Power Cables. Are they overhyped? Part III

[Julf]

I think thumping may not be the correct test.
I can only speak from my experience here, but I had an example of microphonics in action.

Microphonics are an issue, but only at very low signal levels (so mic cables, inputs and preamp stages). A power cable has voltage and current levels (and a low impedance) that completely drowns out any microphonics.

 

[neil]

This all seems very sensible as far as it goes, but the point at issue is much simpler than that-
1. if and to that extent that the explanation for "sounds different" reports is some physical effect operating through sound pressure waves only, not the ordinary operation of multi-sensory integration, subconscious cognitive processing and/or a tendency to project minutiae of one's experience to hifi kit......
2 and that effect is down to rf filtering in the mains cable (more plausible assuming 1, but that's a big assumption) then
3 then using a mains cable rather than an rf filter would be a dumb (unreliable partial) way of achieving this effect. Correct solution costs a few quid. not millions. less than even a cheap aftermarket mains cable. [this point applies either in the mains cable powered device or by way of aftermarket add on]
4. hierarchies of mains cables would particularly make zero sense (see Russ Andrews graphs comparing the various levels of pointless lowgrade-rf-filtering mains cables )

however
1. if but only if I take as my starting point "I hear differences in mains cables"
2. and I will only believe that I am not detecting a difference in the sound pressure waves if you prove to me to my satisfaction beyond any doubt reasonable or otherwise that it it not possible for such an effect to be caused by the physical properties so the mains cable
3. then my mains cable is an rf filter sounds plausible, that'll do for me.
but
4. and I am not interested in really thinking whether this makes sense, I just want to go back to thinking what an amazing measurement device my ears are. Pass me the next mains cable.

The point at issue I was referring to was BE making an absolutist assertion that he claimed as fact.

WRT the op for the thread I have not commented within this thread. My views are influenced by several factors including my electrical and electronic engineering degree, 25 years working on government research in a variety of areas, personal experience and my views as to the purpose of a hifi system in a domestic setting (which may not align with many other people's).

 

[neil]

Microphonics are an issue, but only at very low signal levels (so mic cables, inputs and preamp stages). A power cable has voltage and current levels (and a low impedance) that completely drowns out any microphonics.

If I understand Venton correctly he is not arguing that the power cable itself is microphonic but that it may transmit mechanical energy to the circuit boards and thereby to components on them that may themselves be microphonic and that are carrying lower level signals.

 

[Ted-M]

I'm already looking forward to part IV of this!

 

[Lee T]

Three groups of people with regard to one of these amps that some members have identified as benefiting from a change of mains cable.

A Change mains cables and hear a difference in the amps sound
B Change mains cables and hear no difference in the amps sound
C What are they on about (vast proportion of the global population)

For A the amp is faulty, B not faulty, C where did you go for your holidays.

If you like talking about how mains cables change your world pop into http://theaudiostandard.net/thread/3053/mains-cables-hear nobody seems to have accepted his offer to demonstrate yet but they are talking the idea up.

The title should be amended to "Mains cable prices, are they overhyped" in most cases, it would be a resounding yes.
This to me is what is at the core of any mains cable debate, the cables themselves can be had for peanuts if you do your homework, so no need to be a rip off for anyone.

This will just be another overblown thread about the usual, how tedious.

The faulty amp cop out clause is also ludicrous as an excuse.

Unless those who claim this have examined the amps involved, tested them & measured them, it's nothing more than hearsay & trolling.

Out of interest, did you blind test your cable with a group of people or did you know the cable was in place, you still havn't answered this question from weeks ago.
Same goes for the regenerator, I would imagine, if the regen improves matters, any amp your using is also faulty...right?

 

[adamdea]

The point at issue I was referring to was BE making an absolutist assertion that he claimed as fact.

WRT the op for the thread I have not commented within this thread. My views are influenced by several factors including my electrical and electronic engineering degree, 25 years working on government research in a variety of areas, personal experience and my views as to the purpose of a hifi system in a domestic setting (which may not align with many other people's).

