I have run a set of loopback tests and have interesting results.
Comparing three runs of the same conditions enables pretty good cancellation, ie good record events matching.
Comparing Both Normal to Both Reversed gives lousy cancellation.
Comparing Left Normal/Right Reversed to Left Reversed/Right Normal gives really good cancellation.
I will also compare swapping L and R cable positions next round of tests.
There are still some latency issues as I had to closely time align each recording, this needs closer inspection.
These results repeat what I obtained a week ago, more in the next few days.
Dan.
Comparing three runs of the same conditions enables pretty good cancellation, ie good record events matching.
Comparing Both Normal to Both Reversed gives lousy cancellation.
Comparing Left Normal/Right Reversed to Left Reversed/Right Normal gives really good cancellation.
I will also compare swapping L and R cable positions next round of tests.
There are still some latency issues as I had to closely time align each recording, this needs closer inspection.
These results repeat what I obtained a week ago, more in the next few days.
Dan.
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That's pretty unfair to many of us who have to revise deeply seated opinions in the face of new evidence pretty often as our respective fields of research evolve. But as Bayesian analyses imply, it's going to require a very substantial amount of evidence to move the needle.
Now, ask John or Dan to revise their belief systems in the face of abundant fundamental evidence to the opposite. Do you realize how ridiculous this all is?!
If the cable is of sufficient length then you can do things like vary the characteristic impedance along the cable. Then it behaves differently in the two directions - but of course the cable is now asymmetric so this is unsurprising. The same trick does not work for short cables (e.g. domestic audio).Max Headroom said:
They are causes of resistance, which is a cause of thermal noise. I have seen nothing to suggest that they are sources of excess noise, which seems to be very small in metals. Given that thermal noise in an interconnect is negligible, anything smaller than this must be super-negligible.
It can make a significant difference to some mechanical properties, and an insignificant difference to electrical properties like resistance.
Only if the cable is long enough that transmission line behavioir becomes apparent, and only if these defects are asymmetric.indra1 said:
When you find some evidence we will be pleased to consider it, especially if a plausible explanation can be offered too.
Time align???
Just hearing that phrase tells me you have no control over your experiments.
You should be using a single mono source, you should be using the amp output difference as the metric. That is as sensitive as you are going to get.
Oh, and use dummy loads. If you are using speakers, the room reflections will impact the difference signal due to room reflection patterns, and you in the room alters that pattern as well.
Without the knowledge base, you are not going to be able to build an accurate test.
I'm glad to see you trying something, but you do not understand the confounders that ruin your tests.
Jn
I wonder why the expensive audio cable manufacturers have no real test results on directionality. I'm sure they are aware that real proof would help them sell more cables (and maybe even get them on the list for a Nobel prize ). The only reasons I can think of all point to there being no such phenomenon.
I mentioned similar issues to Dan in posts # 7670 and 7691.
Prerequisites, in my view are: one single plaback channel, one single record channel, loopback connection with the DUT cable, sample-sync'd recording, time alignment. With ASIO driver the TASCAM US-122/144-MkII is capable of all that with most any audio software.
The only thing that changes between runs is the RCA cable's direction (the interface has RCA outputs and TRS inputs, so with an RCA-to-TRS Adapter this is also really easy). Make 10 runs minimum, changing direction after each, so you have 5 sets of A and five sets of B and then compute the differences as described.
Alas, IME (and I do this kind of tests for quite some years now, sometimes even using that same soundcard), we will not find anything of significance in the residuals as they are still much too noisy. And clock and ref-voltage drifts also quickly start to dominate the residual once you try go deeper with heavy time domain averaging, can be mitigated by interleaving of the data to be subtracted and that needs some automatic synced switching of the cable direction. Further, the null must be fine-trimmed manually (because of the remaining drifts). Lastly, a much better soundcard than the TASCAM is very favorable. This is the level required to get down as deep into the details as needed for any directional differences which sure must be very small, very likely smaller than, say claimed copper vs. silver "character" (with same RLCD params, of course) . If they are readily apparent without effort (both in a simple diff test as well as by listening) I would suspect a "setup error" somewhere else.
