post all of that as we go. Caps will get ordered along with multi-turn idle current trim-pots and relays. I haven't decided yet if the speaker binding posts will be replaced, if so it will be the same ones that I used on the M-70. The pre-in jacks are gold plated solid brass just like the CX-1 and are actually quite nice.

    After that the amp will be hooked up to a dim-bulb tester and if that looks good it will go in the system in place of the M-70. That lets me finish up the final touches to the M-70 and compare the sound of the untouched MX-1 to the re-capped M-70. When the '70 is finished it will be swapped back in and the MX-1 will be pulled and recapped etc before moving permanently into it's new home.

    DSC05318.jpg DSC05319.jpg DSC05320.jpg DSC05321.jpg DSC05322.jpg

    Cheers,
    James
     
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  3. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

    Messages:
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    For reference and interest here a few other AK MX-1 threads that have come up...
    http://audiokarma.org/forums/index....-1-compared-to-other-totl-yamaha-amps.284070/
    http://audiokarma.org/forums/index.php?threads/yamaha-mx1-power-amp-common-ground.636841/
    http://audiokarma.org/forums/index.php?threads/mx-1-a-beast.804359/

    And while wandering around in the net I came across this interesting thread...
    http://liquidaudio.com.au/yamaha-mx-1-power-amplifier-repair/
    A lot of good photos here and some useful info about the soft-start board. Looks like it would pay to copy his work on the transformer solder pads and think about adding a heat sink to the voltage regulator transistor on that board.

    Cheers,
    James
     
  4. 808_state

    808_state Well-Known Member

    Messages:
    750
    I have to admit that now after some break-in, my CX-1 now sounds so good with my B-2x that I'm curious about how it sounds with its intended mate, the MX-1 (but I am re$i$ting). The CX-1 really does give the C-2x a run for its money. Can't wait to hear about your "new" MX-1 once you get it hooked up!
     
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  5. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

    Messages:
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    Location:
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    I've really been loving the sound that I'm getting out of the CX-1+M70 and am very curious how the MX-1 will compare. And after being so pleasantly surprised with the before/after SQ improvement after re-capping the CX-1 it will be interesting to hear how the MX sounds before/after.

    Cheers,
    James
     
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  6. OMGCat!

    OMGCat! AK Subscriber Subscriber

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    Glad it got to you safely even if it was delayed. I bet it's going to make an excellent pairing with the CX-1!
     
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  7. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

    Messages:
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    OK. So this morning I opened it up and took a good look. Took a photo spread, measured the cap sizes and spacing and closed it back up. Before I go into detail about all of that I'm going to jump to a couple of photos of him sitting in place with his soul mate, the sleek and slim CX-1, she's not flashy but oh yeah is she sweet.

    DSC05353.jpg DSC05355.jpg

    Now I'm going to take a nice Saturday afternoon nap. Back in a bit...
    James
     
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  8. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

    Messages:
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    Inside it's immediately clear that this is a completely different beast than the M-70 it's pushing aside. The construction quality is in a completely different world. Every component ID is silkscreened on both sides of the pcbs. The amp boards are mounted directly to their heatsinks. Not only that the output transistors are mounted to a sub-heatsink that is screwed to the main heatsinks so that the boards can be pulled from the heatsinks without having to de-solder the OT's and the OT's have silpads. And there are those 2 big transformers.

    This amp was apparently from a non-smoker, no yucky brown coating on any of the surfaces. The insides are remarkably dust free, the entire insides are very clean.

    DSC05323.jpg DSC05324.jpg

    Cheers,
    James
     
  9. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    The PSU has only 5 elcos mounted.

    The 4 main filter caps, Nichicon, 2x 33000µF/50v and 2x 36000µF/40v, 50x70mm and there is no room for anything larger in dia or taller. They have the newest date code that I could see, N9950. So this is a very late production amp when one considers that 2000 was the last year it was sold.

    Then there is a single little 2.2µF/50v Elna Duorex, C13.

    DSC05325.jpg DSC05326.jpg DSC05327.jpg DSC05328.jpg DSC05329.jpg

    Each channel has a pair of heatsink mounted common ground rectifiers.
    Notice how clean the board is, I haven't done any dusting or cleaning yet.

    Cheers,
    James
     
    Last edited: May 19, 2018
  10. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    The protection board has 4 caps and the relays. The board actually stretches all the way across the back, partly under the V-Amp board.
    C253 is fairly well hidden in the right side of the board, 0.22µF/100v, 6mm x 10mm. it's really hard to tell but it looks like a Nichicon. Will be replaced with a Wima MKS2.
    C254 = 10µF/16v Elna Duorex, 6x10mm. If there is room a MKS2, if not a Panasonic FM or FC, probably 35v.
    C255 = 220µF/6.3v Duorex, 8x12mm, there is room for 10mm dia. Panasonic FM, 10v or 16v.
    C256 = 10µF/16v Duorex. Same as C254. Room for at least 8mm dia.
    RY101, 102 = DE2TU 24vDC. 18x30x30mm. I still have to look up a sub. I have 2x relays left over from the M-70 project, I'll have to see if they will work.

    DSC05330.jpg DSC05331.jpg

    Notice that the complete speaker binding post assy is gold plated, even the legs on the inside that connect to the protection board.

    Cheers,
    James
     
  11. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    The V-Amp board is mounted vertically, all the way in the back of the case. It has 7 elcos.
    C18, C19 and C39 = 1000µF/100v Elna. I measured these and just realized that I failed to record the numbers. This kind of PO's me because they are size critical. I believe that they were 22x30mm but will have to go back in and check this.
    C28, C29, C42, C43 = 100µF/10v Duorex, 6x10mm with room for 8mm dia. Panasonic FM or FC, 16v or 25v.

    DSC05332.jpg DSC05333.jpg

    Cheers,
    James
     

     

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  12. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    The main amp boards, Right channel...

    DSC05334.jpg DSC05335.jpg DSC05336.jpg

    ...
     
  13. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    ...and Left channel.

    DSC05337.jpg DSC05339.jpg DSC05340.jpg

    There are a total of 10 elcos on the 2 boards.
    C201, C202, C203, C204, C205, C206 = 47µF/16v, Elna Duorex 6x10mm, looks like there is room for 8mm dia. I'll probably just keep right on using Panasonic FM or FC here, 25v or 35v.
    C237, C243, C244, C250 = 100µF/50v Elna Brown, 8x12mm. Room for 10mm dia. Again, probably FM or FC.

    Cheers,
    James
     
  14. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    That's all that there is concerning elcos except to say that there are no elcos in the signal path that I can find.

    There are a fair number of carbon film resistors in the signal path.
    R78, R79 = 470ohm 1/3w.
    R19, R25 = 100ohm 1/2w.
    R63, R64, R73, R74 = 100ohm 1/4w fusible/flameproof.
    The I-Amp has 12 each 4.7ohm 1/4w fusible/flameproof, as well as...
    2x 22ohm 5w,
    2x 4..7ohm 1w. (I forgot to record the positions of some of these, I'll look at the schematic and edit this section later).

    There are also 6x diodes in the signal path, D24, D25, D26, D29, D30, D31 = 1S133. I might look up their specs and see if a Vishay SBYV27 ultra fast, soft recovery will work here.

    I also still have to look up some Bourns or Vishay/Dale 20 turn trim pots for the idle current adjusters, side mount.

    Cheers,
    James
     
  15. avionic

    avionic " Black Knights " Subscriber

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    Found a few bad solder connections on the transistors (VAS) on both the MX-1 and MX-2 I have.
    [​IMG]
     
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  16. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    So before I took my nap I did a noise test, turning up the volume with no source playing. Dead silence at any volume. Then I played 1 song for starters, "I'm A Man" from Chicago's 1st album. This one is a pretty good all 'rounder for a test song.

    1st impressions: I'm going to like this amp. It displays similar clean and crisp fantastic mids and highs like the M-70 but it was immediately clear that this amp is working better with the Speakerlab's woofers. Tighter and cleaner bass. This is going to be fun. I'm going to turn it back on in a little while and do an extended listening session.

    Cheers,
    James
     
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  17. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    Thanks Avionic, I will definitely be re-flowing every solder connection in the amp. :thumbsup::)

    Cheers,
    James
     
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  18. avionic

    avionic " Black Knights " Subscriber

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    MX-1 is definitely a keeper...
     
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  19. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    Oh heck, I almost forgot to show the front mounted soft-start board.

    My model doesn't have the regulator transistor shown in the article that I linked to. Just 1 elco, C17 470µF/25v Elna brown.
    RY2 = DH1U 12vDC relay.

    DSC05341.jpg DSC05343.jpg DSC05345.jpg DSC05347.jpg DSC05349.jpg

    Cheers,
    James
     
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  20. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    Dang. I'm getting really forgetful. Before putting the amp in the system I checked the DC ofset after letting it warm up a bit. Note that I haven't checked the idle current yet.

    The DC offset fluctuated a bit but settled on an average of 2.3mV left and 2.4mV right. I guess that I can live with that. ;):)

    DSC05350.jpg DSC05351.jpg

    Cheers,
    James
     
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