There seems to be huge confusion amongst audiophiles regarding mains solutions. On one hand you have mains regeneration systems. Turntable power supplies (posh ones anyway) have been doing this for ages but they need a lot less power than an amplifier, for example. Mains regeneration does as it says, it takes the mains, deconstructs it, and then recreates it - hopefully better than it was when it entered. However, whilst it sounds like a great idea there are issues. Specifically, the low impedance of the raw mains it not achieved by (even very large) regenerator. The other problem is that technically competent units are necessarily huge and therefore expensive. Cheaper and smaller units tend, in my experience, make the sound sweeter and smoother but also less dynamic. In fact even vast and hugely expensive units have an element of this too - though peoples sensitivity to this varies enormously.

Separately, there are passive solutions like ‘noise suppression’ and ‘surge protection’. These are really separate issues but surge protection is often just a single component and manufactures love to add it because the cost is minimal and it’s another feature for the marketing department. All the noise suppression and surge protection circuits are of questionable merit as fas as I’m concerned and certainly I have heard such units significantly effect the sound in a negative way.

Then there are DC blockers. This has nothing to do with regeneration and, in theory, DC should not be present on the mains in the first place. However, the reality is that every house my HiFi has lived in has suffered from mains DC issues. Irrespective of appliances in the house the mains fluctuates during the day depending on national usage. The impact of this is that your amp will be quite silent at some times and then humming strongly at other times. Now I don’t mean humming through the speakers, I mean the transformer mechanically makes a noise. How much hum you experience also depends on the type and size of the transformers in your gear. Large toroidal transformers, like the 500VA ones in my power amps, are much more prone to mechanical hum than smaller ones. Now most commercial DC blockers are reasonably small and therefore reasonably inexpensive. However, this also means they are only really effective on lower powered items, like CD players or pre-amps - but then the chance is that such components don’t usually demonstrate this hum problem in the first place. If you put such a small unit on a power amp not only do they not stop the hum but the sound produced is worse - a bit compressed and less detailed (in my direct experience). If you want to reduce DC transformer hum on a power amp you really need a larger DC blocker than those normally sold.

Here’s mine:



Finally, there are balanced mains transformers (one to one) and star earthed mains - both of these are completely separate issues and quite different to any of the previously discussed solutions. I’m sure you are bored by now (I am rather) so I will leave it at that rather than write an even more long winded essay!