Ok. I see the distinction. Nevertheless, adjusting BE's perhaps slightly bold generalisation doesn't really take us very far though does it? Assuming that some vintage kit might be susceptible to some forms of RF still doesn't make mains cables into a sensible form of RF filter for use with them.

I'm intrigued by the idea of your having unusual views about the use of a hifi system in a domestic context. I sometimes put a cup of tea on my speakers -that sort of thing?

 

[Sue Pertwee-Tyr]

A quick question for Jim, or perhaps Julf:

What effect does adding an RFI filter to a mains lead have on the 60Hz mains waveform itself? Is there any measurable change to the mains waveform due to the filter still having (albeit miniscule) effects at non-RFI frequencies?

 

[Julf]

A quick question for Jim, or perhaps Julf:

What effect does adding an RFI filter to a mains lead have on the 60Hz mains waveform itself? Is there any measurable change to the mains waveform due to the filter still having (albeit miniscule) effects at non-RFI frequencies?

On the pure 60 Hz sine wave - no effect. The minuscule effect would be a minuscule attenuation of the whole wave - much, much smaller than the normal variations in the mains voltage. Of course if you have harmonic distortion on the mains, the harmonics will be attenuated more than the fundamental frequency.

 

[Julf]

If I understand Venton correctly he is not arguing that the power cable itself is microphonic but that it may transmit mechanical energy to the circuit boards and thereby to components on them that may themselves be microphonic and that are carrying lower level signals.

Ah, OK! Thanks for that explanation. So based on that, soft, flexible rubber mains cables would be better than stiff plastic ones (and all kinds of extra shielding etc. would actually make the situation worse).

 

[Jim Audiomisc]

I think thumping may not be the correct test.
I can only speak from my experience here, but I had an example of microphonics in action. I noticed by accident that my Naim 72 preamp case would 'ring' if I tapped it.
I therefore damped it by putting bluetack at the back to couple the case to the body. It no longer rang.
Expecting an improvement, I heard the opposite, the sound had no life to it. Simply removing and replacing the damping a few times and the differences were clear.

The point of a 'thump' is simply that it will generate a larger vibration than you'll tend to get over the air. Beyond that, the objects don't really know where vibration is 'coming from'.

Key question for your description: Did you find that the 'ringing' you heard appeared on the *electronic* signa output of the amplifier? Or were you simply hearing - via the air - the box vibrating? Having various objects in the room that resonate will alter the sound. But may have nothing to do with any *EM* signal the cables are feeding into a box. Thus not be a matter of 'microphonics' but simply acoustic resonances, etc.

 

[Jim Audiomisc]

If I understand Venton correctly he is not arguing that the power cable itself is microphonic but that it may transmit mechanical energy to the circuit boards and thereby to components on them that may themselves be microphonic and that are carrying lower level signals.

That should the show up quite clearly on the output signal if you thumped the cable.

 

[Jim Audiomisc]

A quick question for Jim, or perhaps Julf:

What effect does adding an RFI filter to a mains lead have on the 60Hz mains waveform itself? Is there any measurable change to the mains waveform due to the filter still having (albeit miniscule) effects at non-RFI frequencies?

A standard RFI filter is unlikely to have much effect at such low frequencies. However - apart from series resistance - that will able be so for mains cables. This why you'd need a regenerator or a better amp/PSU for such low frequency' problems.

You *can* DIY filters that reduce the LF passband. FWIW I made up a mains distribution board many years ago where I used large ferrite rings and wound the L and N around two of them to make some fairly large inductances with high saturation levels. Then added a more standard RFI filter downstream of them. But this still won't do much at 50Hz or its low harmonics.

 

[adamdea]

If you are worried about vibration I would have thought it would be important to ensure that you don't play any music near your stereo.

