[mojo]

Please just remember to turn the power off at the mains because electricity does not taste nice to cats.

 

[Grizzlepaw]

Zombie thread... Back from the dead!

We still don't have the full papers back from the U of T, but they did prepare a power point presentation for us as an overview of the testing results which I posted to the website.

Virtual Dynamics - Audiophile Audio Cable

it's been up there for a while.

 

[mojo]

Quote:

Originally Posted by Grizzlepaw /img/forum/go_quote.gif Zombie thread... Back from the dead! We still don't have the full papers back from the U of T, but they did prepare a power point presentation for us as an overview of the testing results which I posted to the website. Virtual Dynamics - Audiophile Audio Cable it's been up there for a while.

I don't see where it says that is from the "U of T" in the powerpoint slides, all it says is it was authored by "Ryan". Who at the U of T did the test?

Also, the conclusions drawn are a bit strange...

Slew rates on those scales for audio apps are meaningless. Typical line level output from a CD player or DAC is 3V peek to peek. That means that the "regular" cable could do a full peek-to-peek swing in 0.1us, or 1/10,000,000th of a second, or 10MHz. 10MHz is a bit beyond what most speakers can reproduce. So even if you played that square wave, the extreme possible example, the movement of the speaker cones would be the same with every cable. They just can't move that fast, in fact a tweeter that can go up to 44100Hz is 266 times slower.

The noise ratings for power cords are very odd as well. The numbers are well above what can normally be measured in a cable. The differences in the measurements (handily expanding by the scale of the graph) are too small to matter, or to put beyond manufacturing variance or error.

 

[Grizzlepaw]

Quote:

Originally Posted by mojo /img/forum/go_quote.gif Slew rates on those scales for audio apps are meaningless. Typical line level output from a CD player or DAC is 3V peek to peek. That means that the "regular" cable could do a full peek-to-peek swing in 0.1us, or 1/10,000,000th of a second, or 10MHz. 10MHz is a bit beyond what most speakers can reproduce. So even if you played that square wave, the extreme possible example, the movement of the speaker cones would be the same with every cable. They just can't move that fast, in fact a tweeter that can go up to 44100Hz is 266 times slower.

We manufacture digital cables as well as analog and for that application it definitely is important to have slew rate as high as possible, as to the rest, you can hear the difference in resolution. It's about reproducing the micro details of the wave, which requires a very high slew rate response. There any improvement is relevant, even at very short timescales.

If you want to argue audibility, go ahead. You won't get a very good argument going from me because I have heard the difference.

-Brad

 

[Febs]

Perhaps you could answer the actual question posed by mojo: Who at the U of T did the test?

 

[nick_charles]

Quote:

Originally Posted by Febs /img/forum/go_quote.gif Perhaps you could answer the actual question posed by mojo: Who at the U of T did the test?

My guess would be a group of undergraduate EE students, probably as a term project.

Without seeing the complete paper it is difficult to know what to make of it except...

1) In several slides they mix variables, i.e IC s and power cables in slides 8,9,10 and 11. What for instance was the analog cable when the power cable was changed. What was the power cable for each of the ICs ?

2) The generic IC is not identified by name or photographed, unless it is the grey one at the bottom of slide 6

3) Slide 4 contains an unsupported assertion Faster Response time means better sound quality, perhaps this is true but a citation is de minimus here.

4) The presentation has no references whatsoever.

5) Was the "original" slew rate calculated or measured. This is important since we are dealing with finite rise times.

6) The DVD.....ADC.......Laptop was single (1 channel )connections ?

7) Statistical analysis - there is none !, we do not know if these numbers are at all significant, at least a one-way Anova is required. Also the difference between the original wave and the best other slew rate is far ( 0.0105 vs 0.0052) greater that the difference between the worst and best other slew rate. Also the differences in noise levels looks very small was this tested for significance ?. Could this have been random variation ?

8 The difference between worst(stranded) and best(genesis) peak to peak slew rate on a nominal 2V signal (Slide 10) would be 1.46 microseconds viz
78.80 - 77.34 i.e 0.00000146s, I wonder if this is detectable by human ears ?

9) They did average 5 samples from each combination ?

10) No scale on the square wave diagrams, a 37hz square wave has a period of 0.027s or 27 milliseconds, you hardly need a microsecond (10 ^ -6) time scale for that

11) There is no rationale at all for the choices they made or their methodology, why use a 37hz square wave when you could use a higher frequency wave that would be far more challenging to a disc player? Why choose a DVD player and not a CD player ?

12) As mentioned earlier these noise figures are enormous, what do they mean ? A CD player has a noise floor of -96db (give or take) a -25db noise level added on by a cable looks bizarre and would swamp most low level signals.

13) Slide 10 - scale misleading, 0.0476 looks very close to 0.02586, the loss between original and "genesis" is 0.02176 , the difference between genesis and worst case is 0.00048 over 200x times worse

I would be happy to run some stats on the raw data if Virtual Dynamics would like to supply it.

I hope the final paper fills in the gaps, I look forward to reading it.

 

[bigshot]

Every time this company opens its mouth, it sticks its paw in it.

