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Installed Wrong Tube 12AX& instead of 12 AT7

I just got a MC275 yesterday and the seller mistakenly installed a 12AX7 into the V4 socket (originally for 12AT7) It didn't sound clipped or it didn't stop functioning except that one channel was louder than the other, but I really don't know if the mistake has damaged the amp, or the damage is slightly and I don't see or hear... I am curious to know if anyone has done the same and what happened... Also, what's most likely is to be damaged if this mistake occurs. What should I look out for... or how do I check. All your inputs will be greatly appreciated.
infinity_audio
rodman99999
5,985 posts
 
If you don't match the transconductance of the small signal tubes, you WILL have a channel imbalance(to the degree that the tubes' gains don't match).
casouza
239 posts
 
Rodman, negative feedback (mandatory in a push-pull pentode amp) will offset 90 to 95% of the transcoductance delta.

You are 100% correct regarding 12a_7 tubes in zero-feedback SET amps. These must be matched if you want a central stereo image.
cyclonicman
693 posts
 
One channel would be louder as gain factor for 12AT7 is 60, while gain gactor for 12AX7 is 100. However, the 12AT7 actually has a greater current output than the 12AX7, approx 8-9 times as great.
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