Lost all respect for Doug Self

[KSTR]

@audio2design, while your observation is basically valid, you have to put it into perspective of things.

Yes it is true that a cable can have a different linear transfer function depending on direction, just as any other 4-pole network.

But, for all intents and purposes the effect is irrelevant as
(a) the "damage" is linear (amedable) and
(b) it is so incredibly small that it doesn't matter.

I can measure such things down to -160dB below signal and there is nothing to be found with cables (teaser here: https://www.audiosciencereview.com/...dible-with-music-signals-some-examples.20886/)
One would be very hard pressed to build a cable in the normal way cables are built that actually showed any directionality to amounts that would result in more than, say -120dB of frequency response variation (mag and phase) in the audio range, and that maybe also would sport a non-linear behavior, again in -120dB realms.

So, within context, the statement of Douglas Self is 100% correct and does not violate anything.

You are supporting the same fallacy that many Golden Ears are fooled with by manufacturers: Just find any phenomenon that is is real and correct and verifyablem then construct a case around it.... but is complete irrelevant in applied theory as well as in practise as the order of magnitude of the effect is way way below any sensible thresholds of hearing, we're talking about a distance of 60dB++ to those thresholds.

 

[sergeauckland]

So you are claiming that a cable is basically a capacitor in parallel to the source followed by an inductor with a resistance ?
When you reverse that cable it becomes an inductor with a series resistor that goes into the capacitance ?

No measurements to back it up. No references to research of cables in the GHz range that show this ? No directional markings on any BNC cables ?

Nah. For anything audio related and video related and even digital audio related there is no directionality in cables other than the direction in which you can see the print on the cable. Funnily enough that print direction in audio-land is often said to be the direction it should be used in.
Source side on the first letter side, load on the last letter side.

My viewpoint of DS is not changed at all because of this thread.

If DS treated the OP with the contempt he deserves, then my opinion of DS has improved further.

Idiots shouldn't be pandered to.

S

 

[solderdude]

In all fairness OP did state, with respect to the audibility of this:

Never claimed it was. Even said it was not. Not the issue

So OP agrees that for audio purposes (that includes digital audio ?) cables are not directional when it concerns any audible effects.
So... there is no audible difference when it comes to directional behavior in cables which could occur in the >GHz range when a cable or its connector has some differences that would be measurable but inconsequential for music enjoyment.

To OP that's the reason to loose respect for DS. I think OP is the only one on this planet that lost respect for DS based on this aspect alone.
Or was it that DS did not respect OP's opinion on this and that caused OP to loose respect for DS.

 

[EB1000]

If a passive network indeed can violate the Lorentz reciprocity, we're talking Nobel Prize material here.

Lorentz reciprocity? You do realize we're talking about audio cables, not antennas? The Lorentz reciprocity is a concept that applies to distributed systems, not a lumped system like an audio cable, in which non-reciprocity is defined as the variation in the transfer function of the cable, calculated from both ends (v2/v1 and v1/v2). A simple RC network is non-reciprocal, so one can claim that it's directional.

 

[EB1000]

@audio2design, while your observation is basically valid, you have to put it into perspective of things.

Yes it is true that a cable can have a different linear transfer function depending on direction, just as any other 4-pole network.

But, for all intents and purposes the effect is irrelevant as
(a) the "damage" is linear (amedable) and
(b) it is so incredibly small that it doesn't matter.

I can measure such things down to -160dB below signal and there is nothing to be found with cables (teaser here: https://www.audiosciencereview.com/...dible-with-music-signals-some-examples.20886/)
One would be very hard pressed to build a cable in the normal way cables are built that actually showed any directionality to amounts that would result in more than, say -120dB of frequency response variation (mag and phase) in the audio range, and that maybe also would sport a non-linear behavior, again in -120dB realms.

So, within context, the statement of Douglas Self is 100% correct and does not violate anything.

You are supporting the same fallacy that many Golden Ears are fooled with by manufacturers: Just find any phenomenon that is is real and correct and verifyablem then construct a case around it.... but is complete irrelevant in applied theory as well as in practise as the order of magnitude of the effect is way way below any sensible thresholds of hearing, we're talking about a distance of 60dB++ to those thresholds.

Tell that to this snake-oil 8000$ interconnect cable:

https://mitcables.com/product/2c3d-level-1-audio-interconnect/

(it has a passive filter in the middle and it's marked with directionality arrows and many warning not to swap the two ends... )

 

[pma]

Audio signals are AC. Cables cannot be directional any more than 2 + 2 can equal 5. Anyone prepared to believe this nonsense won't be capable of designing amplifiers, so there seems no point in further comment. (Doug Self)


Obviously in this post, Doug is saying the often repeated, but ridiculously incorrect statement that because audio signals are AC, that cables cannot be directional. Now for those with a half decent understanding of electronics and cables, you understand that a cable is essentially a network of resistors and inductors in series, with capacitors in parallel, with some parasitic additional inductance, resistance and capacitance. Since no cable is perfectly manufactured, those values will vary along the length of the cable, especially capacitance and inductance. Like any other two-port transfer function with capacitors and inductors, at AC frequencies, the input-output function is not the same as the output-input function, especially when source and load impedance is taken into account.

Douglas Self is a well respected amplifier designer and in this field he has done remarkable work which he has also published.

Regarding cables, we all know Maxwell equations and theory of propagation of signal as an electromagnetic field along the cable. This comes into account for signal wave lengths comparable with cable length. In audio, this plays a game only in case of EMI coupled HF fields into the cable and corresponding reflections. This may bring some stability issues in a combination of some amplifiers and long speaker cables.

The "directionality" as mentioned usually by reviewers and manufacturers is a plain nonsense. They usually speak about shielded cable with 2 or more wires when shielding is connected to "ground" at only one end, either at the source or at the receiver. This has nothing in common with "cable directionality".

 

[DonH56]

At 40 GHz even good cables can exhibit different S11 and S22 (return loss, impedance looking into each end) -- they are not perfectly symmetric. But the variance is usually negligible for any decent cable. At 20 kHz, and audio systems, asymmetry is so far below the audible threshold (and usually near the measurement threshold), I just can't see how it matters. There are a host of parameters I sweat over at RF/mW/mmW frequencies that I could care less about for audio cables.

The only time I've used a TDR on a audio cable outside a laboratory experiment was to locate a break in a long cable at a venue.

 

[mansr]

Someone has dug himself into a hole, methinks.

 

[AdamG]

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