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Channel Imbalance Mystery

I’ve been experiencing a channel imbalance for awhile now that I cannot seem to solve. I’m only running a turn table so I cannot troubleshoot with a digital source. I have ruled out the TT and cart as the problem because I had it tested in another system and it sounds great there. I’m running a Herron VTPH-2A phono pre into a Cronus Magnum II integrated amp with brand new KT120 power tubes. (The imbalance was present with older power tubes too). My channel imbalance is left leaning. When I swap the tt inputs into the Herron preamp the imbalance is fixed. Vocals are dead center but my stereo orientation is flipped. No problem, just swap my preamp outputs to get me back to the correct channel orientation but doing so shifts the center image back to the left a bit but soundstage is correct. It’s not nearly as bad as when my tt inputs were in the correct L/R positions. What the hell is causing this?! I’ve tried different interconnect cables with the same results so I don’t think it’s a cable issue. Could it be unmatched signal tubes in the Herron? Signal tubes in the integrated? Super frustrated. Thanks for any help. 
paulgardner
russ69's avatar
russ69
3,360 posts
 
"...Do you know if there one type of signal tube that tends to go bad vs. another?..."

Tubes can go bad at any time. What you do is swap all tubes left to right. If the problem changes sides, move the power tubes left to right and see if it changes. By process of elimination you can isolate the bad tube. 
mglik
884 posts
 
Tubes, tubes, tubes!
Just today, I swapped out Chinese 12AT7s in my Atma MP-1 preamp. Channel balance was ok but the imaging was skewed of to the right. With the new NOS 12AT7s the image is now correct dead center.
paulgardner OP
183 posts
 
@oldhvymec fixed is not the correct word. I would say the imbalance is better but not perfect when I swap the phono RCAs into the Herron then swap the RCA outputs. I called Keith Herron and he thought the same thing as you. Poor connection or bad cables. He also said it’s possibly the tubes so that’s where I’m at after swapping RCA cables and getting the same results. I agree, what’s happening is very odd. I do not get it. 
paulgardner OP
183 posts
 
@mglik thats what I like to hear! I sure hope I get that same results when my replacement 12AT7s arrive. I purchased this preamp used a couple years ago and have only changed a couple of the 5 tubes so who knows how old those AT7 signal tubes are? Thanks for sharing your results after swapping your AT7s!. Appreciate it!
tomic601's avatar
tomic601
12,727 posts
 
there is such a thing as a stereo triode…helps to know both the tube and the topology…

But

Keith will square you away.
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