Cold storage

[Bryn]

If someone you know and like does something for you then you are likely to respond positively.
When I used to work with bands in a studio I would frequently get members saying that the sound of their instrument wasn't good when mixing down (having a band in the room while doing this is a bit of a high risk strategy anyway). So a couple of times I gave the guitarist (and it's often guitarists who are very critical about how their percieve their sound) a channel on the desk which had nothing routed to it. After tweaking the EQ and levels they would say that they were now happy. Psychology is powerful stuff (homeopathic A&E anyone ? )

That'a more the palcebo effecr than homeopathy. Oh, hang on a minute . . .

[Beresford]

Mains cables:

I did have an intermittent mains hum - it would start over a few seconds, then fade after a few minutes. Turns out it was DC on the mains - a few millivolts bias towards either the positive or negative, possibly caused by dodgy electric motor controls somewhere in the village. Evidently this affects equipment with relatively large transformers, like my power amplifier, much more than smaller things. I fixed it with a certain type of filter.

But the sound is still clearer at night. I suspect the neighbours, who use mains to distribute Sky TV round their house, are inadvertently injecting electrical noise. Maybe Nordost cables will fix it.

[jayne lee wilson]

Mains cables:

I did have an intermittent mains hum - it would start over a few seconds, then fade after a few minutes. Turns out it was DC on the mains - a few millivolts bias towards either the positive or negative, possibly caused by dodgy electric motor controls somewhere in the village. Evidently this affects equipment with relatively large transformers, like my power amplifier, much more than smaller things. I fixed it with a certain type of filter.

But the sound is still clearer at night. I suspect the neighbours, who use mains to distribute Sky TV round their house, are inadvertently injecting electrical noise. Maybe Nordost cables will fix it.

Make sure to get an extended home trial, especially on mains gear.

Transformer hum can be a pest.
After 14 years or so, my larger Trichord Powerblock 1000 isolation transformer began to hum annoyingly itself, especially at those morning and early evening mealtimes - and not just in the winter. Nothing seemed obviously wrong with it under the hood, and it was out of guarantee anyway, so I disconnected it and ran sources/preamp off the smaller Powerblock 500 + RA Distribution Block, with the power amp plugged directly into the wall on the 2ndhand Nordost Vishnu (which is how Nordost recommended its use anyway, without filters or conditioners; but their range is very different now). Peace and musical order were restored, and have thankfully remained so.

The larger transformer may have been showing its age, or simply reacting to busier mains nearby.
(And if you do take hifi seriously, powerline broadband adapters are probably best avoided...

[Dave2002]

Make sure to get an extended home trial, especially on mains gear.

Transformer hum can be a pest.
After 14 years or so, my larger Trichord Powerblock 1000 isolation transformer began to hum annoyingly itself, especially at those morning and early evening mealtimes - and not just in the winter. Nothing seemed obviously wrong with it under the hood, and it was out of guarantee anyway, so I disconnected it and ran sources/preamp off the smaller Powerblock 500 + RA Distribution Block, with the power amp plugged directly into the wall on the 2ndhand Nordost Vishnu (which is how Nordost recommended its use anyway, without filters or conditioners; but their range is very different now). Peace and musical order were restored, and have thankfully remained so.

The larger transformer may have been showing its age, or simply reacting to busier mains nearby.

(And if you do take hifi seriously, powerline broadband adapters are probably best avoided...

I am not sure about powerline connectors.
Have you any real evidence that they do cause a problem? I don't mean "do they emit RF noise" - or "do they inject very high frequency noise into the mains", because they almost certainly do, but what I mean is "have you ever really found a problem which is identifiable as due to powerline units?"
If so, how did the problem manifest itself? Otherwise I think that this advice might be based on an urban myth. The whole basis of streaming and wireless audio is centred on high frequency digital circuitry, and we nowadays seem to accept that more or less.

Mobile phones can certainly interfere with computers, and computers can interfere with audio, so anyone who uses computer based kit to play music may experience some problems. A lot of "hi-fi" kit these days is based on computer technology - CDs players, DVD players, and even some amps, as well as internet and digital streamers, so audio might be affected. Perhaps going back to analogue sources and using analogue amps (not that I'd recommend that at all) might actually remove some possible sources of interference and lost quality.

Re transformers, I don't quite see why DC on the mains should have an effect, though there are undoubtedly filters which will take out the DC. For signal lines a capacitor might be sufficient, but for power systems more complex filters might be needed. I once made a valve amp, and couldn't understand why it didn't work. In the end I put a capacitor in the input line, and it worked fine. Being a valve amp, DC on the input was biasing the signal to the valve grid, thus preventing it from working. Transformer cores can become loose and vibrate after a long period, perhaps because of warming etc.

Of course some kit uses switched mode psus, but the general opinion amongst audio enthusiasts seems to be that improvements can be had by ditching those in favour of more conventional transformer based supplies.

[Beresford]

Thanks Bryn and Jayne - points duly noted.
This article (I don't understand all of it) explains how small DC offset affects large torroidal transformers. I use a DC blocker from ADL in Bulgaria.

http://sound.whsites.net/articles/xfmr-dc.htm

My over-simplified view of powerline adaptors is that noise from all that switching finds its way into the mains, and hence into my power amp, albeit at a very low level, but then gets amplified. If you have clean mains, or a regenerator (very expensive), there won't be a problem. (But it is just a hypothesis.)

[jayne lee wilson]

I run Qobuz Studio/Audirvana+ on a Macbook Pro, connected to the DAC via filtered & regenerated USB, the USB Regen powered by its own linear power supply - from which I get excellent results. But even If I have the other Mac running (for reading or writing etc) while a CD, stream or download plays I haven't heard any obvious deterioration. (Maybe those "exotic" cables are actually doing some good...)
But of course, I've read of people who do find computers/phones feeding noise into their music replay.

As Beresford implies, many audiophiles simply want to keep the mains as clear of noise or overuse as possible on principle; I've read several reports of problems with power line adapters in HiFi News and online. For obvious reasons I've never tried them out!

But as ever it will always be very location- and system-contextual.