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How long do NOS 6L6gc power tubes last in a Mcintosh MC240 amp?

I just ordered a quad of NOS tubes for the MC240, how long should they last?  I listen for 1-2 hours a day, low-medium volume...
garthb309
tomic601's avatar
tomic601
13,164 posts
 
But the skeptics will ask ( fair ) how do you know ? 1961 Amp store demo came to us in 1965 and went to McIntosh clinics regularly, I remember over many many years a few tubes. I inherited it in 2001 and it finally needed another set. I put the Vintage Tube services set in 3 years ago :-) she beats her spec by 12 wpc
tomic601's avatar
tomic601
13,164 posts
 
Also, if you don’t listen very loud, try light loading the output transformers but dropping down another setting on the impedence- listen also as that is the key - if it sounds better w no clipping keep it that way.
johnss
601 posts
 
tomic601 is correct. the MC240 is pretty easy on tubes. not sure what speakers you are using but try both 8 and 4 ohm taps. usually one will sound a bit better. Also try some KT66s in the 240.
not sure if your 240 is original or not, but greatest improvement you can make is to add a film cap to the 100uf electrolytic cap in the feedback circuit.
Takes longer to remove the bottom cover than it does to solder in the cap, one for each channel.
garthb309 OP
48 posts
 
Thanks @johnss and @tomic601, I have Klipsch heritage Belle speakers, and just ordered replacement tubes from Brent Jessee.
tomic601's avatar
tomic601
13,164 posts
 
Garth - I bet that sounds fantastic!!!! Belles are really nice !
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