Monoblock MC275 50th Anniversary tube rolling help (12AX7 on V3, V5 position)

Discussion in 'McIntosh Audio' started by Lockheed Mar, May 15, 2017.

  1. Lockheed Mar

    Lockheed Mar New Member

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    Hi everybody

    I have a question about tube replacement for my MC275 (50th Anniversary version).

    My MC275 is running in monoblocks, so do I need to replace two 12AX7 on V3 and V5 position or just one of them?

    Which tubes (NOS) I should buy? I have Mullard CV4004 on C2300, Shuguang KT-88Z on MC275 and its sound very good.

    I would be grateful for any feedback :)
     
    4-2-7 likes this.
  2. 4-2-7

    4-2-7 Smart Ass Sponsor Subscriber

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    Are the tubes you got with the amp not working, some going bad?
     
  3. Lockheed Mar

    Lockheed Mar New Member

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    It's still working, but I want to make some improvements to my MC275.

    Thanks
     
  4. 4-2-7

    4-2-7 Smart Ass Sponsor Subscriber

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    So does making improvements mean that mac doesn't know what their doing?
     
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  5. Lockheed Mar

    Lockheed Mar New Member

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    The problem is not their amps, but the tubes on its. To me, these currently production tubes are not good as some NOS tubes. This is the reason I want to replace them :)
     
  6. 4-2-7

    4-2-7 Smart Ass Sponsor Subscriber

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    NOS is new old stock, your in the same boat as me and I never see any old tubes that will be enough to fill eight kt 88 holes. This is very close to the same as the signal tubes, you see old tubes that might have good power but it's one or two at a time, then all the other verbalizes. Could take 8 years to find a matching set.

    There is not that many companies manufacturing tubes these days, but they get labeled with many name brands. However mac gets theirs made to spec and then retest them. When I need more tubes for my mac amps I'll just bite the built and get new mac tubes.
     
    Pio1980 likes this.
  7. mkane

    mkane AK Subscriber Subscriber

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    Play around with the 9 pin tubes. Made a big difference here.
     
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  8. Lockheed Mar

    Lockheed Mar New Member

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    Thank you for your feedback :)

    Yes, it's very difficult to find 8 NOS KT88 power tubes. So I would like to replace these 12AX7.

    Do I need to replace two of 12AX7 on the V3L and V5R or one of them? Because I think MC275 monoblocks just use one of those tubes.

    Ps: I have replaced those power tubes with the KT88-Z, and the sound is fantastic.

    Thanks :)
     
  9. 4-2-7

    4-2-7 Smart Ass Sponsor Subscriber

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    Well I wish you luck in your searching, I think the a lot of guys swap the mac tubes for gold lions signal tubes, at least what I'v seen. Oh and welcome to AK and the mac forum, some photos of those bad boys would be nice for use to drool over...:p
     
  10. Seamaster

    Seamaster AK Subscriber Subscriber

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    IMG_3474.JPG

    Lockheed Mar,

    Same here, vintage tubes made big differences in sound, good or bad, it depends on your taste. In my case, there are improvements, in 4-2-7s case, I guess not. What kind of improvements are you looking for in relation to the stock sound? I would start with Holland made Miniwatt, they are very balanced and musical. If you don't mind a reduction in bass, WE 5755 clear top with adapters is about as good as for airiness, 3D, and female vocals for 12ax7 type. Here is a picture of the adapter.


    Also, I tried psvane kt88-tii replaced the stock tubes on my MC75 that made quite improvements in soundstage, imaging, smoothness, dynamic, and attack, yes they can be smooth and dynamic at the same time.

    Owning a tube amp without tube rolling is just missing the half purpose and fun!
     
    Last edited: May 16, 2017
  11. Lockheed Mar

    Lockheed Mar New Member

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  12. Seamaster

    Seamaster AK Subscriber Subscriber

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    That is a wonderful setup! What kind of racks are they? What speakers are you using?
     
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  13. bcarey13

    bcarey13 Back to Basics Subscriber

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    Beautiful setup...very nicely displayed
     
    Lockheed Mar likes this.
  14. damacman

    damacman Blown and Injected Subscriber

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    Lockheed Mar likes this.
  15. Lockheed Mar

    Lockheed Mar New Member

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    I'm using JBL K2 S9900. Those spakers are big but easy to drive. The racks are build from Pyinkado wood.

    Thanks
     
  16. revenoor

    revenoor Active Member

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    Nice, Lockheed Mar! If you look left you might see my avatar is from my time in the Marietta facility.
    Lockheed Mike here
     
  17. x3workshop

    x3workshop AK Subscriber Subscriber

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