Audio, hi-fi and car audio

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- uk.rec.audio (General Audio and Hi-Fi) (https://www.audiobanter.co.uk/uk-rec-audio-general-audio/)

- - Mains filters (https://www.audiobanter.co.uk/uk-rec-audio-general-audio/3807-mains-filters.html)

In article , Glenn Richards wrote:
The theory is sound anyway, if sticking an LCR filter across the mains
input does indeed reduce the noise floor.

Maybe it would be if it did, but it doesn't, so it isn't. It's nonsense.

Rod.

In article , Glenn Richards wrote:
The main reason I was asking... as I said in an earlier post, because I
work from home I've got about a dozen PCs sitting in the next room, on
the same ring main as the hi-fi. Which makes one wonder just how much
crap is getting onto the mains.

Mains is full of crap anyway. Have you ever looked at it with a scope?
Sometimes it looks nothing whatsoever like those neat sinewaves in the
textbooks, but the power supplies in any electronic equipment running from
it will transform it, rectify it, filter it and stabilise it and thereby
turn it into clean DC for the electronics itself because that's what power
supplies do. Filtering the mains will have no additional benefit.

Rod.

"Glenn Richards" wrote in
message
Don Pearce wrote:

Glen,, please give it a rest. You aren't funny any more
and this is all becoming just a little boring.

And herein lies the problem with this group.

I ask a serious question, expecting some sensible
responses, and instead all I get are sarcastic comments.

The theory is sound anyway,

No its not. Contrary to some naive beliefs, there is not a direct connection
from your power line to your speaker cable.

Here's a news flash: there is a fair amount of active and passive circuitry
between your power line and your speaker cable.

if sticking an LCR filter
across the mains input does indeed reduce the noise
floor.

It doesn't. For one thing there already is a massive LCR filter accross the
mains input in just about every piece of gear. It's called the power supply.

As reducing the noise floor (by whatever means)
improves dynamics.

If you want to reduce the noise floor - then why not address the cause of
the noise in the first place? Hint: the source of noise in properly-designed
audio equipment *isn't* leakage from the power line.

And this I have tested, I've recently
been involved in cleaning up some recordings made about
25 years ago on analogue equipment. This process involves
re-EQ followed by digital noise reduction, and the
results before and after applying the noise reduction are
nothing short of dramatic.

Hint: the source of the noise in those old recordings wouldn't have been
helped by power line filters.

This is using Nero Wave Editor (that comes with Nero
Burning ROM), so no fancy expensive software.

You're taking a good idea and running off to China with it.

My question was a serious one, as it's obvious to anyone
with any knowledge of audio that lowering the noise floor
will improve the sound.

Not if the noise floor is already below audibility. And reducing the noise
floor in your stereo will do no good if it is already lower than the noise
floor in the recordings you play.

So, I repeat. If you've got a lot of electrically noisy
equipment on the same ring main as the hi-fi (eg
switching power supplies in PCs etc) that's kicking out a
lot of RF interference on the ring main, would it not
follow that eliminating (or at least greatly reducing)
this noise, and therefore providing a clean power feed to
the amplifier and other equipment, would lower the noise
floor?

Flawed premise. Switching power supplies in PCs don't kick a lot of RF
interference into the mains. They have built in line filters that prevent
that from happening. PC's are widely used for audio production and testing.
They generally don't compromise those environments.

Once again, I'm not for a moment advocating spending £250
on something from Russ Andrews. What I'm actually talking
about is getting a standard IEC lead for a couple of
quid, then fitting a filtered 13A plug to it, also for a
couple of quid. At trade prices in single quantities this
will cost less than a fiver (which is actually less than
you pay for a standard IEC cable at places like PC
World).

Do a sighted evaluation of this idea. I'm sure you'll get positive results.

So, would someone like to provide a serious answer now?

Trust me, if improving sound quality was this easy, it would have been done
all over the place. And in some sense it has - by the plain ordinary power
supplies in regular audio gear.

"Roderick Stewart" wrote in message
om...
In article , Glenn Richards wrote:
I've figured out a method of constructing a filtered power cable for
less than £10 materials cost, depending on quantity. Which, if the hi-fi
mags are anything to go by, will sell for anything up to £60.

And if it does make a perceptible difference, however tiny, that means
£50 profit each time...

And when it is discovered that it makes no difference whatsoever...?

Rod.

This won't affect sales in the slightest. Rod. My local dealer, a good
friend of mine, sells high-end mains cables for EURO 850 each. He
has no stock, and so nothing to "sell" but people still insist on ordering
them!

