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Mcintosh 6l6 tube

kennyno

kennyno

New Member
Do all the tubes (6L6) in the mc 240 have to be the same brand .
I see them sold as sets but only need 1 of them to get my new/old 240 up and running.
have 3 that are mc and test good but I only want to replace one with something else for now ?
 
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kennyno said:
Do all the tubes (6L6) in the mc 240 have to be the same brand .
I see them sold as sets but only need 1 of them to get my new/old 240 up and running.
have 3 that are mc and test good but I only want to replace one with something else for now ?
Click to expand...
A lot of push/pull amps require matched pairs of tubes. Not sure if the 240 is one of them. ..Anyone?...
 
From MC240 Owner's Manual p. 8:

IMPORTANT

The excellent performance that is inherent in all Mclntosh amplifiers does not depend on the critical adjustment of bias or balance controls in the output circuit. The patented Mclntosh circuit delivers its advertised specifications without any need for these controls and is not dependent on carefully balanced tubes for its performance. With Mclntosh you can install the amplifier and forget it.
 
For now, one is ok. For best long term service, four new tubes from same brand and lot. I'd go for matched pairs in each channel, just because I've seen what imbalanced output tubes look like at full power from a UC Mac amp on an O'scope.
 
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Fair statement.

Fresh tubes definitely needed to make spec @ full output. Weak/mismatched tubes will reduce the maximum output at rated THD so the question is relative.

In other words, you might have to be content with 20 wpc from your "40-wpc-rated" amplifier in the case of an MC240. But if you're running a pair of K horns, for example, chances are you'd never miss those extra 20 watts - probably even a lot more than just 20.
 
If I remember correctly only the three amp clinics I hosted with DOB in '79 and '80 were clinics where tubes we're replaced N/C. Always all 4 output tubes were replaced, for sure never just one, and I do not remember him doing the owner a disservice of only replacing a channel pair.

The last clinic I hosted with him we did find 4 good tubes of the 12 in the 3 MC240s I had but he only had 8 6l6gc left in his personal stash so I only got his last 8.

A pair should be replaced at the minimum, the only time I would dream of only swapping in one would be if the show had to go on and refunding the audiences tickets was not a option.
 
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