Re: Re: Eureka
Yes. But what has asymmetry to do with anything being discussed?
se
myhrrhleine said:
Yes. But what has asymmetry to do with anything being discussed?
se
myhrrhleine said:
That presupposes there's directionality in the first place. Something which I've yet to see demonstrated.
se
PIM
Hi Bob,
Of course you can simulate phase shifts with great precision by means of an AC analysis. However, my point is what does it tell us about the amount of PIM. As far as I know, PIM is defined as the phase deviation/distortion as function of frequency and amplitude (correct me if I'm wrong). Doing an AC analysis, you will get phase shifts as function of frequency (of course) and the DC off-sett and at zero AC amplitude.
So far so good.
In my previous post (about this topic) I was moaning about precision, by which I mean how to translate phase modulation (due to DC off-set variation) obtained by AC analysis, into phase modulation obtained by transient analysis (due to amplitude variation). Not an an easy task, I guess. Do you know how to do that? I don't.
Then we have Pavel's simulation, that shows a shift of the zero-crossings (measured one per cycle!). Of course, a good amp should never show up this kind of behavior, but is it PIM? We don't know, as the same phenomenon might be caused by another kind of disturbance.
As pointed out in one of my previous posts, I suggest to look at the rising and falling ZC as well (i.e. two ZC's per cycle), as that might eliminate the effect (to some extent) of DC off-set, but still the outcome is also affected by the amount of even harmonics.
So, what to do? It depends on how you define PIM. If you define it as function of amplitude, then calculate the real phase by mens of a FFT (or a equivalent of that method). If you define it as function of DC off-set, just do an AC analysis. But in no case a single ZC measurement.
Cheers,
Edmond.
Bob Cordell said:
Hi Bob,
Of course you can simulate phase shifts with great precision by means of an AC analysis. However, my point is what does it tell us about the amount of PIM. As far as I know, PIM is defined as the phase deviation/distortion as function of frequency and amplitude (correct me if I'm wrong). Doing an AC analysis, you will get phase shifts as function of frequency (of course) and the DC off-sett and at zero AC amplitude.
So far so good.
In my previous post (about this topic) I was moaning about precision, by which I mean how to translate phase modulation (due to DC off-set variation) obtained by AC analysis, into phase modulation obtained by transient analysis (due to amplitude variation). Not an an easy task, I guess. Do you know how to do that? I don't.
Then we have Pavel's simulation, that shows a shift of the zero-crossings (measured one per cycle!). Of course, a good amp should never show up this kind of behavior, but is it PIM? We don't know, as the same phenomenon might be caused by another kind of disturbance.
As pointed out in one of my previous posts, I suggest to look at the rising and falling ZC as well (i.e. two ZC's per cycle), as that might eliminate the effect (to some extent) of DC off-set, but still the outcome is also affected by the amount of even harmonics.
So, what to do? It depends on how you define PIM. If you define it as function of amplitude, then calculate the real phase by mens of a FFT (or a equivalent of that method). If you define it as function of DC off-set, just do an AC analysis. But in no case a single ZC measurement.
Cheers,
Edmond.
Re: Re: Eureka
But still going hence and forth, making the mean (=DC level) is zero. 😀
What's your point angle? 🙂
myhrrhleine said:
But still going hence and forth, making the mean (=DC level) is zero. 😀
What's your point angle? 🙂
myhrrhleine said:
I wonder what in the manufacturing of the wire could possibly introduce directionality. I think the annealing would eliminate any influence the drawing process had or ever could have.
Oops, this is a preamp thread.
Cal Weldon said:
Presuming there is directionality.
What's the point of speculating on the cause of something which hasn't even been conclusively demonstrated to exist in the first place?
It's rather like speculating about which hand Big Foot uses to wipe his bottom.
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Cable Directionality
FWIW, Supra Cable claim to have found a measurement technique (undisclosed, to my knowledge) to identify cable directionalty, look at a the last pages of their catalog. Unfortunately their reasoning in the text seems a bit strange to me.
I personally like this text, Conduction In Metals, by Mr. Renardson much better, as it fits my experiences so far (that is, "non-event" of directionality).
- Klaus
FWIW, Supra Cable claim to have found a measurement technique (undisclosed, to my knowledge) to identify cable directionalty, look at a the last pages of their catalog. Unfortunately their reasoning in the text seems a bit strange to me.
I personally like this text, Conduction In Metals, by Mr. Renardson much better, as it fits my experiences so far (that is, "non-event" of directionality).
- Klaus
john curl said:
Yeah. Sure you do.
Hate to be the one to tell you, BUT there are diodes in your metal wires. More than you will ever bother to measure. I have measured them. --John Curl
Or how 'bout this one?
I have some 'old' Jensen spec sheets around here. I just don't have them in front of me. YOU, Steve Eddy, are the dupe, the fool, the shill for them. I mean to tell you this as a colleague,(and to get you off my ankle). I KNOW what I have seen with my own eyes, and watched it be buried over, in the following decades. --John Curl
Shall I go on?
se
Re: Cable Directionality
Well sure. As long as they don't disclose the supposed measurement technique, no one can independently verify or falsify it. So they can make any claim they want.
Brilliant, isn't it?
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KSTR said:
Well sure. As long as they don't disclose the supposed measurement technique, no one can independently verify or falsify it. So they can make any claim they want.
Brilliant, isn't it?
se
Edmond Stuart said:
Hey Glen, finally you got it!
Load the VAS output as much as you can (using only sonical approved resistors, of course) and you will get a very high corner frequency of the open loop gain. And please, no whining and moaning about the added distortion, as the golden ears are totally immune for such trivial artifacts.
Cheers,
Edmond.
😀 😀
Hey guys,
Now this is a cable thread? All right, I'll bite.
Talking about cable directionality, true or not, is a complete waste of time. And now I'll keep you believers up at night, sweating beneath your sheets.
What about all the miles of untested studio cabling?
How about the thousands of iffy switch contacts in those mixing consoles and outboard gear?
How ..... about .... absolute .... phase ????
The way I see it, some of you are like dogs chasing your tails. Some of these alleged effects are studied so closely under a microscope that you can't see the big picture. So much pointless discussions and arguments over things that are beyond your control.
A question then. Is it possible for a cable to reverse it's directionality? Now that would be hilarious!
John. Do you want to talk about real circuits and what concepts you found important enough to include in the design of this preamp? I mean, this was a thread pertaining to one of your very successful products. I would think that you would like to make your time worthwhile here. It's up to you, what are you going to do?
-Chris
Now this is a cable thread? All right, I'll bite.
Talking about cable directionality, true or not, is a complete waste of time. And now I'll keep you believers up at night, sweating beneath your sheets.
What about all the miles of untested studio cabling?
How about the thousands of iffy switch contacts in those mixing consoles and outboard gear?How ..... about .... absolute .... phase ????
The way I see it, some of you are like dogs chasing your tails. Some of these alleged effects are studied so closely under a microscope that you can't see the big picture. So much pointless discussions and arguments over things that are beyond your control.
A question then. Is it possible for a cable to reverse it's directionality? Now that would be hilarious!
John. Do you want to talk about real circuits and what concepts you found important enough to include in the design of this preamp? I mean, this was a thread pertaining to one of your very successful products. I would think that you would like to make your time worthwhile here. It's up to you, what are you going to do?
-Chris
myhrrhleine said:
Excellent point! Taking the proposed mechanism, I would think each length of wire is "directional" due to haveing a little more copper/copper oxide rectification in one direction due to averaging a random distribution. Therefore each length has a random chance of being an inny or an outty. Same goes for impedance variations a random distribution around an average.
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