Iain

In article ,
Don Pearce wrote:
Turn your amplifier on, with no music playing and listen. Leave the
volume control in the normal listening position and sit in your
listening chair. What can you hear? Anything? Of course not. And what
little hiss there is comes from the front end of the amplifier. None
of it comes from the mains.

You've never heard things like a fridge splat etc which is mains borne? Of
course it depends on the design of the power supply in your amp, etc.

I've got a dedicated radial circuit with its own earth feeding my AV
equipment.

--
*I used up all my sick days so I called in dead

Dave Plowman London SW
To e-mail, change noise into sound.

"tony sayer" wrote in message
...
It was eventually determined that there were better, more efficient, and
less troublesome technologies available for broadband delivery, and
dropped,
at least here, although I believe that there may still be some places in
Europe where the tests are still happening. Bear in mind also, that the
generating and distribution companies, use this, or a similar high
frequency
technology, in-house to carry telemetry data around their grid
distribution
network.

What over the 475 kV grid?, don't you mean via the fibre optic at the
top running along the "aerial" earth wire?....

--
Tony Sayer

To Glenn. You've virtually answered your own question there about whether
the mains wiring can successfully handle HF as well as RF, although I was
not actually referring to broadband distribution around the house, rather to
its delivery from the ISP, and this technology has, at least for the time
being, been knocked on the head here, because of potential interference
issues.

To Tony. You're right. In recent years, the electricity companies have
installed fibre optic links, but I'm fairly sure that when they first
started using this method of communicating amongst themselves, they did make
use of the full distribution network, including the supergrid, but I may be
wrong on that. How much power volts are on the line, shouldn't make any
difference. It's still just a piece of wire, with HF skin effect, to the
comms signal. I believe that with the PLT internet trials, the injection
points were at central substations, so I guess that this must have been
working at up to at least the local 11kV distribution level. Just as an
aside, I think that the grid and supergrid operate at 275kV and 400kV, not
475kV. I also have a dim recollection of reading somewhere, that the 25kV
overhead lines on the uk rail nework, were also used for HF telemetry, but
again, I could be going off on one there. Suffering from CRAFTs disease,
don'tcha know ... !! d;~}

Arfa

"Glenn Richards" wrote in message
. uk...
Don Pearce wrote:

I ask a serious question, expecting some sensible responses, and
instead all I get are sarcastic comments.
No, you were trolling.

No, I was asking a serious question.

As reducing the noise floor (by whatever means) improves dynamics.
And this I have tested, I've recently been involved in cleaning up
some recordings made about 25 years ago on analogue equipment. This
process involves re-EQ followed by digital noise reduction, and the
results before and after applying the noise reduction are nothing
short of dramatic.
Cleaning up recordings most certainly does *not* involve eq. That would
be changing recordings.

By "cleaning up" I was referring specifically to applying digital noise
reduction. The re-EQ was mentioned simply for completeness, as the
recordings were a bit bass-shy and lacking in sparkle. So a touch of
smiley EQ solves that, followed by noise reduction.

Professionals call this "cosmetic enhancement" :-))
For one's own use, make any changes that take your fancy.
For a commercial release, I regard the smiley brigade with deep
distrust. When the big day comes and we all standing in line in the
big mastering room in the sky, they will have much to answer for:-)

It's rather vital that you EQ before NR though, otherwise the re-EQ boosts
bits that the NR has cut, leading to some interesting pumping effects...

That's correct. One needs to do a dummy run though to see if the
pre-EQ is the best possible after you have heard the NR.

I do quite a lot of "shellac recovery" Once the surface noise has been
removed, people often get the impression that the HF has been
peeled off also. In actual fact there was probably very little HF
above 6-8kHz there to start with.

So in these instances I do the NR first. Any subsequent gentle
EQ slightly raises the noise floor, but with vintage material is
of little consequence. The secret is to do as little as possible
In this instance less is often more :-)

regards to all
Iain

On Thu, 16 Mar 2006 11:14:28 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
Don Pearce wrote:
Turn your amplifier on, with no music playing and listen. Leave the
volume control in the normal listening position and sit in your
listening chair. What can you hear? Anything? Of course not. And what
little hiss there is comes from the front end of the amplifier. None
of it comes from the mains.

You've never heard things like a fridge splat etc which is mains borne? Of
course it depends on the design of the power supply in your amp, etc.

I've got a dedicated radial circuit with its own earth feeding my AV
equipment.

No - never heard a thing come through the mains. If I started hearing
stuff now, I wouldn't be buying mains filters - I'd be fixing the
wiring.

d

Pearce Consulting
http://www.pearce.uk.com

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.

d

Pearce Consulting
http://www.pearce.uk.com