IGC 100 Hz buzz

vmac011 · 12th October 2004, 02:20 AM

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 · 12th October 2004, 09:16 AM

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 · 12th October 2004, 01:34 PM

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 · 12th October 2004, 01:36 PM

And another one

vmac011 · 12th October 2004, 01:42 PM

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

I'll try tomorow a better 20k pot.

mhelin · 13th October 2004, 07:20 AM

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)?

12th October 2004, 09:16 AM	#2
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	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. __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

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13th October 2004, 07:20 AM	#6
mhelin diyAudio Member Join Date: Apr 2003 Location: Tampere Finland Europe	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)?

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