Do you think that there is 1/f noise in analog switches like ADG819 when used in a
chopper? Are there frequency ranges that have been shown to be 1/f-free in this application?
Cheers,
Gerhard
Given that any decent network analyzer has elaborate 12-term error correction that
makes definitely sure that S21 == S12 and S11 == S22 across the port cables,
this would mean nothing but sloppy calibration.
regards,
Gerhard
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Thank you for being so patient with me. You reminded me to look more closely at RFI effects at the MHz range next time I come across a stupid cable. I once found fuzzy short repetitive mv level HF bursts (very difficult to see with my 20 MHz scope) at a linear PSU output a couple of years ago when I hunted down a noise problem. There are just too many factors.
Thank you for sharing of experience. I copied your posts to my HDD.
Thanks for clearing that up. I won't tell you how many times I have seen folks do that wrong...
@mmerrill99,
Thanks for bringing the New Yorker article to my attention; the book by Mercier/Sperber seems to be quite interesting.
@DPH,
I´m not sure why you see any unfairness in the cited statement as the key element was "if you set ...the prior belief at zero" .
If you _don´t_ do that, then new evidence will be able to convince you.
The statement and the key element are meant universal no matter which theory/hypothesis someone believes in......
Thanks for bringing the New Yorker article to my attention; the book by Mercier/Sperber seems to be quite interesting.
@DPH,
I´m not sure why you see any unfairness in the cited statement as the key element was "if you set ...the prior belief at zero" .
If you _don´t_ do that, then new evidence will be able to convince you.
The statement and the key element are meant universal no matter which theory/hypothesis someone believes in......
I have not seen any definitive studies. By frequency ranges do you mean low corner frequency? Taking this data is very time consuming and at some point you have to separate the process from the instrumentation.
I had the privilege of being taken to an associate's house about 1hr away (if traffic allows) to hear the latest upgrade of an amp that this engineer and I have been working on for about 10 years. At the same time, I got to hear what Jack Bybee is up to these days. I must say that my colleague's (the engineer) system had much more 'spaciousness' than what I am listening to at the moment. I realize that I have restricted myself to glorified MONO compared to what I heard at his house. Most of this is due to Jack Bybee's new inventions scattered around his listening area, and I got a couple to try myself. I can't tell you much about them however, too far out.
I am back from central america.... 115F and 90% humidity. And, I'm not walkiing in the shade. Glad i am outta there.
Cable directivity. What is the make model and brand and or type being used for audio T&M. I will get same and test myself.
I dont know of any directivity to just a plain coax. So, I will buy the cable with connectors in question being heard directionality.
Pls tell me.
THx-RNMarsh
Cable directivity. What is the make model and brand and or type being used for audio T&M. I will get same and test myself.
I dont know of any directivity to just a plain coax. So, I will buy the cable with connectors in question being heard directionality.
Pls tell me.
THx-RNMarsh
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Off the bat this is wrong in ignoring induced gate current noise of JFET and MOSFET amplifiers. I've posted the papers here or one could consult the literature.
Scott, I am only an arcing relay here. Nothing of true knowledge
https://www.edn.com/electronics-blogs/the-signal/4413341/Chopper-op-amps-and-noise
George
https://www.edn.com/electronics-blogs/the-signal/4413341/Chopper-op-amps-and-noise
George
Chasing faeries again.
The scientific, rational process is to FIRST show an effect (the plural of anecdote is not data) THEN look for mechanisms.
There's so much theory that you can go nuts dreaming up possible explanations. (Especially when you have no guidance from prodding the reproducible, captured effect.)
And it gets even worse when you have smart / experienced people doing it because you can dream up more and increasingly complex explanations.
...
Ya know, that's what's wrong with the Internet: like-minded smart people spinning endless explanations for things that haven't even been shown to exist or need explanations!
An intellectual circle-jerk of navel gazing!
Cheers,
Jeff
PS And get off my lawn!
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