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Power Cables. Are they overhyped?

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Listening tests or listening panels do not advance the science behind power cables in any way.

For one thing, we can not guarantee an individual will be consistent. Over time our hearing deteriorates anyway.

Why wouldn't you spend the additional money re-engineering the internals of your ampl?

We do know how to engineer good regulated power supplies; implement a good earthing arrangement; separate noise generating elements from the audio stages; even create constant current sources.

Or...are we saying that we are assuming that the amplifier has been fully optimised before we look at mains feed?
 
sq225917 said:
He's right though. Anyone trying to sell you a fancy power cable oven a decent spec mass produced iec is a charlatan.

Bill, I have two sets of Amps, a Muse model 200 that will spit and crackle if I move cables around and hums and buzzes from the speakers. It's been serviced in the past five years and measures to spec, it's just poorly designed with bad wiring that picks up all sorts of noise.

My other power amps are Tom Christians mod86p parallel amps. These are strewn across the floor with all sorts of poor cable layout, my laziness, but the circuit is balanced and has over 90db of PSRR. It's utterly silent at my typical max listening level.

One is designed well, one isn't.

I build a lot of phono stages. And am very careful with wiring layout and earth connection quality. It makes all the difference in the world to measured noise and hum.
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Thanks for responding SQ and BE - you can rest assured that I'm not in the market (at the moment anyway) for any fancy cables, but am thinking through the issues 'academically'. (I do have an electronics degree and was a Chartered Enginner, so do have some understanding of the issues, but this was long ago and I'm now a farmer!)

I have some kit purchased secondhand that was originally expensive (eg Conrad Johnson CA200 amp, original cost $6500) that I'm happy with, and have been for some years, but it's Class 1 and unbalanced - and I'm not planning any kit changes in the near future.

So moving to double insulated and balanced is not on the cards. We then come to the electrics in my house - it's a TT system where the earth goes to an Earth spike and eventually back to the Neutral back at the transformer. This transformer is a couple of fields away. (It's not a PME system where the Neutral and Earth are tied together at the entry into the house.)

My original question (I think) was whether anyone had any experience as to whether a low impedance (to high frequencies) connection to Earth might be of benefit. I understand that noise signals on the earth line will be 'finding' routes back to the 'source of the voltage' - which in my case I suppose will be the 11kV to 240v transformer a few fields away.

Any experience or thoughts?

The reason I'm thinking about this issue is not that I've got a problem, but that I'm probably going to be doing some house rewiring in the not too distant future, and am wondering what things might have an impact.

Cheers. Bill
 
Sure, put in a dedicated radial to the hifi, but I really wouldn't bother doing anything further with the cabling unless you identify a specific issue.
 
BilliumB said:
My original question (I think) was whether anyone had any experience as to whether a low impedance (to high frequencies) connection to Earth might be of benefit.
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The snag with the above is what it means in practice once you get to frequencies such that even a few metres of cable can't be regarded a very short compared to a wavelength. Similarly, what it means when the ground is also conductive (which of course, it needs to be if someone is going to bang a connection into it and call it 'ground').

Under these sorts of circumstances 'Earth' or 'Ground' may not means a flat 0V electrostatic potential. And the actual potential may change from one place to another.
 
Yes, now I think we're talking along the same lines.

Jim do you think some form of earth coax connection (using both the core and screen connected at the earth spike end, core connected at the kit end) might be worth exploring? Obviously safety regs will have to be followed, and quality of earth spike network / earth mat or similar will be critical.

At some point I'll probably have to get hold of a 'scope to see what's going on.

Cheers. Bill
 
BE718 said:
Sure, put in a dedicated radial to the hifi, but I really wouldn't bother doing anything further with the cabling unless you identify a specific issue.
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Hi BE - I guess I'm thinking ahead - doing something further at a later date would be fairly disruptive in terms of taking floors up etc. At the moment I'm just trying to get my head around the possibilities.

I've got a digger, so sorting out an effective earthing network may not be too much of a problem, and I don't mind a project!

Cheers. Bill
 
BilliumB said:
Yes, now I think we're talking along the same lines.

Jim do you think some form of earth coax connection (using both the core and screen connected at the earth spike end, core connected at the kit end) might be worth exploring? Obviously safety regs will have to be followed, and quality of earth spike network / earth mat or similar will be critical.

