On Sun, 20 Apr 2008 19:00:58 -0700 (PDT), EricM
wrote:



Is the buzz affected by the volume control ?

Arfa

There is no volume control as this is a power amp only, however
increasing or decreasing the input signal doesn't affect the buzzing.
Just a 60Hz drone...

It helps if you can check with a CRO to find if it is 60Hz or 120 Hz
(120Hz will come from inadequate filtering in the power supply).

Work back wards logically to find the source. Initially leave only
the output circuit feeding the speaker, and see if the Hum is still
there. Then keep adding stages back to the input till the hum
returns. You are then better able to analyse the situation.

Peter