|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
47.221.171.71
In Reply to: RE: RIP Peter Aczel posted by Bob Rex on June 25, 2017 at 06:52:31
The article is titled The 91st Audio Engineering Society Convention; or, The Invasion of the Credibility Snatchers, and it's from issue 17 of The Audio Critic (PDF).
Follow Ups:
I didn't have a copy of that issue and I'm trying to acquire all I can. Excellent, biting comedy. Thanks!
...who clearly heard the differences he described between nearly 20 preamps he reviewed in his first issue.
What changed - his hearing acuity or his attitude toward audiophiles and the audio industry?
It wasn't my intent to revive the cable debate. As I mentioned in my reply to John, I liked the article because of its colorful description of the culture clash that occurred: the clapping, whistling and stomping of feet etc.
...written by a charlatan.
> The article is titled The 91st Audio Engineering Society Convention; or,
> The Invasion of the Credibility Snatchers, and it's from issue 17 of The
> Audio Critic (PDF).For another report on what we called "Audio McCarthyism," see the article
linked below, which includes a large number of letters in response that we
published.
John Atkinson
Editor, Stereophile
Edits: 07/04/17
John Atkinson wrote:
"For another report on what we called "AuioMcCartyim," see the article linked below, which includes a large number of letters in response that we published. "
I didn't consider the mention of cables in the article to be its central theme, nor is it the reason I like the article so much. What I like is its colorful depiction of the clash of cultures that played out at the convention. It is a kind of unintentional allegory, representing a broader conflict within the audio industry.
"The amplifier thus saw both cables' capacitance at all times."
As you find with the equally amusing non-test found here . Scroll down for the Interconnect section about the Y-adapter test.
I even tested the test apparatus with my trusty capacitance meter. Yes, Virginia you are comparing the capacitance of A+B+Y adapter at either end. One bright soul here told me effectively "well if you assume the devices have zero impedance, then that is correct. " Yes, if you begin your circular reasoning with there's no difference, then the test confirms it! :)
Same misunderstanding. You still can't grasp the concept and appear to have a complete block on this one. :)
Maybe a different example might tweak your understanding. Consider a standard crossover in a two-way speaker system. Both filter sections are "Y"ed to the same source, yet the woofer and tweeter receive completely different signals. How is that possible? :)
Dave.
Well, if you want to get pedantic about it, they do see the same signal. Up to the point where the reactive components start attenuating the signal differently. And by the way, the woofer's inductive behavior, does interact with the tweeter's capacitive behavior. The only way to truly isolate the contributions of each is eliminate the crossover from the driving part of the circuit and bi-amp.
Now regarding the Y splitter and 2 differing cables. The impedance characteristics of both cables will combine, and the complex impedance will be a function of both cables, as well as the splitter.
I've measured it. For some reason Mr. Circular Reasoning believes two far-fetched concepts:1. The DAC, preamp, amplifier somehow "know" that the capacitive load is composed of multiple components and will *exempt* the contribution on the far side of a Y-adapter. Right.
2. For a "valid comparision", one needs a perfect voltage source. Well, if you live in a theoretical world, maybe that works. As for me, I live in the real world of real devices that don't have the knowledge nor care how the load is built and react to the load presented via - one cable, multiple cables attached via adapters, multiple cables with parasitic ones attached via Y-adapters, one with a capacitor attached across leads, etc.
Raise your hand if any , much less all of the components in your system exhibit zero output impedance. Certainly not mine. Not the phono cartridge. Not the DAC. Not the preamp.
I find his theoretical ramblings quite humorous indeed.
Edits: 07/07/17 07/07/17
I raise my hand. I have a couple of different headphone amplifiers that have less than 0.25 ohm output impedance. Real world (not theoretical) devices that are appropriate for said interconnect A/B comparison.
Regards, the speaker-level example.....I hope you're not suggesting that a woofer and tweeter receive the same signal. If that's the case you'd have a crossover that doesn't cross over. Fantastic! Contact the AES!
Dave.
I raise my hand. I have a couple of different headphone amplifiers that have less than 0.25 ohm output impedance. <
I hereby award you a gold star!
Regards, the speaker-level example.....
The context of my comments about Roger's laughable and measureably false interconnect *test* has always been about that subject and I certainly don't use them to drive speakers. You're welcome to start a new thread about your focus of interest.
I revisited your text book example of circular reasoning and still shake my head and smile. :)
The capacitance is not significant IF the driving source is not affected by it.
If a frog had wings, he wouldn't bump his ass!
You should have continued to read in that thread. Long after you ran out of gas/understanding I elaborated on the situation more fully with Satie.
