"Don Pearce" wrote in message

On Thu, 16 Mar 2006 11:17:50 GMT, "housetrained"
wrote:

Is this the reason why one of my amps has its own power
supply. A separate box that sits next to the pre-amp and
transforms the mains into DC?

All amps have their own power supply that does exactly
this. Whether it is in the same box or not is entirely
immaterial.

True for power amps, but not necessarily true for every kind of audio gear.

Rane, a U.S. pro audio gear manufacturer with a very solid reputation for
conservative technology claims that some of their gear (like mic preamps)
showed a SNR advantage when the power transformer was moved out of the box
and into a big plastic wart on the power cord.

http://www.rane.com/rap.html

Reasons to use external pwoer supples:

"Better Audio Performance. Removes the hum source, i.e. the AC line
transformer and all primary circuits resulting in quieter noise performance,
without the usual (and annoying) 50/60 Hz and 150/180 Hz hum components."