A thread for discussing the science behind power cables and their potential influence on amplifiers
- Thread starter Whaleblue
- Start date
misterdog
Not the canine kind
The 'patent' providing evidence to those contemplating a purchase that it must be a worthwhile 'investment'.
Almost as if science approves it.
Marketing bullshit, yet people flock to it, you might think that the world would have become accustomed to such.
If Carlsberg made mains cables
Audiophiles would all be happy, but GDP would plummet.
Jim Audiomisc
pfm Member
AIUI his theory is that changing one mains cable for another alters the hum/buzz level/details emerging and being sent out to the loudspeaker. That then makes an audible difference.
Such a theory fits with my experience that low levels of hum/buzz/etc sometimes pass un-noticed in themselves, but can then alter what we hear when we play music at the same time.
However his theory is quite testable because we can measure the details of the hum/buzz at the power amp output terminals and see if any changes occur when te mains cable is changed. Then also see if this correlates with people saying (or not) that the result sounds different.
So has anyone done this?
John Phillips
pfm Member
And in particular I think the text
"Since the ground is connected to the components' case, as is usually […] the earth wire on the power cord, the most basic rule of signal transfer through standard unbalanced interconnect cables is violated - the forward and return currents must always be exactly equal. Instead, if you look at the actual situation, the forward current travels through a wire connecting RCA central contacts, while the return current travels through the wire connecting the outer (ground) contact AND EVERY EARTH WIRE in the system in all possible combinations."
hypothesises that mains ground currents (possibly dependent on power cords) can flow in the signal return paths of interconnect cables. This will add low-level interference from the mains that may be audible if the resistance of the return path is great enough. FWIW I agree that this hypothesis is very reasonable and I am sure it does occur. However it is, I think, not inevitable. For example:
1. When using unbalanced coaxial RCA interconnects (one inner "hot" conductor and screen as "return") select interconnects where the resistance of the screen is as low as possible. Proper copper braid and not metallised Mylar wrap with a drain wire.
2. Use "pseudo-balanced" RCA cables with twisted-pair inner conductors for hot and return, which just connect the screen at one end to the return wire so the screen no longer carries any earth current.
3. If possible, use equipment where signal ground and safety ground are connected more thoughtfully to minimise or eliminate interfering ground currents and/or use XLR balanced interconnects.
It would be interesting, indeed.
Jim Audiomisc
pfm Member
FWIW I've been aware for many decades of the potential (pun!) problems with grounding. But in my case this started with ultra-low-level signal detection using receivers on telescopes up on a mountain/volcano! And in some cases where static was also a problem and/or there were > 2kV Power supplies to the receiver. Compared to this, audio seemed less of a problem.
But to me, for home systems it seemed to boil down to some fairly basic requirements. Get the grounding arrangement right and avoid loops or ground currents that generated pds in the signal path. Ensure the kit was designed well enough not to create its own problems. Agree with your comments. Which makes me wonder if when people find the mains cables make an audible difference they should be looking more at their amps, etc, than at the cables as being the fly in the butter.
I have, however, in the past been surprised to find some interconnects that at first glance were coax but when cut open simply had two parallel wires. OK, gives low capacitance, but not a good idea IMHO.
Add to the above my continued low-level curiosity about the way no-one these days seems to check on ripple being injected via the power rails and intermodulating with the signal as well as cropping up at LF in the output. This won't show up on TDH measurements but if it happens may be much more noticable.
But to me, for home systems it seemed to boil down to some fairly basic requirements. Get the grounding arrangement right and avoid loops or ground currents that generated pds in the signal path. Ensure the kit was designed well enough not to create its own problems. Agree with your comments. Which makes me wonder if when people find the mains cables make an audible difference they should be looking more at their amps, etc, than at the cables as being the fly in the butter.
I have, however, in the past been surprised to find some interconnects that at first glance were coax but when cut open simply had two parallel wires. OK, gives low capacitance, but not a good idea IMHO.
Add to the above my continued low-level curiosity about the way no-one these days seems to check on ripple being injected via the power rails and intermodulating with the signal as well as cropping up at LF in the output. This won't show up on TDH measurements but if it happens may be much more noticable.
S-Man
StrivingON
Some good points Jim & John.
Many people have expressed the view " how can the last metre of wire make any difference when the power has been transmitted for miles down lots of cables". Hopefully they can now see that only considering the supply impedance is mostly missing the point!
Many people have expressed the view " how can the last metre of wire make any difference when the power has been transmitted for miles down lots of cables". Hopefully they can now see that only considering the supply impedance is mostly missing the point!
AndrewM
pfm Member
Yes, looked at this way, you can say that the last metre of wire on two components, as you put it, could be forming the twin legs of a ground loop. Unusually for a cables thread, this discussion has actually taken an interesting turn, and I actually feel I have learnt something new about how grounding issues and connections could be making a difference (without invoking quantum theory!) Thanks everyone.
Omg. Ark less is spot on. You have audiophile fantasy from people who are totally ignorant of electrical and electronic engineering V people who are trained, educated and experienced in the subject. He certainly speaks for this engineer and I know who I think is arrogant in this scenereo and its not Arkless.
The quantity of snake oil products out there clearly demonstrate that there is no reason whatsoever to trust audio designers. These companies are there to sell product, high profit margin mains cables is an easy sell to the technically ignorant.
Zero trolling in his comments, more censorship than moderation Tony.
