"Don Pearce" wrote in message
news:4a3dec21.704992218@localhost...
On Sun, 21 Jun 2009 09:03:51 +0100, Jim Lesurf
wrote:

I got my latest copy of 'Stereophile' yesterday and started to read it. I
came across comments by Paul Messenger about some work that Russ
Andrews and Ben Duncan have recently put onto the web. This seems to be
taken by Paul Messenger as showing that Russ's claims re some of his
products are "now supported by proper scientific analysis".

But having looked at

http://www.russandrews.com/downloads...estPremRes.pdf

http://www.st-andrews.ac.uk/~www_pa/...eshift/cp.html

Interesting. The big problem here is that they were measuring the
wrong thing.

Excellent point.

They should have been measuring effects at speaker
terminals, not on power rails.

Notably, power rails before regulation.

I'll take that as a tacit admission that the regulator made a big
difference, even a bigger difference.

Actually I don't need to get any admissions from them at all, making a big
difference is what regulators do!

My intuition tells me that the audible
difference between 80 and 90 dB of attenuation at the power rails is
going to be close to zero.


Exactly. Furthermore, the fact that their product only made a 10 dB
difference is a clear denounciation of their product.

After all, you must add to that the CMRR,
which is already going to be the right side of 100dB, so effectively
we are talking the difference between -180 and -190. Both of these are
altogether huge compared to what is actually needed.

Also note that the stimulus they were using was a 500 volt peak spike. Ever
see such a thing on a real world power line? Well, maybe once in a blue
moon.

Add to that the idea that 1000V spikes are common enough occurrences
that they impinge on your day to day listening, (rather than being a
"bugger me, what was that?" moment as half the fuses in the house
blow), and require dealing with for listening pleasure.

Agreed.

Of course, if this were a single ended valve amp with no intrinsic
power supply rejection, there might be a case to be made.

Of course they make no admissions that one has to have a stupidly designed
amp for there to be any possible audible benefit at all, except when the
moon is blue! ;-)