XXHighEnd

I build two power filters with Schaffner FN2070 Filter. They can be placed beween a load (DAC, amp, ...) and the wall outlet. I tested different locations, before my dac, before my USB/Spdif converter, my amp and my computer. The intersting thing is, that it makes the sound worse, except if I plug my computer, display and modem behind it. That way, the sound looses some nastyness in the highs. -> So better filter the gear that makes the EMC/EMI!

Or put otherwise : such a filter makes the sound worse. :)
Well, in general.

What type of filter would you use?

That is a difficult question.

Throughout time I have used all sorts of filters, conditioners, offline (sine) generators, and they all have something which I dislike in the end. But I guess, like with cables, I am not keen on such things;
There was a time when I "tweaked" my system with all sorts of stuff, and I imagined they all helped. But in the end you don't know what you are listening to anymore. Also, once you are more into the real sources (which for me obviously is software, DAC, but also speaker crossovers and amps to some extend), you learn that it is not about these "tweaks" at all. Relatively speaking. Other things matter much more, and for digital that extends to "proper matches" if I can call it like that. So for example, a decent digital volume which allows to eliminate the pre-amp from the chain, is a 1000 times more important than decent feet under that pre-amp. Yeah, read again. :)

But once you are finished with all "source" stuff, I guess it may be time to look into filters as well.
But then again, maybe you recall my 17.2 or so KHz distortion from the mains (I posted about this) coming from a pump in my own house; regenerating power couldn't even get rid of it 100% (but sufficiently enough), but while those regenerators caught fire in the end (they really did), later I found that the culprit was to be sought in one of the devices. Today it is a measure for me. If I see that pump again (which always runs), I immediately know something is wrong. A virtue which about nobody will have, but I coincidentally do. The same problem will happen at your place (100% sure), and no external grounding or filtering etc. will eliminate it. Regenerating will only help to some extend. I mean, you won't have such a pump, but I know what to look for (emprical finding) when I see the pump, and for example, I will see my fridge as well (but more down). All sorts of mains distortions will be there. So, they ARE there. But you just must not pick them up. And sadly, I say "you", but it really will be that manufacturer of your whatever device. All it needs is to be plugged into the mains. Switch on is not necessary. Interlinks ? not needed. Only plug it in. And now you will have distortion in everything.

Btw and for your fun ... I never made big fuzz about it, but actually it has been a great discovery for audio. I call it like that, because really nobody could help me with it, and nobody understood what was going on in the first place. But I could "discover" it because I got mad of some actually inaudible tone which nobody heard or got mad of (this was the 17.2 KHz) - and which tone I officially can't hear (it stops at some 12 KHz). So, I started measuring by stupid microphone, and there it was. Up to -60dB. This was also the time I could let see that adding one single connector to a cable would let rise that tone by 3dB or so. A complete cable ? could be 10dB. A most precise "measuring device" !
The tone itself was from PWM by which the pump is rev controlled, and which (I think) shouldn't be there in the (CE certificate stuff) first place. When it would have been at e.g. 24KHz all would have been CE-OK though. Haha;
Because this PWM impeded distortion is a square wave, it spreads throughout the spectrum completely (up to DC) if you only look "deep" enough.
But I said it : the fridge does it too, but at a lower frequency (15KHz) and more down.

All it takes is not picking it up, and regenerating doesn't help (because it will be picked up through air and fed back into everything).

This post helps you exactly nothing; you won't be able to measure it, and next you won't be able to eliminate it.

Yesterday I have been reading this with most interest : http://www.mrec.org/Stray_Voltage/Capacitors%20for%20MREC.pdf
You may start at page 34.
Although hard to get what this is all really about, let's say that this is about this "in-device" stuff. When you started at page 34, it may take a few pages after that before you get the hang of "the" (??) message. Then page 41 comes around. This is crucial. Next are those pages with news paper articles and "claims" for filtering and such. Try to get what this actually is about ...
(FWIW : I agree with it)

Peter

Simple answer: to the computer :)

Thanks Peter for your detailed answer. It helps much more as you think. It is better to know that there is no satisfying sollution and save the money, than beleaving in power reconditioning, that will not help in the end. I realy thought about buying some of the PS-Audio stuff but I feel less temted now. Which is a quiet relaxed state of mind :) I think in some way the same. I don't use stands, expensive cables or all that stuff they want to sell you. Of course good powercables are important and I have good ones. But they don't cost a fortune and I realy don't feel it is necessary to change them. Also relaxing :)
I will read the articel later. Thx.

Yep, that is exactly where my filter was placed after the listening test!

Thanks!

:) But you know why?
Because you have to protect the OTHER components from the noise distributed on the line by the switching PSU.
Filters always work both ways, so you are filtering OUT the noise from the pc.

Yep I know. But after second test all theories seems to fail. The filter before the pc makes the sound dry. So I have build two filters and don't use any of them...Great!