Logo Computer scientist,
engineer, and educator
• Articles • Articles about science and technology

Snake oil: hi-fi mains cables

Snake-oil Sam's target today is: hi-fi mains cables. You'll probably know by now that if you want the best possible sound from your hi-fi system, you'll need to invest in loudspeaker cables made from oxygen-free copper, unidirectional signal interconnects (because electrons flow more easily one way than the other), top-of-the-range optical-fibre audio connections (because, let's face, some 1's and 0's are better than others), and a whole range of other zippy goodies. At last, the snake-oil salesmen have started to target the one part of the system that has so far been overlooked — your mains cable.

Now, you thought that a mains cable was a mains cable, right? So long as it's thick enough to carry the current, and doesn't electrocute anyone, that should do. But no: the mains cable is now the central part of your hi-fi system! Save a few quid here, and all the other expenditure will have been for nothing. In fact, nothing short of oxygen-free copper (here we go again), thick enough to carry about 500 amps, will do for the most discerning listener. If you get the right mains cable, you'll experience ear-tingling high-frequency definition, deep, resonant bass, and a load of other stuff that the hi-fi snake oil folks like to spout. And the price? £200-1000. That's right — your could pay a grand for a mains cable. In a way, the very worst thing about this scam is that if you are barmy enough to spend several hundred pounds on a mains lead, it will be so thick and heavy as to be almost unusable.

Anybody who has been swayed towards the opinion that 'audiophile mains cables' are a worthwhile investment, should perhaps bear in mind the following facts.

1. The music you listen to will probably have been created in a recording studio. Even if it hasn't — it's a live performance perhaps — by definition it will have been recorded using electrical equipment of some sort. This equipment will have been mains powered. Now, I've spent time in recording studios, and I can't say that I ever saw one that used 'audiophile mains cable' to power its mixing and amplification equipment. In fact, I've seen mains leads scavenged from kettles and toasters to power the mixing desk. As a matter of principle, your sound reproduction can never be any more accurate than the original recording. So if you spend more on your cables (mains or otherwise) than the studio does, you're wasting your money.

2. Modern, decent-quality amplifiers do draw a heavy current load, particularly on transients like drum beats. They generally have great big capacitors internally to make up this transient current, and the mains supply only has to meet the average current demand. Even if the capacitors aren't doing their job, using better mains cable isn't going to help. Why not? Well, mains cable has no ability to store and dish out current on its own — if it did, a fuse would blow every time you plugged in. The only way you can increase the current that is supplied to your amplifier is to reduce the electrical resistance between the electrical power source and your amplifier. Now, the power source can usefully be taken as the big grey transformer that steps down the grid voltage to ordinary mains voltage — there's usually one of these in each neighbourhood, and your house will be perhaps 100-1000 metres from it. Add to this distance the length of electrical wiring in your house, and you can see that even if the mains cable were so thick that it were effectively of zero length, it will have negligible effect on the overall electrical resistance.

3. The manufacturers of hi-fi mains cables claim that their cables introduce less noise into the amplifier's power supply than inferior cables. It is presupposed that reducing the noise on the power supply input will reduce the noise on the low-voltage DC it generates, and that this will reduce the noise impressed on the amplifier output. Both these suppositions are questionable but, even if we accept them, it remains the case that mains cables contribute negligible noise to the power supply. Even if you screen your mains lead to reduce electromagnetic pickup, you probably haven't screened the rest of the wiring in your house, or in the street. And, although a low-resistance cable does (as a matter of physics) generate less thermal noise than a high-resistance cable, no reasonable cable is going to generate more than a few picovolts of noise of this type.

In short, if you want to spend money on your hi-fi system, the cost of 'audiophile' mains cables would be far better spent on, say, better loudspeakers.

Copyright © 1994-2013 Kevin Boone. Updated May 14 2010