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

Lockheed Mar

New Member
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 :)
 
So does making improvements mean that mac doesn't know what their doing?

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 :)
 
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 :)
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.
 
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 :)
 
Thank you for your feedback :)

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
 
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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!
 
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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
 
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