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Mains supply and HiFi

a.palfreyman

pfm Member
Well here goes....

I have had my amplifier (NCC200 based) and my pre-amp psu (an old Audio Alchemy dde linear psu) wired into the same plug for many years now as it saves room on the 4-outlet mains block I use. Anyway, despite much fiddling with my DIY speakers, I couldn't get past a certain point WRT reproduction. Middle image a bit ill-defined and what seems like a bit of a 'suck-out' in the upper-mids. Anyway, my B.I.L. gave me a couple of 'special' mains cables (# I'll tell you what these are later...) and on Friday I put the system on and played a couple of CDs. Sounded pretty much as-per normal. Removed the mains lead from the IEC at the back of the power amp and plugged in the 'special' cable. Much to my surprise / delight, the middle image was better rendered, the 'suck-out' was much improved, wider stereo image and a bit better depth rendering too (could be a bit all front-and-back before this change). Anyway, had a bit of a think overnight and realised that I’d effected two changes in one: different lead; and separated the supplies into two plugs.

After a bit of rummaging the following day (Sat), I found another plug. I separated out the original power amp mains lead and pre amp psu mains feed into separate plugs and tried this. Better than the original arrangement, but maybe not quite as good as the ‘special’ lead (would need to do more listening to decide on that one). Anyway after about an hour or so I thought I’d go back to the ‘special’ lead and the thought occurred to me that ‘If this makes an improvement, then I should try the power amp directly into the (double) wall socket and just use the 4-block for low demand stuff’ and sure enough this gave a further small but notable improvement, consisting of slightly more forward mid-range and a slightly wider more projected image. I wouldn’t have believed it unless I’d heard it with my own ears. (Play nicely Jez )

Anyway, I think there is still room for improvement, though I must admit I am very grateful for the ‘nudge’ that forced me into this as I probably wouldn’t have bothered otherwise and been stuck in 'limbo'. So where now? Not sure TBH. It is clear ‘something’ is going on but not sure what (fuse, tarnishing of plug terminals, etc etc)? There are no routers or similar in the house, although most of the lamps are low energy and the effects of these can clearly be seen by holding a ‘scope probe in the air: lots of 50kHz pick-up. However no need to use these in the (long) daylight hours so shouldn’t be causing any problems ATM. I also listen when the Wife is out, so no distractions or mains usage other than the cycling of the fridge.

A final thought / question about class A/B amplifiers: this mode causes ‘a rectified version of the output on the +/- psus’ i.e. positive output swings draw from the + supply rail and negative output swings draw from the – supply rail (my NCCs have separate transformers with the primaries paralleled after the mains switch) but I do wonder if this loading has any ‘strange effects’ WRT 0V plane voltages that could cause a variation of the 0V plane of one channel WRT both the other channel and the pre-amp where the 0V planes are commoned because each secondary half-winding of each transformer sees changing loading conditions that are different plus-to-minus as well as left-to-right? I know a transformer should be ‘fully floating’ but measuring (with a high Z DVM) from the 0V plane to the case earth where the 0v plane is not connected to case earth (e.g. my Farnell sig-gen which has 10nF from 0V plane to case earth as well as a removable earth strap on the output) shows a voltage swing. In fact this sig-gen swings +/-10Vp-p (yes, I did say Volts) at mains frequency so I wonder if this effect can cause earth currents in the 0V plane where the loadings of each winding vary particularly L to R and WRT the pre-amp which these pass through?

# it’s an older style RA ‘YellO’ cable. I used a 1m version on my amp, but was also given a 1.5m version.
 
I use two of those RA Yello leads in my office system. They power my preNCC200 monos and I’ve never dared say it on here before but I’m sure they sound better with than without. I’m a bit of a cable sceptic tbh but I do think cables need to meet a minimum standard.
 
Simon,
I have to go back to 'both in the same plug' to check that out.....
I may just try this after cleaning the plug pins / socket first with Servisol. I'll moisten and insert / remove a few times....
 
