speaker cable myths and facts

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Just looked at that post - the telling thing was that the cable was 'proper' cable, taken from serious RF equipment - where it obviously hadn't caused a significant issue for the operation of that unit.

Unfortunately the conventional, theoretical reasoning about why these effects should not be audible, as expressed in the last page or so here, doesn't bear out. The effect is audible, I can hear it, if I ignore it the degradation remains until I do something about it. Now, I'm as interested as anyone else as to why it occurs, but I haven't found anything seriously explorative of the behaviour in the literature - it's generally the same repetition, of the same basic concepts, almost boilerplated from one piece to the next.

Trouble is, it's real will o' the wisp behaviour, most people just want it to go away, so the real focus is on just stopping it, rather than precisely analysing how it may impact in some non-obvious manner ...
 
SY, I still have some questions regarding microphonics due to triboelectric
effects in PTFE / silver cables:

From the link you have posted it appears that you observered a microphonic
effect on specifically _one_ make of cable which happend to be PTFE / silver.
How did you verify that this was due to a triboelectric effect ?
Did you test other PTFE / silver cables, so you can conclude all PTFE / silver are that way ?

Bedea (a well reputed manufacturer, not a "boutique" brand) makes some
low noise cables:

Low noise coaxial cables

some of them actually use PTFE and copper braid silver plated shielding:

LN5002 LowNoise coaxial cable - coaxial line: koax24
 
Did some Google searches meanwhile and there seems to be no general
consensus about this, sometimes even the same person seems to disagree
with himself:

Bruno Putzeys about microphone cables (2004):
Cable Distortion and Dielectric Biasing Debunked | Audioholics
"To make matters worse, teflon and silver are about the worst thinkable combination in terms of triboelecticity."

Bruno Putzeys 4 years later:
A Microphonic Wire?
"I don't agree that PTFE/Silver Plated cable is bad for microphony. ...
Furthermore, PTFE is very stiff so it produces a relatively high mechanical Q. I've tested a lot of cable for microphonics and teflon cables were simply in a leage of their own."

Seems a to be a confusing issue ...
 
I missed it, what is it you're hearing?

I hear any tapping, sliding, vibration... things acted like a perfectly microphonic circuit (which is what I thought it was until belatedly replacing the shielded cable and having the microphonics disappear). If I were a bit of a snake, I would have built this into a cabinet and sold it to some gullible audiophile with a rap about the "bloom" and "liveliness."

Did you test other PTFE / silver cables, so you can conclude all PTFE / silver are that way ?

No, and I wouldn't claim that. That kind of shielded cable is expensive and unnecessary, so I wasn't going to buy more- it's more effective to avoid it in the first place by using other, cheaper dielectrics and wire materials which are less susceptible to triboelectric effects. Yes, I could spend a pile and get a PTFE/silver cable where pains have been taken to eliminate those effects and get something which performs identically to PVC/tinned copper at only 20 times the price. The advantage to PTFE in audio frequency circuits is temperature range, which isn't really relevant.

"Free" was a big attraction for that particular coax. And it was worth every penny. 😀
 
Bruno Putzeys 4 years later:
A Microphonic Wire?
"I don't agree that PTFE/Silver Plated cable is bad for microphony. ...
Furthermore, PTFE is very stiff so it produces a relatively high mechanical Q. I've tested a lot of cable for microphonics and teflon cables were simply in a leage of their own."

Seems a to be a confusing issue ...

No, I think you've garbled the quote. Bruno was still criticizing PTFE/silver for exactly the same reasons he did earlier (and completely consistent with my experience). The first sentence was his quoting of someone with whom he disagreed.
 
Georg,

I would still use that nice cable and check if you can replicate SY's findings. If not, you are good to go. I use small dia coax teflon/silver coated because of the ease of soldering in tiny quarters, never had problems as described by others. We shouldn't over-exaggerate this tribo-electric phenomenom.
 
OK, so there's 25k source impedance in parallel with 220k load impedance, so call it 22k. Accepting Dave's guesstimate (I am somewhat skeptical of it- I think you have to look at charge generated vs discharge time) of 10s of nA, that's 0.2mV. I think that's too low, but I only had a sample of one (times two channels, of course), set up differently, and no time to pursue or quantify it.
 
Georg,

I would still use that nice cable and check if you can replicate SY's findings. If not, you are good to go. I use small dia coax teflon/silver coated because of the ease of soldering in tiny quarters, never had problems as described by others. We shouldn't over-exaggerate this tribo-electric phenomenom.
This was what I was originally asking anyway: how the answer was attributed to discharge within the cable. Every single thing in the world is vibrating and moving somewhat 100% of the time. You do have to cross a threshold, however, to strip off free charges. You have to once again do this enough times to build up a meaningful potential, and I'm still not convinced that this is possible in any form of audio cable. Unless you're creating an electric field at the ends of a cable rather than along its length, I still don't see how it's possible to attribute microphonics to minute amounts of static buildup.
 
Charges are created by triboelectricity- that's just plain well-known physics. They will discharge according to basic E&M- again, just plain well-known physics. The discharge is a transient signal, ditto. PTFE and silver are a combination particularly prone to triboelectric charging, ditto. You do not need a difference in the field along the cable, and in fact, when transmitting desired signal, there's no significant field along the cable- the triobo charges discharge across the Thevenin equivalent resistance of source and load in parallel, producing a spurious input voltage which is amplified by succeeding stages, ditto.

Now if you have a better explanation of this cable microphony which goes away when switching to PVC/copper, and it's based on physics, I'm all ears.
 
lemans23 said:
I believe you did. No one had mentioned it until you said some cable had 10nA of "tribo current".
I was correcting a calculation based on an estimate made by fas42. He forgot that the dominant relevant impedance is the source, not the load.

There is no such thing as triboelectric current, only charge, and discharge.
I am curious. How does charge move (to charge and discharge) without there being a current?

SY said:
Accepting Dave's guesstimate
Not mine. I was merely correcting someone else's calculation from that estimate. I have no idea how plausible the current estimate is.
 
When SY gets the cable to me, we may find out. 🙂 Should be fun.

FWIW, I've tested a Noble 50K log pot with 9V DC across it and could get no microphonic effect at all going into a sound card. Will test again, just to be sure.
 
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