Mains issues

[admin_exported]

After doing some searching to resolve some problems I'm having I found this.
It's quite interesting that Home entertainment and studios have simular issues.
Any thoughts or views on this are welcome.

http://www.soundonsound.com/sos/Jul03/articles/mainsproblems.asp

 

[Anonymous]

Good grief!

That's a tough read for a Saturday evening. Is there any specific issue you want comments on? What problems are you having?

In general the info is reasonable if slightly out of date. But.....

The author suggests replacing the mains plug to those from "decent brands" with the British safety Kitemark. As far as I am aware the BSI Kitemark can be awarded to products that meet the relevant product standard and have been independantly tested by the British Standards Institute. I don't believe that BS1363, the standard for the UK's 3-pin plug, requires any testing for audio fidelity. It is purely a functional and safety standard. There may be plugs and sockets that sound better than competitors but these can't be derived from the Kitemark. I seem to remember some years back that MK plugs/sockets were supposed to sound better than other brands. MK have always had a good marketing dept. I experimented a bit and I could hear no difference.

I'm not convinced about a radial (the author refers to it as a spur) being significantly better than a ring final circuit. Using "beefier" wiring will reduce the v.d. in the final circuit but this solution also holds true for a ring final circuit w.r.t. v.d. However the current drawn will still cause a v.d. in the upstream part of the circuit. This is why your lights dim when the cooker (or your AV amp) turns on. Earth loops would be another ring vs. radial issue. For a typical domestic / small studio installation, the live conductors for all the installation's circuits come from the consumer unit (fuse box). Any noise generated by equipment on one circuit has a path onto all other directly connected circuits. Hence noise can be transfered from one circuit to another. There would be an amount of attenuation, though quantifying this during design would be very difficult.

The author quotes "For best results, the gear being earthed needs to be near to ground level,...."but doesn't quantify this. With no current flowing through this RF earth, the equipment will be at ground or earth potential. It is only when there is a current flow that the equipment will be removed from earth by a certain potential difference. Greater the current the greater the voltage will be at the equipment earth connection w.r.t earth. Sound advice (if you will forgive the pun) from the author but needs more info to be useful.

Lastly, any article that shows adjusting a transformer with a pair of scissors deserves a healthy dose of scepticism.

I would love to be able to say I understand the whole mains influencing sound quality thing. I can't because I don't. The author of this article has more experience than I do. I can see how a filter block, and even a short piece of audio grade mains cable can change the sound. Subjective evidence shows some people can hear the difference. How it improves fidelity when it is preceded by perhaps hundreds of metres of ordinary mains cable carrying seriously noisy electricity from an industrially wound transformer fed by kilometers of 11kV etc etc......I would like to know!

 

[Anonymous]

Yes quite a big read, my system comprises of QED Qonduit IEC lead for the Amp connected directly to a 3 way wall socket, the Sub connected to the wall socked with standard IEC cable, the input devices are plugged into a Tacima CS929, Sky +,HD DVD player, DAC magic, media extender and Blu ray using a Clearer Audio Copper-Line Alpha. The projector is the opposite end of the room connected to a spur with a Clearer Audio Copper-Line Alpha.
I was quite happy with the system until there was a power cut during a storm, since then the picture from the projector is grainy, although I like the sound.

I'm pretty sure it's a mains issue and I think the noise is coming from the Amp but can't find the cause, I wonder if RCD's can cause these kind of problems even the breaker itself or even a earthing problem, therefore the research.

I'm now thinking of going down the dedicated mains route connecting the projector to this also, I'm not sure if 4mm would be better or stick to 2.5mm it will need to be armoured as it will have to go outside, although the chap writes that a spur is the way to go with this, if you look here http://hiddenwires.co.uk/resourcesarticles2008/articles20080501-01.html recommends to use a ring circuit using Kimber braided cable, I guess he would do as they sell double the amount of cable.

I have also been thinking about a balanced transformer as I've read that noise in the mains can be cancelled out this way, I found this http://www.airlinktransformers.com/transformer/bp1500-bp1500-balanced-power-supply.asp.

Any views or comments would be appreciated.

 

[Anonymous]

uh! give me a while to look at your articles. That's the articles you linked to of course, not your, um, bodily articles. Don't want to see those.

 

[Anonymous]

scowl:
The author quotes "For best results, the gear being earthed needs to be near to ground level,...."but doesn't quantify this. With no current flowing through this RF earth, the equipment will be at ground or earth potential.

I'm familiar with this writer's style... he means that the gear needs to be near ground level not ground potential, i.e. on the ground floor of the building so that the wiring to the earth spike is short and low impedance. If the studio was on the 12th floor of a tower block the benefit of an RF earth would be reduced by its impedance.

Nothing wrong with using a pair of scissors instead of a screwdriver, remember the article is aimed at studio people who aren't as precious about their gear as hi-fi nuts.

 

[Anonymous]

I'd check the projector in another house and see if it is still grainy. Or temprarily feed it from a different ring circuit off an extension lead just to see if you can rule out any common components that could be causing the trouble.

Same with amp and see if noise goes. At least you can rule out any equipment fault/damage due to storm.

Turn the circuit breakers and RCD on/off a few times (off-load) it might clean the contacts. Use TEST button on RCD to make sure it trips ok while your at it.

2.5mm or 4mm depends on volt drop , current carrying capacity and tripping times for your overcurrent protective device. That will need some calcs. I would wire right back to consumer unit if you can. I would not spur as you will lose some of the benefits of a dedicated hi-fi supply. You may not need to use armoured cable. You could offer mechanical protection in other ways.

If you go for the dedicated supply seek professional advice and watch out for part P of the building regs.

I have no experience of balanced transformers so can't comment on their effectiveness but the theory seems plausible.

 

[Anonymous]

try a Tacima mains conditioner .... cheap off ebay (£24) and has good reviews (5 stars from WHI) ... I bought one (delivered yesterday, but have not tested it yet as got home late

 

[Anonymous]

he already has a tacima

if you think its the amp take it out of the circuit do that with the other equipment to see if theyre the problem before thinking about wiring

not sure if kimber and other exotic cables meet the current bs 7671 youd need to check