See ya
Steve

 

[Uncle Erik]

I'd like to know who performed this study. Was it sponsored by a department or was it just some students? Were the people who performed it compensated in any form?

 

[bigshot]

I think it's hibernation season again.

See ya
Steve

 

[Febs]

Quote:

Originally Posted by bigshot /img/forum/go_quote.gif I think it's hibernation season again. See ya Steve

Grizzlepaw has been online since nick_charles raised those points. He has apparently chosen not to respond.

 

[JohnFerrier]

Quote:

Originally Posted by Grizzlepaw /img/forum/go_quote.gif Interestingly enough I have the preliminary results of a DBT of our interconnects in my email inbox. We won't be presenting them until the middle of May (once the paper is finished) but it shows a definite correlation between the dynamic filtering and SOL (magnet) technologies and an increase in slew rate. I realize that just having my word on it isn't gonna be good anough for anyone, it wouldn't be good enough for me... Which is why we are putting in the money and time to have them tested by a third party (which doesn't mean we are paying to have them tested... the testing is being done for free, the money is the investment of materials, shipping, plane tickets to go down and film the results, ect.) So yeah, if that is really all it is gonna take Bigshot, then I expect a sales order from you to be crossing Rita's desk within 3 months or so... assuming that you aren't misrepresenting your position. There does remain the possibility, however, that you aren't actually interested in improving your sound and your components, but intellectually invested in stroking your ego on this board. I'm going to be generous and assume you actually meant what you said... Additionally, when you talk about our markups, do you want us to increase the price? Because if we were to bring our cables in line with other products in our industry we would have to double our current listed retail, at a minimum. Production cost is something we are trying quite hard to reduce, but getting the cables built in China just doesn't seem like a viable idea for us. The best way for us to bring production costs, and therefore the price to our end user, down at this point is for us to increase our volume, which means increasing market share. We're working on that. -Brad PS. The results will be out sometime after May 5th.

.

 

[nick_charles]

Quote:

Originally Posted by Febs /img/forum/go_quote.gif Perhaps you could answer the actual question posed by mojo: Who at the U of T did the test?

I woder if it could be related to a Walters Forensic Engineering Internship study carried out by a group of U.of T students ...

Supervisor: Jeff Archbold, M.A.Sc., P.Eng.
University of Toronto Engineering Students:
Visnu Siritharan
Diana Mollicone
Elnaz Ghasemi
Fatima Asad

who did this previous paper
https://www.virtualdynamics.ca/uploa...evised2007.pdf

A web search has revealed that one of the above 4 students returned to Walters Forensics for a second follow up study in Winter 2007 - 2008.

This paper (the one above) was editted, it is not the original paper and the original paper is no longer publicly available perhaps VD (or Walters Forensic Engineering) have a copy, perhaps they could post it here for us.

In any case I had a quick shufty at this paper and I can now see why they chose a 37hz square wave for the second study as the slew rate differences show up better, the differences in slew rates are greater though still small
0.0052V/microsecond vs 0.0013V/microsecond. The method is much the same. Thus one might posit that in the strongest music frequency ranges centering in the 300hz to 1000hz range the slew rate diferences would be in the order of 0.004 to 0.005V/microsecond.

I would like to know was this second study done under the aegis of Walters Forensics ? , if so did Walters Forensics volunteer to do another one pro bono or were they commissioned.

The original report states that Walters bought the power cable (unknown to VD) from VD. Presumably VD were then sent a copy of this report which they used in their advertising copy.

I do not know if it makes a difference but the boutique cable used in the first study was 12 gauge while the generic was 14 gauge, call me old fashioned but this looks like a confounding variable.

Finally the noise figures are vastly different from the noise figures in the later study ( ~ -41db vs ~ -25db) .

I have some reservations about the earlier paper, the use of different scales for a side by side comparison is highly misleading, not that they tell you what the scales are. They use the word significantly but show now statistical analyses to back this up.

 

[tourmaline]

Quote:

Originally Posted by mojo /img/forum/go_quote.gif I think we're being a bit hard on cats - without this playful feline we would never have discovered this rip-off! People regularly disassemble their amps and headphones, but rarely cables. At least not fully. Has this humble cat started a revolution?

Now, ain't that a cute cat. he knows alot about cables too!

 

[Budgie]

Looks to me like the differences attributed to the VD cables are so small as to be insignificant for audio listening.

These tests look more like an attempt to justify their claims, instead of proving a real difference.

 

[nick_charles]

Quote:

Originally Posted by Budgie /img/forum/go_quote.gif Looks to me like the differences attributed to the VD cables are so small as to be insignificant for audio listening.

This may be true or not. Certainly the differences are small in absolute terms ~ 1.5 microseconds peak to peak rise time, however jitter in the 10s of nanoseconds (10 ^ -9) range is audible. The bizarre thing is that blind listening tests would be pretty simple here.

You would just need one experimenter with a coin and a notebook to set up the cable and adjust levels, this experimenter would not be present during trials and would not communicate settings to the other experimenter who would coral subjects in and out and observe listening tests to take sure nobody peaked.

A stereo system including a preamp for level matching, a digital voltmeter, a large towel , a length of vacuum cleaner extension hose, a comfy chair and some subjects.