I never said the published Sanders scheme was without some possible pitfalls/variables. (I highlighted them in fact.)
But, if those variables are removed the concept is sound and you will have a valid A/B comparison between two interconnect cables.
The speaker-level example is a more real-world scheme that I thought (incorrectly) you could grasp. Take a simple, two-way speaker crossover and attach two identical full-range drivers to both outputs. The resultant output from the two drivers will be different. That should be obvious since you have a low-pass and high-pass filter driving them.
The two interconnect example is the same thing. You again have a common source coupled via two LCR filters (in this case they're both low-pass filters) to identical loads. If the LCR characteristics of those two interconnects are different enough you will hear (and measure) a difference. The reason you won't expect to hear much (if any) difference between two interconnect cables is not because the scheme is flawed...it's because there simply isn't that much difference the interconnect cables could contribute.
Hopefully you've read this far..... This is very straightforward real-world methodology. There's nothing circular about it.
I realize the ship has sailed, but more attempts at real understanding and less silly knee-jerking audiophilia would do you well.
Dave.
observing more ways you demonstrate a lack of awareness. :)You should have continued to read in that thread.
I did. Let's review the continuation, shall we?
Mr. Circular Reasoning: "The voltage source will supply exactly the same current to cable A regardless of whether the Y-connector and cable B is attached or not."
Another voice of logic (Satie): "That is not correct, which is what I am saying and which is what I don't understand why you don't see it. "
The speaker-level example is a more real-world scheme
The topic remains around interconnects. Why is that so difficult for you to understand? I'll repeat what I said in the previous post: if you want to talk about speaker level issue, then create a new post. Comprende? Do you understand Engrish?
If the LCR characteristics of those two interconnects are different enough you will hear (and measure) a difference.
No $hit Sherlock! I've asked the question before and I'll ask it again even if you remain incapable of responding another time!
"Do you believe 74, 510 and 626 represent the same value? "
Maybe I need to ask the question again if you missed it.
"Do you believe 74, 510 and 626 represent the same value? "
Do try to wrap your head around this simple notion this time. Is it beyond your scope of awareness? Sheesh!
The reason you won't expect to hear much (if any) difference between two interconnect cables is not because the scheme is flawed..
That is just too funny! The idea behind a cable comparison is to.. well compare different cables (presumably by themselves)! When one forces each to share the combined characteristics of both, there is no longer a comparison - other than A+B vs A+B. What does any (intelligent) person expect? Apparently, present company excepted!
it's because there simply isn't that much difference the interconnect cables could contribute.
Opinion so noted. And contrary to my experience.
I realize the ship has sailed
I wish you the best of luck convincing anyone of your bizarre lack of understanding. :)
Me: Fail
Satie: Fail
Bob R: Fail
Edits: 07/08/17
If not interested in learning, then obviously you're wasting your time. :)
You still can't get past the A+B vs A+B premise/comparison? My goodness.
The voltage source removes the "+" from that comparison. So, you do actually have an A OR B comparison even though connected to a common source. I'm not sure how much simpler I can explain it to your feeble brain. The voltage source becomes the buffer between the two (A or B) interconnect evaluations.
This really is BASIC electronic stuff. :) I've been working in the electronic instrumentation world for many years and this is bread and butter.
Dave.
I confess that I'm not surprised you remain incapable of answering simple questions. Multiple times.
This really is BASIC electronic stuff.
Second logic fallacy: appeal to authority
Obviously, with zero content to support it - because there is none.
I've been working in the electronic instrumentation world for many years and this is bread and butter.
Hopefully I never purchase any electronic device where the designer doesn't understand the difference between 74 and 626.
"I've just wired your new home! Don't mind that you'll find 74 volts at some outlets and 626 at others. It's because there simply isn't that much difference" :)
We're loving the humor!
Hang in there. One of these years this subject will illuminate for you and you'll think back and say......"Aha, that's what he was talking about."
Dave.
non-responses to simple questions. Sorry to go over your head with them. Clearly, no one is surprised with your lack of any content to support the farce.Aha, that's what he was talking about."
You're not only clueless but don't pay any attention to my previous comments. Interconnects have already made a substantial audible difference in my system. Is anyone home?
So, what hallucinatory drugs do you take to derive your point of view?
edit: I'm aware you make DSP crossovers for Siggy's speakers. That's enough for me to never consider them for purchase.
Edits: 07/08/17
They do see the same signal? Are you sure about that?? :)
I think you'll find that only at one single frequency do the woofer and tweeter receive exactly the same signal.Yet another person who doesn't understand the concept. My goodness.
I suggest to read up on voltage sources.