OK, if you believe your equipment is affected by the mains cable, perhaps you should consider what a poor design it is to suffer this problem. Mains conditions will vary - guaranteed. it should be within a products design to be tolerant if the variations, ie proper psu and product design.
Or do you think its a virtue to be intolerant of mains conditions¿
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S-Man
StrivingON
And yet there are other engineers e.g. Jim, John and the ilimzm (on DIYAUDIO) who do suggest there may be reasons why mains cables can affect the signal integrity. Maybe you need to read the last few posts?
Arkless does appear to be a decent engineer, but his (repeatedly ranty) view on this topic is most likely too simplistic.
cooky1257
pfm Member
Hmm so, AIUI, any normal ie unbalanced system that consists of several components hooked up to an amp will/can have particular earthing arrangements that can compromise the isolation from mains-born interference. What I don't understand is how only one special mains lead to power just one of these components can improve the whole system ie isn't the compromised earthing arrangement still undoing the 'benefits' from the new mains lead via the other paths to the mains?
S-Man
StrivingON
It's not just mains-borne interference.
Signal corruption can be caused by magnetic, electrostatic and inductive coupling... the equipment power transformer often being problematical.
Of course it's all a question of degree. A really bad system will cause hum with no signal, a non-ideal system might have no hum but have signal related modulation (that is (mostly) hidden by the music.
Since "one special mains lead" is part of this complex sytem of interactions, it could change the coupling. We are talking tiny, but possibly audible, effects here.
IMO spending a lot of money on a random chance of fixing a system problem is stupid. The solution does not need to expensive... just properly thought out.
Signal corruption can be caused by magnetic, electrostatic and inductive coupling... the equipment power transformer often being problematical.
Of course it's all a question of degree. A really bad system will cause hum with no signal, a non-ideal system might have no hum but have signal related modulation (that is (mostly) hidden by the music.
Since "one special mains lead" is part of this complex sytem of interactions, it could change the coupling. We are talking tiny, but possibly audible, effects here.
IMO spending a lot of money on a random chance of fixing a system problem is stupid. The solution does not need to expensive... just properly thought out.
May be reasons?
Mains conditions can affect product performance, RF, voltage fluctuations. The last metre of cable is totally ineffective at dealing with those issues.
Proper psu and product design is.
You are being conned pure and simple. It's audiophile technical ignorance and marketing bullshit that allows this stuff to persist.
Arkless view isn't simplistic, it's informed.
S-Man
StrivingON
No PSU is perfect and even then you still have to connect the PSU to the load and decoupling in the most appropriate way. Then you have to connect the thing containing a PSU to other things containing PSUs...
..... But of course those imperfections are dealt with by a mains lead..........
can you go into a specific example of a psu imperfection and how it is corrected by a mains lead?
John Phillips
pfm Member
Yes, it is quite difficult to see many situations where changing one mains lead (keeping it plugged into the same socket) can have a significant effect. It's easier to see how swapping a poor interconnect cable (e.g. with screening having excessive resistance) might transfer less mains noise into a low level signal now that we regularly have very high dynamic range sources.
There are too many design and configuration unknowns to see the effects clearly and I have no idea how common any of the effects discussed here may happen.
AndrewM
pfm Member
You seem to have jumped into this discussion rather aggressively. I tend to agree with you that fancy mains cables are generally ineffective and are more about marketing and profit than anything else. But I am interested in the considerable volume of anecdotal evidence that quite a few people do hear differences between different mains cables, and I think it is a bit lazy simply to attribute that all to placebo effects. I therefore am open to suggestion that where amplifier design is less than perfect, swapping a cable with one with slightly different electrical characteristics might make a difference. But that is not to say that I am in anyway promoting or encouraging the purchase of expensive cables, and I agree that the real solution to any mains problem is better design in the first place...... But of course those imperfections are dealt with by a mains lead..........
can you go into a specific example of a psu imperfection and how it is corrected by a mains lead?
Here is a hint. Take a look at an area I'm familiar with, Keysight test and measurement equipment. Some very high end, SOA measurement kit there, spectrum analysers, pico a meters, electrometers stuff measuring electrical quantities and parameters an order of magnitude more subtle than anything your hifi is doing......... Not a funky mains lead in sight. Bog standard IEC leads.
Yep cos it's the same old cyclic total bollocks that keeps going round.
Why are you taking anecdotal uninformed, biased, uncontrolled and sometimes delusional audiophile commentary seriously? Plenty of people believe in God, doesnt make it any more real. Anecdotes are not evidence. Anecdotes are not fact. Simply a personal view. If that view is uninformed, biased or based on uncontrolled information, what is it worth?
Being open minded is one thing, allowing your brain to fall out is another. Being informed is far more effective.
The risk of being open minded, if you know nothing about a subject, is that you can be led into believing anything. That's the whole purpose of the snake oil marketing and why its effective. Pseudo science that is plausible to the uninformed. Unfortunately audiophiles seem particularly susceptible, sometimes even anti knowledge.
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One particularly comical bit of mains cable marketing I saw a while back (can't remember who) was talking about this amazing test rig they had developed to measure the transient current that could flow through their leads. You know thousands of amps. With the implication that this is required to allow your amp to follow the musical transients.
If you actually measure the mains current flowing into an amp what do you see? Not the musical transients. A low level of cyclic current of the psu resevoir caps charging. I will try and dig out a plot of this.
If you actually measure the mains current flowing into an amp what do you see? Not the musical transients. A low level of cyclic current of the psu resevoir caps charging. I will try and dig out a plot of this.