Clive, the good news is that if you replace them with plain extension leads with no filtering, surge protection or fancy LEDs, then you should not only get better performance from the hifi but the extension leads are much cheaper too!
However, don’t make the same mistake I have by keeping in a cupboard them “just in case”, because they will inevitably be used again somewhere in the house.
Thanks Richard that makes 9 in total to replace because two of them have LED’s. And yes the plus side is they are a lot cheaper.
One of the cheaper mains blocks that MCRU sells has had the red LEDs disconnected. Probably an easy job for anyone with some basic electrical skills if you don’t want to bin 9 of the things.
Are LED’s really that bad? Back in my ‘youf’ any light indicators on anything in your HiFi was bad. Be that mains leads/blocks or on the equipment itself. I was therefore amazed when I saw that my NAIM equipment came virtually covered in the things - heck it’s like christmas when you turn the room lights off! Further I can’t understand this concept of removing the LED’s from ALL your mains leads and blocks throughout the house, even those not directly connected to the HiFi, when you don’t do anything about all the other, much noisier, devices hanging off your mains e.g. chargers, router PSU, and what about all the LED or CFL lamps you have all over the house?
I had a half decent non surge and non LED block with captive power cable feeding my telly and sky box. Upgraded that for a russ Andrews job which has given better results. But swapped out a belkin surgemaster that was elsewhere in the room that had the phone and device chargers, with the old telly and sky box block - and noticed like Richard posted that it had an effect.
Who says we don’t? 
Not much you can do with a lot of stuff in the house, but when presented with a choice between something like an extension lead with an LED and one without, I would always choose one without. I’m not sure I would go to the lengths of actually replacing one - unless of course it has filtering and anti-surge fitted.
I had a chance to try Gigawatt PC-4EVO power conditioner in my friend’s system and the results are fantastic. But it is an expensive product.
So no phone charges? No led or cfl light bulbs? No power supply on your router? Really?
tbh I think chopping off the LED on a mains block used on a different ring in the house is a waste of time when the listening room has LED lamps in the ceiling or you have a LAN switch with a terrible switch mode plug-top power supply plugged into the mains. However… just my 2ds worth
I’ve never seen an LED on a Mains Block. Neons, yes but no LEDs. I must be missing something here.
You’re probably correct there. I’ve just looked at half a dozen extension mains blocks we use in the office and they all have neons.
Only two of the non surge have lights so spending an extra seven quid to change those is not a problem really.
I said we might do something about it, but I certainly didn’t mean get rid of everything! I don’t think that would be feasible, even for the most dedicated OCD sufferers. You can mitigate any potential effects, though. My dealer turns off a row of downlighters in his showroom during demos because it affects the sound.
@Simon-in-Suffolk opened a thread on the old forum about how to use a portable radio as a basic detector of electrical noise. Prompted by this, I spent an afternoon wandering around the house (while nobody else was in!) looking for culprits. Some ‘low energy’ lights were particularly bad, both CFL and LED. I was sick of the sight of the old CFLs I had anyway, so this prompted me to replace them with LEDs. I found a brand that were very quiet according to the SW radio test (some brands were very noisy) and bought a load of those. I have 3 switches in the house - one was extremely noisy, the other two extremely quiet. iPhone chargers are quite noisy, MacBook chargers less so, but hey, I need my phone, so I use it anyway.
You might, of course, question just how much of this noise actually gets into your HiFi and messes it up. Maybe not much, but it’s not that easy to trace all the potential culprits, so I see this more as a matter of good housekeeping.
Another curve ball for you Richard, what about Powerline Adapters for the net, good or bad with regard the sound?
Aaargh!! Clive, they are the worst!!
If you want an inexpensive way to wirelessly bridge across the house, use something like the apple Airport system, or better still try to get some CAT cable plumbed in.
Hmmm… well homeplug starts at 2MHz so really way up there and very low power. The interference from your average plug top power supply (or LED or CFL) is actually a lot worse… wider frequency and higher power. I know from personal experience you can have big issues with homeplug if you have switch mode power supplies in the vicinity. In fact the power supplies from your Airport units will be throwing more noise onto your mains than if you used homeplug devices
I have two switch mode power supplies plugged into the mains strip along with my NAIM and one of my jobs is to arrange things so they’re getting their power from somewhere else.
Ah well something else to add to the list of things to do. Shouldn’t be that difficult for me to sort out in the coming weeks. And thanks… I think 
It’s a good idea. I keep anything like that on a separate circuit.
Indeed, a different mains block might be better, with as much physical distance between them as possible. The gold standard, though, has to be a dedicated mains circuit for the HiFi.
Yes I’ve just been thinking about it and I think new mains block from one socket for the NAIM and a second mains block (el-cheapo) for the ‘other’ stuff.