Lost all respect for Doug Self

[617]

As long as we're being pedantic you hopefully didn't lose 'all' respect for Doug Self. Of course arguing on the internet is never strong evidence of Self respect.

 

[amirm]

Easily shown doing time domain reflectometry even with a scope. I am totally being pedantic, but how can we be respected as technical experts when we can't prosletytize wrong statements. Cables are much more complex than simple LCR networks.

Do you have such measurements or are speaking from theory? If you have them, let's see them so we have some idea of what we are talking about.

 

[Raindog123]

An audio cable as a passive two-port network, if badly designed, may represent itself a non-reciprocal linear network, which may attenuate certain frequencies on one direction more than on the other.

This does not violate the superposition theorem in either direction. Cables marked with directionality arrow, must have some added passive components at one of the terminal ends.

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

 

[617]

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

Dibs on coauthorship

 

[audio2design]

Is there really this level of lack of understanding. Cables are real physical things. Superposition and reciprocity assume perfect conditions. They are theoretical constructs useful for simplification of analysis. They assume no time delay. Cables have time delay. By even bringing these up you are already assuming symmetry. You can't use symmetry to prove symmetry. Time for a bunch of you to go back in the lab.

Let's simplify even more. Are you telling me a simple circuit that is a 10R resistor into a 1uf capacitor (RC filter) with a 1 ohm resistor to the output has the same transfer function in each direction? Obviously it does not. That is the real world. That is cables. They are not perfectly symmetrical. That is not even getting into very real transmission line effects that are also directional.

 

[HiFidFan]

Imagine a cable. It is two simple conductors. The total cable is 1 meter long. The two conductors start 0.1 meters apart at each end. They almost touch at 0.8 meters, but by 1 meter they are again 0.1 meters apart. That cable will not behave the same in either direction except at DC.

And this behavioral difference you claim, is it audible?

 

[Raindog123]

Let's simplify even more. Are you telling me a simple circuit that is a 10R resistor into a 1uf capacitor (RC filter) with a 1 ohm resistor to the output has the same transfer function in each direction? Obviously it does not.

Absolutely it is. The principle does not require symmetry, not at all.

Let me put it in as clear terms as I can....

 

[audio2design]

The one looking foolish for being up Lorentz reciprocity is not me. Again you are using symmetry to prove symmetry. Circular argument. May want to read what Lorentz reciprocity is in more detail.


Now how about you explain how Lorentz reciprocity works 1 nanosecond after I apply a voltage pulse to a 100 meter long cable. Current is not the same everywhere is it?

 

[audio2design]

And this behavioral difference you claim, is it audible?

Never claimed it was. Even said it was not. Not the issue. It is about whether AC removes the potential for a cable to be directional.

 

[HiFidFan]

Never claimed it was. Even said it was not. Not the issue. It is about whether AC removes the potential for a cable to be directional.

Got it.

 

[audio2design]

And this behavioral difference you claim, is it audible?

Let me put it in as clear terms as I can....

View attachment 126101

Your ignorance does not change reality. I get it. I moved your cheese.

 

[Chrispy]

Never claimed it was. Even said it was not. Not the issue. It is about whether AC removes the potential for a cable to be directional.

So it's theoretically at a miniscule value "directional". How does this matter?

 

[audio2design]

So it's theoretically at a miniscule value "directional". How does this matter?

Because we hold ourselves up to be the arbitrars of the truth. How does that work when we make statements that are not, even at the most fundamental level, defensible.

 

[Beave]

Still wondering at what frequency this starts to be an issue with real world cables?

Not kHz, for sure.

MHz? Nah.

GHz?

 

[audio2design]

So it's theoretically at a miniscule value "directional". How does this matter?

At very high frequencies it actually matters a lot. Very high frequency cables must be tightly controlled in manufacturing and use dielectrics that are mechanically stable.

 

[MZKM]

The exception to this would be in the case of shielding in a balanced cable being connected at only one end.

I would like Amir to do a test on how well these cables do or do not work. But first would need some external way to introduce noise (I assume these are for EMI/RF, and not noise from the source).

 

[audio2design]

Still wondering at what frequency this starts to be an issue with real world cables?

Not kHz, for sure.

MHz? Nah.

GHz?

It is always true. The statemt that cables are not directional because of AC is WRONG. They are directional because of AC. Whether practically that matters for a particular application is a different question.

 

[audio2design]

I would like Amir to do a test on how well these cables do or do not work. But first would need some external way to introduce noise (I assume these are for EMI/RF, and not noise from the source).

Connecting or not connecting a shield (and where) can make a big enough difference in effective capacitance to change the frequency response in an MM cartridge. Get a high output impedance tube stage and the difference is enough for a measurable but likely inaudible difference in frequency response.

 

[Ron Texas]

I can't believe this.

 

[tomchr]

It's not just for audio. RF cables aren't directional either. A waveguide for the RADAR bands isn't directional ether. Superposition is a thing.

OP may want to consider that the L, C, and R in the LCR model are distributed components, not lumped ones.

Tom