 

[Jim Audiomisc]

I've seen it argued that one reason some people like valve amps is *because* the valves are microphonic and add a small amount of 'reverb' to the sound. No idea if this is a reason. But they do tend to be microphonic. Note that this word means generating an *electronic* output from being vibrated. Not the same as tapping something and hearing the *object* 'ring'.

 

[kabayiri]

If someone rings me when I am listening to some music, it does interfere with my enjoyment of the music.

To solve this I swapped my smartphone for a fancy mains cable. No annoying ringing from anyone now.

 

[Guest432]

I've seen it argued that one reason some people like valve amps is *because* the valves are microphonic and add a small amount of 'reverb' to the sound. No idea if this is a reason. But they do tend to be microphonic. Note that this word means generating an *electronic* output from being vibrated. Not the same as tapping something and hearing the *object* 'ring'.

WRT the mechanical vibration in mains cables I tried this about 2 weeks ago.

I had a Modwright LS100 and when using a GZ37 I had to leave the cover off. I noticed that the amp became extremely microphinic with the cover off. To the extent that just tapping the case with a fingernail resulted in the ringing being heard quite clearly through the speakers.

I tried tapping various shelves and other kit in the rack to see how how microphonic it was. When tapping the power cable I heard nothing at all, only tapping the IEC connector in the socket did it ring and that needed quite a hefty tap.

I use standard kettle lead type cables so doubt very much if mechanical vibration could be transferred to internal components.

 

[Jim Audiomisc]

If people want to get some idea of the RFI rejection behaviour of typical general purpose mains RFI filters then these links may help a bit.

http://www.bulgin.com/products/mains-filters.html takes you to Bulgin's main page on this.

http://www.bulgin.com/media/bulgin/data/Mains_filters.pdf gets you the relevant product catalogue. Note that the amounts of rejection here are *much* bigger for the better filters than the results shown for the RA cables, and reduce RFI at lower frequencies more effectively. If worried above higher frequencies add a clamp on ferrite over the lead near the mains inlet just before the filter.

There are many other suppliers and models, many of which would be better in one way or another. But these are the kinds of filters you can typically get for 10 - 20 quid or so.

 

[venton]

Key question for your description: Did you find that the 'ringing' you heard appeared on the *electronic* signal output of the amplifier? Or were you simply hearing - via the air - the box vibrating? Having various objects in the room that resonate will alter the sound. But may have nothing to do with any *EM* signal the cables are feeding into a box. Thus not be a matter of 'microphonics' but simply acoustic resonances, etc.

Can't honestly say for sure. I tend to listen very carefully to vocals in particular and these sounded flat when the box was damped. It is possible that the 'reverb' of the box was acoustically adding to the flavour of the sounds, like reverb.

What about hifi stands? Do people think they do nothing? The thinking behind them must be to eliminate vibration getting into the circuitry. I dare say a lot more people 'believe' in decent hifi stands than fancy cables? But if so, what are they supposed to be doing, and is the effect measurable?

 

[Julf]

What about hifi stands? Do people think they do nothing? The thinking behind them must be to eliminate vibration getting into the circuitry. I dare say a lot more people 'believe' in decent hifi stands than fancy cables? But if so, what are they supposed to be doing, and is the effect measurable?

That is what they are supposed to be doing - and some valves and capacitors can exhibit microphony, so there is a possibility that some physically sensitive analog gear might be susceptible. Not saying it is a real issue...

 

[Jim Audiomisc]

What about hifi stands? Do people think they do nothing? The thinking behind them must be to eliminate vibration getting into the circuitry. I dare say a lot more people 'believe' in decent hifi stands than fancy cables? But if so, what are they supposed to be doing, and is the effect measurable?

FWIW my main hifi sits on a 'hi fi stand' I bought from the London Co-Op in the early 1970s. Its a bit rickety. But so far as I can tell that only matters if it 'creaks' whilst I'm playing an LP. It shuggles a bit if I push it. Keep meaning to add some blocks to strengthen the joins. But been meaning to do that for mumble decades now...