Simon,
I have to go back to 'both in the same plug' to check that out.....
I may just try this after cleaning the plug pins / socket first with Servisol. I'll moisten and insert / remove a few times....

I indulged in the final sentence last Friday after a bottle of sparkling. Most satisfying
 
Best upgrade ever for me was installing a dedicated radial with its own MCB in the consumer unit to a double socket in the room 6mm sq cable.
My existing ring goes from my listening room to my kitchen then lounge and dining room. my hifi would sound different at different times of the day, now its very consistently better all the time.

Alan
 
I don't know whether what I did to almost every mains unit in my system might help, but here goes.

In almost every case, I removed the original mains cable. I then made up a 2.5mm substitute mains cable. This is attached to the rear of the unit via a strong cable grip- the type that fits through the case and then locks in place.

It usually involves drilling a larger hole in the chassis.

It looks good- even on my vintage Radford.

The other end is hard wired into the internal side of the chassis, completely shielded with heavy duty mains cable insulation.

This brings a noticeable improvement- perhaps not noticeable if you only do it to the amp- but doing it to every or almost every component...yes. A low cost improvement. No fancy mains cables needed.

I can't offer a technical explanation. At a guess it is the thickness of the replacement cable,with its lower resistance,that accounts for it.
 
A touchy subject, but in my case, the room in which I have my equipment, originally only had one single socket, so I had to fit more sockets like it or not! The house was rewired and I had dedicated supply put in for the hi-fi. It wasn't very costly & was done professionally; a case of fit it and forget it!
 
My system actually sounds a LOT better plugged in to a 20 foot extension lead from a socket in my garage!!
Not a practical solution though and the WAF is -100
So I'm edging closer to a dedicated mains

The whole house was rewired less than 10 years ago....but I did not think ahead (or really give mains much of a thought)
Makes you wonder just what is so wrong that an extension lead can make such an improvement

Ps....house hifi sockets are new MK unstitched
 
They're taking over the asylum....
Sorry Jez, I respect your views, but just reporting what I hear so I have taken SQ's advice. I have cleaned the plug terminals, taken both leads (pre psu and original power amp lead) and cut the ends off and tinned them so they are nice and fresh, putting them both back into the same plug. I have done the same to both ends of my 4-gang lead, plus removed the extra piece and choc-block put on to extend it which I don't now need (forgot about those!) and put it back in place so it is now essentially as before, except now it is cleaned and a potential source of extra impedance removed. Will report back with my findings.
 
It's dead simple. As it is impossible for a mains cable to have any effect whatsoever, any effect you THINK/BELIEVE it has is wrong and is imagined. If I heard a difference with my own ears I wouldn't believe it as I know it's impossible.... hence I'd put it down to too much coffee... too little sleep... whatever...
 
It's dead simple. As it is impossible for a mains cable to have any effect whatsoever, any effect you THINK/BELIEVE it has is wrong and is imagined. If I heard a difference with my own ears I wouldn't believe it as I know it's impossible.... hence I'd put it down to too much coffee... too little sleep... whatever...

You know, if one person, just one person, hears it, they may think he's Really sick and they won't listen to him And if two people hear it -they may think they're both Tories and They won't believe either of them And if three people hear it! Can you imagine three people walkin' in, saying mains makes a difference and walkin' out? They may think it's an Organization! And can you imagine fifty people a day? I said FIFTY people a day Walkin' in, saying mains makes a difference and walkin' out? Friends They may think it's a Movement, and that's what it is THE Pink Fish mains movement!

.sjb
 
Just measure the output coming from the connected device, if anything crops up between 0-120db you've won a prize.


But it won't, because it doesn't make a difference, if it did then at least one company in all of hifidom would have used it in their marketing in the past 30 years, wouldn't they? The closest anyone gets is shenyang showing that mains filtration units lower noise by a few dB in very, very sensitive electrocardiogram machines.
 


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