On 2006-03-16, Serge Auckland wrote:

"Iain Churches" wrote in message
...

"Don Pearce" wrote in message
...
On Thu, 16 Mar 2006 10:39:13 +0200, "Iain Churches"
wrote:

Hi Don. I have a feeling you are right. In many years of large
recording sessions, with hundreds of cables and interconnects
I have never seen a mains filter unit in use.

A lot of Pro equipment includes a mains filter as part of the IEC mains
socket. I have VDRs fitted to the plugs feeding all my audio and computer
equipment, as I've found it helps reduce the number of unexplained lock-ups,
when only a power cycle will unlock the kit. I only get one or two a year
now, as opposed to one or two a month without them. I do live out in the
sticks, so my supply may well have less urban hash on it, but possibly more
surges.

As an experiment I have been running my audio kit in recent years from
a single supply point across which I have connected (IIRC):

- A couple of 275 V VDRs in parallel between live and neutral;
- A 220 nF class X2 capacitor from live to neitral; and
- A pair of 22 nF class Y2 capacitors from live to earth and neutral to earth.

Actually I am not aware of any audible difference that this makes
compared to the direct connection. I currently am aware of no audible
"splats" from line voltage anomalies but then again I was not aware of
any beforehand.

I was going to try adding inductances in series with L and N and
bring the filter up to the normal IEC socket filter circuit but since
I perceive no improvement from the above I am not inclined to get out
the soldering iron.

An experiment I recently tried was to burn a dithered -105 dBFS tone at
3 kHz onto a CD. I can hear that as well as the -93.3 dBFS dither noise
if I turn up the gain to maximum. So the mains cannot be interfering
with my kit to that extent anyway.

--
John Phillips