3 Zone Amplifier - was UKHA 2003

["Shane Harrison" <shane.harrison@xxxxxxx>]

Frank asked:

PS Hows the 3 zone amp going any progress ??


For those on the list wondering what Frank is talking about:
I am designing a 3 zone amplifier with digital volume control on it.
For my own use the control is via a Linet network however I have allowed
for RS232 and RS485 on the current layout.  Current layout is a rack
mounted PCB although there is little reason why it couldn't be mounted
in a case with some hefty heatsinks.

Answer to Franks question on progress:
Well it was all going quite well until I accidently allowed a heatsink
>from
- "bugger" as we say downunder.  It took out the 3 digital pots
basically.  However I have replaced those now and have source switching
(1 of 4), power on/off to the amps and the volume control working - all
remotely via the Linet interface. Two problems remain - some 50Hz hum
and the fact the volume is too loud even at the mute level and lowest
volume level.  However some investigation revealed that the amplifier
gain is far to high, which I suspect is the mute problem. Reducing the
gain will also help the hum.  Haven't looked at the ripple on the amp
supply yet but that could also be a source since I am using an old
switch mode supply I had lying around.  So in summary going well and
learning heaps.

Cheers
Shane