IGC 100 Hz buzz

[vmac011]

I've completed my first unbuffered IGC. I would like to thank to Pedja Rogic and Nick Whetstone for their support. The amp sounds fabulous.
The only thing that irritates me is faint 100Hz buzz that is audible only from close distance from the speaker (~10 cm) and it gradually disappears as the volume control is turned up.
I've used all precautions relating to grounding of the amp. The pot I'm using is cheap carbon 50k log. Could that be a culprit?
Maybe I am too fussy. What is the acceptable level of buzz?
Cheers!

 

[Nuuk]

Nice looking bit of wx-tree there! 😉

I believe that a 20K-25K pot is the optimum for the BrianGT NIGC circuit.

Also, we would need to know more details like what PSU you have. ie one transformer or two etc.

 

[vmac011]

Nuuk,

2 toroids (1 per channel), 2 rectifiers per channel, 4 snubber caps (22nf) per rectifier, PSU box earthed, no connection between PSU and AMP enclosures.
Here's the pic.

Thanks!

 

[vmac011]

And another one

 

[vmac011]

What a hell, here is the zip with all pictures.

I'll try tomorow a better 20k pot.

 

[mhelin]

See this post #78, he recommends that only (-) terminals on bridges are bypassed with the caps. Could they be a just little bit bigger (47nF)?