I am finding this thread very interesting from individuals experiences.
There are basically three forms of mains treatments that are popular
Mains regeneration, which is designed to reproduce a greatly improved 50Hz 230Vac wave form
Isolation transformers which all of the outgoing mains voltage passes through first before reaching the audio equipment, this removes a lot of the common mode contamination from the incoming supply.
Mains filtration by using various filters, caps, inductors and discrete circuits to remove the various aspects of mains borne contamination.
Mains contamination has the possible incumbents such as HF noise, Common mode, dc offset, harmonic artifacts.
These are cause by numerous factors:- contamination from factories with large dc motors, florescent tubes, UPS for server back up, lots of medium to high use users in close proximity (light industrial estate) to a residential area, plus many others.
The national grid also carries other signals rather than just 3 phase 440Kv.
Where your place of residence is situated in relation to the nearest supply sub station, pole mount step down transformer etc.
This also have an unpleasant side effect DC offset as the UK domestic grid is single phase 230Vdc though we have measured every thing from 211 to 263Vac here in the last 8 years.
Now there should be NO dc present on UK mains however we have measured in a coupe of places as much as 1.2Vdc which may not sound a great deal however it causes the transformers not to energize correctly so the transformer field does not fully form and is constantly attempting to form the em flux around the TX. This destabilization of the field causing 'humming' vibrating, hence why when you install an isolation transformer the hum transfers from say the amplifier to the isolation transformer. The effect is quite marked.
In one of previous employment positions we use to manufacture large mains regeneration equipment (15Kva and well above) this could be the size of a small family car with an air condition unit attached!
All of the list above treatments work to some extent I would suggest.
In my experience Mains re-generators do have the following positive effects:- Lower noise, improve upper frequency cleanness, better instrument separation and improve bass depth.
The amount of power you require to run your entire system and whether or not the MR device can supply this without either tripping its internal protection or causing a negative sonic change.
The degree of improvement each person achieves depends on how well each of their pieces of equipment reacts to the effects of Mains regeneration. Room interaction issues if present, the quality of the incoming mains.
Isolation transformers (including Balanced which simply means that both the neutral and live wiring is wound equally around the core in opposite directions which is designed to cancel out some of the radiated electromagnetic field) this depends of size of the Tx and the amount of transient current response your require to run your system.
Positive can be improved bass response, lower noise floor coupled with improved overall detail.
Usually these unit are quite large and need to be remote mounted close to the consumer unit especially if over 5Kva.
It is not some much the total size of the tx that is used by more the ability to cope with the dynamic swings.
In the past when installing say a 500va unit into a system that requires a maximum of 360Watts, the performance gained was not in portion to the expense of the unit, only when replacing it with a 1Kva model did the system really shine.
Using a transport / Cd player maybe a maximum of say 30W when running it will require substantially more (in proportion) to when it first starts to spin the disc.
Look at a 30W class 'a' valve integrated this ideals somewhere around 270W! and probably uses only another 30W when running at full tilt.
A few years ago we had a new customer who came from over the pond, brought all his Wilson system with him, he used a BPT 3'5 Kva signature iso transformer. (We have no affiliation to these guys what so ever)
www.b-p-t.com/balanced-power-ultra-isolators.htmlWhich obviously didn't work here in the UK. WE organised a UK tx model for the trip over.
Anyway this is best version of this technology I've have heard to date, outside of the larger 10Kva (UK produced) units we use at Bristol a few times (although it usually required around 15 resets of the rooms internal circuit breaker before the field would energize on that size of transformer!
Lastly passive filtration there are some truly grim and some great implementations of these available to today.
Any item that is connected to the UK power grid in any way domestic or otherwise requires a CE certification and has gone through a battery of directive tests at an approved testing house.
Some use a non invasive method of emi / rfi removal, other uses some for of passive network of caps (must be X and y caps or genuine 668Vac or above rated) to remove certain artifacts on the incoming mains.
So can be described as 'foo' snake oil or of dubious origin!
My point, having tried pretty much all of the methods described above, I have found for a true dynamically unhindered, natural sounding system a combination is required.
This will not be popular however, I do not like mains regeneration in audio, I find it sits on the sound and subjectively puts its own twist on the music. It certainly does improve things no question, for me it takes too much away. However as I have mentioned at the start of the post different systems and personal preferences play a part here.
Iso transformers I feel work better, however you will require a bigger unit than you feel you need to fully bring out the performance of your system.
Passive can work very well, though most do not remove enough of the artifacts to justify their cost.
I could go on about this subject, however I have to put the finishing touches on a project.
Oh last thing I would mention which John has touched on.
Installing a dedicated mains system to your audio system, from experience, 6mm T&E (100mm we found bloated the bass, besides sparkies will whinge about bending 6mm round corners let along 10mm!), switch less sockets and dedicated consumer unit with 16 amp and 32 amp mcb and a 22mm + tail from the meter. All installed by qualified personal and able to supply a certificate of approval for the work.
This will bring a good upgrade to the system for a relatively small outlay.
Earthing is mater you need to discuss with your sparky, there are two types, the old days most people just ran it to a long spike 8 foot underground that was watered regularly. These days you need to be fully aware of the regs'