Also read up on the specific requirements for this test called out by the engineers who have advocated it. You do need to satisfy some requirements for it to be valid.The primary requirement is: for this "separation" of networks to occur and a valid A/B comparison to result, you do need to have a real-world source that is pretty close to a theoretical voltage source. For interconnect testing something like a zero ohm headphone amplifier would work well. For power amplifier testing, a solid-state amp with very low output impedance. If you satisfy that requirement in the conventional two-way speaker system example I mentioned, you'll find that disconnecting either the woofer/network or the tweeter/network individually will not alter the operation of the other in a significant way. When both are connected, the two legs will have minimal/no interaction with each other.
In either case, the characteristics will lump.....but only as seen by the source....which should be a voltage source. In that case, regards the loads, the networks will operate as if the other were not connected.
This is basic stuff fellas.
Dave.
Edits: 07/06/17 07/06/17 07/06/17 07/06/17 07/07/17 07/07/17
They do see the same signal? Are you sure about that?? :)
I think you'll find that only at one single frequency do the woofer and tweeter receive exactly the same signal.
Yet another person who doesn't understand the concept. My goodness.
They never receive the same signal at any frequency. At the frequency where the amplitudes are equal, the phase is different.
And I don't know why you insist on pushing the crossover analogy in this thread. It really is irrelevant. Your point seems to be that two interconnects hanging off a switch box makes two parallel LCR networks, and hey, a crossover has two parallel LCR networks too! Therefore they must be comparable. Well, no they are not. The crossover is designed to be a frequency dividing network with cutoffs in the middle of the audio band. The interconnects are not. Neither is the switch box. And the source impedances are vastly different, and the loads are vastly different too. There is literally nothing comparable in your analogy.
I suggest to read up on voltage sources.
Also read up on the specific requirements for this test called out by the engineers who have advocated it. You do need to satisfy some requirements for it to be valid.
The primary requirement is: for this "separation" of networks to occur and a valid A/B comparison to result, you do need to have a real-world source that is pretty close to a theoretical voltage source. For interconnect testing something like a zero ohm headphone amplifier would work well. For power amplifier testing, a solid-state amp with very low output impedance. If you satisfy that requirement in the conventional two-way speaker system example I mentioned, you'll find that disconnecting either the woofer/network or the tweeter/network individually will not alter the operation of the other in a significant way. When both are connected, the two legs will have minimal/no interaction with each other.
In either case, the characteristics will lump.....but only as seen by the source....which should be a voltage source. In that case, regards the loads, the networks will operate as if the other were not connected.
This is basic stuff fellas.
That's totally irrelevant because the output stage of a source component or pre-amp is far, far from an ideal voltage source. Typical output impedance values for components with solid state output stages vary from a few 10s of ohms to a few hundred ohms. For tube gear it's typically a few hundred up to a few thousand. And these impedances are reactive too, with output transformers and/or caps around the output for isolation, DC blocking, and filtering.
Let's go back to basics. An ABX test is a statistical hypothesis test. The hypothesis is that two different line level interconnects produce audibly different results during music playback from an audio system. A valid ABX test of the hypothesis can only be performed if the design of the experiment preserves or duplicates the conditions under which the hypothesis could be true. If your experiment depends on using a source that behaves as an ideal voltage source and isn't representative of a typical audio source component or pre-amp, then you aren't testing the hypothesis.
Using a typical audio pre-amp driving a typical audio power amp, you can't hand wave away the fact that this particular test setup makes the parallel capacitance of A the same as the parallel capacitance of B which equals the sum of the two interconnects. The open-circuited interconnect hanging off the switchbox may also be conducting RFI into the circuit under test. Even the switchbox itself is a problem. The mere presence of the switchbox in the circuit could invalidate the test unless its impedance is a couple orders of magnitude less than the cables under test. And you would have to be sure that the switchbox doesn't introduce a path for RFI or EMI to enter the circuit, and the switchbox has to preserve the relationship between the grounds of the source and sink components.
The QSC and AVA ABX comparators, for example, are essentially passive pre-amps. When you put one of those things in the circuit, you are not testing the original hypothesis.
Dave,You've highlighted some valid qualifiers of the Sanders test in question. (I noted those as well three years ago when this was mentioned by "E-Stat" on the other forum.)
Yes indeed there are some issues with the A/B testing as Sanders as outlined it, but what I was trying to do then (as now) is give Roger the benefit of the doubt regarding his thinking on the basic validity of the concept. I'm not the originator of this, but I do understand what Roger is getting at.