At some point I'll probably have to get hold of a 'scope to see what's going on.

Cheers. Bill
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Still not sure what you are trying to achieve here. Earth coax?

You talk about low impedance at high frequencies as if you are convinced there is say an RF problem on your earth wiring, and coax as if it needs to be shielded. Why do you think this?
 
BilliumB said:
Yes, now I think we're talking along the same lines.

Jim do you think some form of earth coax connection (using both the core and screen connected at the earth spike end, core connected at the kit end) might be worth exploring?
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Again, you'd have to think about what *kind* of RFI injection mechanism you have in mind. In particular, bear in mind that domestic mains wiring isn't only LNE to wall sockets. It also had spurs of LN to room lights where only one wire is switched at the wall. This means the domestic wiring is nothing like any kind of RF transmission line you'd ever dream of using as such!

Particularly when a room light is 'off' the resulting N wire up to the light acts as an antenna lined to the N, with no parallel connected to the L. Switch the light on, and the behaviour changes. Similarly, moving something like an anglepoise lamp about also changes things.

From a RFI POV normal home wiring is a shambles. I'll add a part two for a specific case.
 
Some years ago I was taking to a BBC Engineer about measurements he was making wrt the effect of 'powerline' adaptors. Those PITA boxes that deliberately squirt garbage into the mains. There was one paper in the literature where this made the lights on an xmas tree act like an antenna. 8-]
 
Well BE, I don't know (no test equipment), but I would guess that the earth connection on the ring main to my kit is likely to have a noise voltage on it - probably at frequencies well above 50Hz. I would also guess the impedance of the earth within the 2.5mm twin and earth cable (probably 1.5mm) is likely to present quite a high impedance to such noise. So, if I can provide a low impedance path to this ground noise back to a system of earthing, and hence back to the transformer, I'm wondering if this might provide benefit. I'm wondering whether coax cable might be a way of achieving such a low impedance path.

In a way, I'm looking at how I might be able to improve my set-up by thinking things through rather than randomly trying out different bits of kit and listening to the result. A problem I have currently is a lack of test equipment (in the past access to £50k analysers, oscilloscopes etc was not a problem).

Cheers. Bill
 
Jim Audiomisc said:
Again, you'd have to think about what *kind* of RFI injection mechanism you have in mind. In particular, bear in mind that domestic mains wiring isn't only LNE to wall sockets. It also had spurs of LN to room lights where only one wire is switched at the wall. This means the domestic wiring is nothing like any kind of RF transmission line you'd ever dream of using as such!

Particularly when a room light is 'off' the resulting N wire up to the light acts as an antenna lined to the N, with no parallel connected to the L. Switch the light on, and the behaviour changes. Similarly, moving something like an anglepoise lamp about also changes things.

From a RFI POV normal home wiring is a shambles. I'll add a part two for a specific case.
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Hi Jim, these are exactly the kind of issues I'm thinking about. I'm wondering how to get the best quality earth at my hifi kit. I'm looking at a separate Consumer Unit and Radial, also wondering about the best form of radial cable. I've been thinking about twisted pair or BE's star quad as a way of minimising pickup but have not yet found anything rated for mains use. My electrician has suggested using split concentric cable for the basic radial and I'm investigating. In addition, I'm wondering about some form of parallel earth connection, possibly coax based, but am unsure whether it is likely to provide a benefit.

(Must go out now, back in a few hours! Thanks very much for taking an interest.)

Cheers Bill
 
As Jim is alluding to above the method of injection into the wiring is potentially very complex.

You arecalso assuming that the alledged noise is going to go away because you have reduced the impedance to earth.

Unfortunately what you are doing here is no less random than trying different bits of kit.
 
BilliumB said:
Well BE, I don't know (no test equipment), but I would guess that the earth connection on the ring main to my kit is likely to have a noise voltage on it - probably at frequencies well above 50Hz.
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Where do you think the noise would be coming from?

I'm wondering whether coax cable might be a way of achieving such a low impedance path.
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The only reasons to use coax is if you want to shield a signal, while providing a known (not very low) specific impedance at RF frequencies. If you want to provide a low impedance path, straight copper is best.
 
