I just got a really good deal on a Randall rg120 Commander II, but it has a hum, or a buzz. It sounds like the buzz that some fluorescent lights make. It's volume follows the master volume control, and it pulses with the tremolo. The channel volumes don't affect the buzz. Also the eq controls act funny. When they are turned to 0 they turn their portion of the signal off. In other words, if they are all turned fully counter clockwise there is no sound. If I turn the bass control up I get volume, but very bassy. If I turn up the mid I get volume in the midrange. Same with the treble. with all eqs on (above 0) it sounds great, except for the buzz. Is the eq supposed to work like this, or is this maybe related to the buzz?
I don't have a schem. and don't know where to get one.
Anyone have an idea about how to fix the buzz?
Thanks

Hi I am new here, and new at building amps. I just ordered one of these
http://cgi.ebay.com/Audio-Power-Amplifier-20W-2x-TDA2003-Assembling-kit_W0QQitemZ230446223553QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item35a7aa50c1
It looks like a really good deal. About $10.00 with shipping, and includes everything but power, speaker, and enclosure.
I'm planning on using the lm386 amp that I already built as a preamp. If I have any problems, I hope I can pick some of your brains.