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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
paulgardner OP
183 posts
 
@russ69 ok I changed the 12AU7 and 12AX7s in the integrated back to the JJ tubes that came stock with the amp from some Gold Lions and no change. I guess it must be the tubes in the Herron preamp then. I just replaced the 2 12AX7s in the Herron a few months ago so they should be good. I just ordered 2 new 12AT7 to replace in the Herron. Fingers crossed it’s the AT7 that need replacing! Do you know if there one type of signal tube that tends to go bad vs. another? Just wondering. Thanks 
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oldhvymec
5,101 posts
 
My channel imbalance is left leaning. When I swap the tt inputs into the Herron preamp the imbalance is fixed.

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This is the part I don't get, "It's fixed" by swapping left to right. Just the cables right? What do you mean fixed? Imbalanced, you mean one side is louder. Moving a cable is not going to make it right, unless the cable is broke or pulled to tight causing improper contact or pulled wires..

It's fixed means it's fixed.

101 cable.. move the cable and the signal changes something is lose or touching.. Do you have a broken center pin on a male RCA or a center pin broken off in the female RCA? Is it plugged in far enough or to far?

Get your phone and run test tones to check both speakers db level.
Go back from there. You have a test LP or a way to pipe your phone into an input. I use old S3 galaxy phone for head sets and all kinds of things.. Multi DB meters, Source, little mini network, the Wifi still works so does the camera, video, mic, a ton of things. I have a few old G? phones

Plug in to a head phone jack on your amp.

They work perfect for testing STUFF.

You can test right back to the wires for the phono cart if you want.. One cable one tube at a time.

I bet you could put a signal through that Herron via 1/4 stereo plug to L/R RCAs turn the phone down and check left and right signals..

Regards
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. 
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