BilliumB said:
Hi Jim, these are exactly the kind of issues I'm thinking about. I'm wondering how to get the best quality earth at my hifi kit. I'm looking at a separate Consumer Unit and Radial, also wondering about the best form of radial cable. I've been thinking about twisted pair or BE's star quad as a way of minimising pickup but have not yet found anything rated for mains use. My electrician has suggested using split concentric cable for the basic radial and I'm investigating. In addition, I'm wondering about some form of parallel earth connection, possibly coax based, but am unsure whether it is likely to provide a benefit.

(Must go out now, back in a few hours! Thanks very much for taking an interest.)

Cheers Bill
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Chances are that is would be simpler and more effective to put filters on the mains at the point where it enters your equipment.

You can buy these quite cheaply and quickly from CPC / Maplin / etc. So it is easy to give it a try. Once done you can spend the time and money on more music. :)
 
Julf said:
Where do you think the noise would be coming from?



The only reasons to use coax is if you want to shield a signal, while providing a known (not very low) specific impedance at RF frequencies. If you want to provide a low impedance path, straight copper is best.
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Hi Julf

Thanks for getting involved. As to where the noise might be coming from, I'd guess it's mainly from normal stuff in the house as the nearest neighbour is a few fields away. However the mains quality in general may be poor due to milking machines and similar on neighbouring farms (however on our 11kV to 240v transformer there is just 1 other property - although he does use a fair number of machine tools). As I'm on a TT system I do of course have an independent earth connection. We're tucked down in a valley so the RF environment is probably not too bad. I'm really just wondering if I can make a difference - without test equipment I don't really know how bad things are. (As a separate issue, I do get transformer buzzing issues, probably dc on the mains, not fully solved by a dc blocker and isolation transformer, voltage at 249v is also high.)

As to straight copper, I guess you mean copper strip, and may well be correct - I remember we used to use similar at the radio station, and it's often used for lightening conductors where I guess high frequencies (fast pulses) are likely to be an issue. Do you know of any good sources for such material - I probably need around 25m?

Cheers. Bill
 
Jim Audiomisc said:
Chances are that is would be simpler and more effective to put filters on the mains at the point where it enters your equipment.

You can buy these quite cheaply and quickly from CPC / Maplin / etc. So it is easy to give it a try. Once done you can spend the time and money on more music. :)
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Hi Jim, you may well be right but as I'm planning to install a radial I don't want to waste the opportunity if I can improve things.

As to mains filters I already use an MIT Z Powerbar filter that I got at a very good price second hand (I think it originally cost well over £1k) and it does make a difference, so I guess there probably is noise there! However I was wondering if this filter will be adding to the noise on the earth line? If so, even more reason to look a earth impedance?!

Cheers. Bill
 
BilliumB said:
Hi Julf

Thanks for getting involved. As to where the noise might be coming from, I'd guess it's mainly from normal stuff in the house as the nearest neighbour is a few fields away. However the mains quality in general may be poor due to milking machines and similar on neighbouring farms (however on our 11kV to 240v transformer there is just 1 other property - although he does use a fair number of machine tools). As I'm on a TT system I do of course have an independent earth connection. We're tucked down in a valley so the RF environment is probably not too bad. I'm really just wondering if I can make a difference - without test equipment I don't really know how bad things are. (As a separate issue, I do get transformer buzzing issues, probably dc on the mains, not fully solved by a dc blocker and isolation transformer, voltage at 249v is also high.)

As to straight copper, I guess you mean copper strip, and may well be correct - I remember we used to use similar at the radio station, and it's often used for lightening conductors where I guess high frequencies (fast pulses) are likely to be an issue. Do you know of any good sources for such material - I probably need around 25m?

Cheers. Bill
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Unless you know the overall resistance of your main earth (on a TT system it could be as high as 200 ohms) upgrading your earth elsewhere will hardly make any difference overall.
 
Hi there Blackmetalboon

When last measured Ze (I think it is) was 15.07Ohm using the current spike - which as I mentioned I'm considering upgrading. This of course varies with the weather.

I assume the Ze figure is measured at dc (50Hz?) or at least close to it however, so probably doesn't say much about impedance to higher (noise) frequencies.

Cheers. Bill
 
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