In article om, David
Lodge wrote:


Is there not another angle to look at (says he throwing fuel on the
cynical fire...) and that is when the mains power supply is noisey.

This is why amplifier designers tend to pay attention to ensuring the amp
has a decent PSU, and has some level of inherent noise rejection. They also
live in the real world. Indeed, the mains supply in many factories or labs
can be even worse than domestic mains in terms of the interference added to
the basic mains waveforms.

While I can appreciate a mains cable ain't going to make any difference
with a clean power supply, to what extent do these noise reducing mains
cables with their ferrite rings and platted cables reduce an
interference that may be inherent in the supply?

Depends. Those that have 'ferrite coatings' would be likely to have almost
no effect on anything except the seller's bank balance. Correct use of
rings, etc, may help in some cases, but this isn't "mains cables" any more.
We are moving into the different topic of "mains filters".


Of course an amp that removes all such interference before the amp power
lines will not show any difference, but will a hifi component with a
less than optimally design power supply benefit from a "noise reducing"
cable?

If the amp and its PSU let through interference, then a filter can help.

FWIW my experience is that some items do produce audible 'clicks' at times
which are mains injected. Reason follows from the above: PSU and rail
rejection not adequate. This can be dealt with by using a mains filter, not
an expensive mains cable. Alternatively, change the item for something else
that has a better PSU and/or amp stages with better rail rejection.

Above said, my experience is also that most items I've used don't have this
problem - or at least it became rarer some decades ago as the designs and
components improved.

Slainte,

Jim

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