I was then elaborating on his scheme with things that would make it much more valid. But by this time, the heels were well dug in by other posters. :)The speaker crossover analogy was not the best, but I was trying to highlight a similar scheme that might be more understandable for E-Stat. He had suggested awhile back that for any common source split path network configuration all the characteristics would lump and yield identical signals at both destinations. (This is the basic premise of his whole rejection of the Sanders scheme.)
In the speaker analogy, yes indeed, even at the one frequency where the low-pass and high-pass filters are exactly the same amplitude there 'may' be a phase difference. But the "they do see the same signal" statement posited by Bob Rex is clearly incorrect.
I will stipulate this whole concept is tricky for some to get their heads wrapped around. Circuit analysis here and how some parameters lump is more complicated than it might seem.
The rest of your post regarding ABX testing clouds the issue, a bit. Typical audio sources not being theoretical voltage sources...non-used open-circuited interconnects...switchbox concerns, etc, etc, are all qualifiers that may invalidate the scheme. All of these (and others) I already noted three years ago.
Let me reiterate again....I have NEVER said there aren't some possible issues with the Sanders interconnect testing scheme. :) But unlike others, I don't completely reject it out of hand because of a few issues.If you haven't already, check out the original paper from Roger Sanders and you decide how misguided his thinking is on this topic.
http://sanderssoundsystems.com/technical-white-papers/54-cables-white-paperCheers,
Dave.
Edits: 07/10/17 07/10/17 07/10/17
Thank you for the reasonable response.
My point of view on this topic is that when it comes to ABX'ing audio cables, the only way to make sure you're not introducing other variables into the audio system is to swap the cables, which is tedious and makes it impossible for the listener to utilize short term auditory memory to make the comparison. I can't think of any easy way to allow quick switching without introducing something into the circuit whose effect on the circuit performance is on the order of the cables themselves, if not greater.
Some time ago, I recall reading the comments of Frank van Alstine who insisted his second generation ABX comparator was completely transparent and suitable for cable comparisons because it had no active components or capacitors in the signal path, just a network of relays for switching and attenuators for volume control (he had gotten rid of the cap coupling in the second gen). The box contained a power supply, and digital control and display circuitry, and his single ended circuitry introduced a whole new ground path. It was essentially a digitally controlled passive pre-amp.
The underlying basis of the hypothesis is that differences in the relatively small impedances of audio cables and connectors, possibly combined with differences in shielding, or other construction details, is enough to make them audibly different to certain individuals in certain systems. Regardless of whether or not you believe this hypothesis to be true or false, in order to test it you have to preserve the details under which the hypothesis could be true. That is something that Frank and many other ABX proponents seem to have a mental block about.
In the case of Sanders, it could be that he just didn't think through the details of his proposal. Or it could be that he assumed a-priori that the cable capacitance couldn't matter, and therefore he didn't have to control for it.
Dave.
Good points. Obviously you are correct that to 100%, absolutely, fully, maximize, etc, etc, control an A/B test like this, you would not parallel the interconnects onto a single source....without some facility to completely switch out the unused one.
I have talked with Roger a few times, but not regarding this interconnect cable test scheme. So, I'm not really sure what his specific thinking was/is.
Regards lumping of characteristics: If we really want to get down into the weeds on this, the capacitances of two, simultaneously connected interconnect cables do not strictly appear in parallel with each other. Even a simplified equivalent circuit would illustrate this. There are multiple series and shunting elements to consider.
Regards possible ABX testing and gadgets to achieve it, it really is a can of worms with numerous potential pitfalls. I'm well aware. :)
Dave.
> I have NEVER said there aren't some possible issues with the Sanders interconnect testing scheme. :) But unlike others, I don't completely reject it out of hand because of a few issues.>
Not possible issues - ISSUES.
You don't reject it, even though it is flawed, because it fits your biases.
So if you don't control ALL of the variables in a scientific test, how is it a valid scientific test?
Do you understand the scientific method?
Your test is pseudoscience - a parlor trick to make audible differences disappear.
So it's MY test now?? :)
I'm not the one that came up with this scheme.....let's not lose sight of that.AND you've identified by biases too. Excellent! :)
Dave.
Edits: 07/10/17
The context is interconnects and if you would like to assume that an 80 pF one is identical in performance to one measuring 600 pF, that continues to be fine with me. :)
Sorry, but my experience has demonstrtated otherwise with the components they connect.
Some things are true whether we believe them or not.
Yes, the context of my example is different, but the concept is identical. Maybe the fact that you can't see that is the issue.
Forget me for a second...your position puts you at odds with some knowledgeable engineers. And you appear to have zero intellectual curiosity to try and understand your misunderstanding. That's unfortunate.
Oh well.
Dave.
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: