MC30 Restoration -- Preservation First! (and caps)

Discussion in 'McIntosh Audio' started by sjfloat, May 13, 2017.

  1. mnmmt

    mnmmt AK Subscriber Subscriber

    Messages:
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    I tried to steer clear of the lettering. The side and top are most visible in my setup.
     
  2. Bill Ferris

    Bill Ferris Well-Known Member

    Messages:
    526
    Location:
    NE. FL.
    IMHO Function before form every time..

    But that`s just me !! I don`t show case my sound reproducing equipment..
    But only listen to it`s primary job..
    If it looks good/great while doing it`s thing, well that`s icing on the cake..

    Some of the best, at least to my ears, sounding reproducing sound equipment I`ve ever heard, has been cobbled together..

    But the sonic results were stellar !!

    But, nobody had a wife or significate other to be concerned about visual presentation..

    As always, just my $ .02 worth.. Regards, OKB
     
  3. sjfloat

    sjfloat Super Member

    Messages:
    1,215
    Location:
    Greater Pittsburgh, PA
    I agree, for the most part. But I'd like to get the rust under control; it's already started to pit a little. And I must admin, the McIntosh black and chrome is kind nice to look at. In the end, it's all aesthetics, whether visual or aural.

    As far as function goes, I'll want quality caps, whichever route I go. I may just put axials inside for now.
     
  4. Bill Ferris

    Bill Ferris Well-Known Member

    Messages:
    526
    Location:
    NE. FL.
    That`s fine, but your doing the job twice..
    My first "tube hi-fi" purchase was in Miami FL. in 1974 and these MC 30`s show the ravages of the salt air that they were exposed to before I bought them inexpensively, used after a Mac clinic finished..
    Then I used them in my electronic test bench as my back ground music w the companion C8/C8S controller/preamps until they went south about a year later..
    And didn`t get around to finally electronically restoring them until year before last..

    Their top chassis` are covered in knarly rust from the original owner`s use + my ownership/storage.. I call it "DNA"
    I personally don`t care what they look like because they well exceed all factory specs. are quiet as a mouse, and have been run for over 56 hours straight, both on the bench and playing music connected to a pair of test/background music sunroom DSCN0097.JPG DSCN0098.JPG
    DQ 10s..

    Right now they reside, as part of my 3 month sunroom tube amp rotation, in the fireplace..
    Not because I`m ashamed of the way they look, but because of the waste heat..
    That I wish to vent outside/attic during the summer here in NE; FL.


    I could have easily replaced their chassis`, but they wouldn`t be the Mac 30`s I bought in 1974 early in my electronic servicing career..
    Same with my MC 225 & MC 60 that I picked up later on..
    Anyway, this is my thoughts on my situation.. Go with yours as you see fit.. :beerchug: :music:

    Kind regards, OKB
     
  5. sjfloat

    sjfloat Super Member

    Messages:
    1,215
    Location:
    Greater Pittsburgh, PA
    Yeah, that's kind of how I feel about it too.

    Say, looks like you're missing your rectifiers. Are you running silicon inside?
     
  6. Bill Ferris

    Bill Ferris Well-Known Member

    Messages:
    526
    Location:
    NE. FL.
    Yes sjfloat, there are no tube rectifier/s in my 30`s or in my single MC 60 that is used as a center channel amp..
    The SS rectifiers are soldered across the rectifier socket, each SS rectifier, in which there are 2 in series from each leg of the power transformer..

    And each rectifier is bypassed with a .01 1kv ceramic disc capacitors(snubbers) + one more from the bridge + to chassis ground.
    The B + line is very clean with no measurable SS rectifier switching noise..

    All my Mac tubers have had their mains tap reset for 125 V, plus a CL80 thermistor on the ones without by design.
    I also removed the 150 ohm 10 watt resistor and replaced it with a choke that`s used in Fender Twin Reverbs..

    I don`t know what the inductance value is(I did many years ago when I bought 20 or so), and really doesn`t matter
    as I empirically tested in one 30 and liked the performance of the PS and sound of the amp under realistic listening levels..

    No mush in dynamic music reproduction allowed here on my watch..

    I personally have never cared for tube rectification in sound reproduction tube amps and have been removing them for years from customers equipment to their satisfaction...

    Now if your talking about a tube rectified guitar amp, then yes, as that is part of the signature/compression tone of a "sound creation' (instrument) tube amplifier when well played..
    Plus the tube rectifier/s are always mounted close to the chassis mounted capacitor and needlessly cooks it greatly reducing it`s life..

    When I do a SS rectifier swap out for the first time I make damn sure the recap can handle the increased cold start surge B+ voltages without having to resort to tube rectifier voltage dropping resistors have to be inserted in the post rectification B+, because the amps dynamic performance is back to tube rectifier I/R voltage drop compression effects...

    Plus the power transformer doesn`t have the 1.5~2.0 or more amp/s of needless tube rectifier filament load and runs cooler..

    "Just my opinion" and the way I treat/deal with customer`s and my tube rectified "sound reproducing" tube amps for over 40 years. YMMV.
    Regards, OKB
     
  7. sjfloat

    sjfloat Super Member

    Messages:
    1,215
    Location:
    Greater Pittsburgh, PA
    Yes, I expect that I'll at least try the SS rectifiers for the reasons you mention. And I agree about the distinction about guitar amps. I have tube rectifiers in most of mine.
     
  8. Bill Ferris

    Bill Ferris Well-Known Member

    Messages:
    526
    Location:
    NE. FL.
    Very well Sir.
    Here`s an interesting story:
    I have my sunroom stereo setup so I can turn on the power switch to the original C 22 preamp, in which by doing so disconnects the feed (output) from my C 27 to my Velodyne active subwoofer`s preamp in + disconnects the MC 2205 input from the subwoofers amps power amp in..
    By that same action also switches 4 30 amp speaker connection relays (1 for each +, and - for switching over to in the NOW current fireplace amps(the MC 30`s..

    Anyway I noticed some months back when the 30`s were brought in for rotation, that when the C 22/MC 30`s were set at the same playback level as the C27/MC 2205 combination, with both fed exactly the same feed from my master A/V living room rack. that I had to turn down the Velodyne`s subwoofer`s level control 1~2 #`s to balance the sub bass output to DQ 10`s..

    Now this MC 2205 has been by me gone through and I have only needed to replace the main filter caps from stock X2 39,000. to 2x 100,000 ufd, so it`s not lacking any PS "beef" what so ever !!
    And it`s my daily driver so I hear it very often as I walk through my sunroom on the way to the garage for a hourly nicotine fix every day 365/7, so no doubt I`m quite familiar with its 20 year sonic presence here..

    So curiously, would you like to speculate why this occurs ??

    BTW the C 22 has been completely checked out and meets and exceeds all factory specs with nothing but D-Oxit to the controls and switches some years ago..

    So I wonder if I unleashed my 30`s bottom end by my PS tweak?
    Regards, OKB
     
  9. sjfloat

    sjfloat Super Member

    Messages:
    1,215
    Location:
    Greater Pittsburgh, PA
    I don't know, but I think it's likely.
     
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  10. Bill Ferris

    Bill Ferris Well-Known Member

    Messages:
    526
    Location:
    NE. FL.
    Mine too, but I might be biased ?!?!
    Just looking for outside respected opinion..
    Crank `er up whenever you can !!
    Live the music as best you can !! Yes ?? :music:
     
  11. sjfloat

    sjfloat Super Member

    Messages:
    1,215
    Location:
    Greater Pittsburgh, PA
    Well, at least in terms of guitar amp rectification, trading squishy compression for a punchier bass is a pretty common trade off.
     
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  12. Bill Ferris

    Bill Ferris Well-Known Member

    Messages:
    526
    Location:
    NE. FL.
    Yes, with a talented guitar player working and milking the amp for what it`s worth has always been a pleasure for me to listen to after a rework of their Fender/Marshall, ect.. It`s really an extension of their guitar & really part of the stringed instrument all it`s self. 120031.jpg 120311.jpg 120545.jpg
    Wrenching those notes naturally out of a properly setup guitar/tube amp is a sonic woody to all exposed..

    A few pictures taken about three years ago of my over 30 year acquired vintage guitar/tube amp collection..

    I have acquired a few more guitars and amps since then..

    I know this is a Mac segment of AK, but thought to convey that I really understand tube rectifiers in their "IMHO" place in tube amplification..
    I thought since your a "picker" you might appreciate some evidence in which I speak..

    Regards, OKB
     

    Attached Files:

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  13. sjfloat

    sjfloat Super Member

    Messages:
    1,215
    Location:
    Greater Pittsburgh, PA
    No question about it. Guitar + amp = instrument.

    Very nice collection.
     
  14. Bill Ferris

    Bill Ferris Well-Known Member

    Messages:
    526
    Location:
    NE. FL.
    Thanks sjfloat, cool thing about all but one amp had been reworked by me for the customer prior to them being offered to me for purchase later..
    So they were turn key, ready to rock & roll.

    No wife, so I can fill up a dining room with some rock & roll history without any grief..
     
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