Nasty hum on B channel after Integration upgrade

[kjwcb2]

Hi everyone,
I wonder if anyone could help me with this. I made the Integration upgrade to the Reduction pre-amp (I had the latter running perfectly for 4 months prior to the upgrade) and now I’m left with a nasty hum on the B channel when the volume is over 2 on my main amp. At a lower volume the two channels work fine. I’ve no idea why this is. All the voltage checks are perfect and I’ve checked and/or resoldered all the connections that are related to the upgrade. All the LEDs light up and I’ve tried swapping the valves. Can anyone shed light on this issue?
Thanks in advance.

[Paul Birkeland]

Does this happen when your turntable isn't plugged into the Reduction?

[kjwcb2]

Yes, the hum is present when the turntable is not connected. I've checked the TT with another phono stage and there's no problem with it.

[Paul Birkeland]

I would go back and check all of the ground connections.  An issue like this is almost always a loose wire, and low hum will tend to be a loose ground wire.

[kjwcb2]

I'll do that. Just wondering why the hum doesn't exist at low volume, and the B channel works fine.

[Paul Birkeland]

A loose ground wire could easily cause such an issue.