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Re: Unfinished Business: Cable Distortion Measurement Redux

Hi Steve, blindsiding again I see.

Blindsiding? What are you talking about? Are you only posting on diyAudio.com now? I know you said you like it better over there (I do too) but I seem to recall your still posting here on AA quite recently.

Would you rather I post this over on diyAudio.com?

You are misrepresenting the test.

I misrepresented nothing.

My test is essentially the same format as Cyril Bateman's test set-up in 'Electronics World' of capacitors for the last year. Cyril is NOT using any electronics better than is in my modified Soundtech 1700B analyzer. He gets results at levels similar to mine.

So? Perhaps it's because he's not using anything better than you that he's getting the results he's getting. That's why I've been wanting to try and have your tests repeated using something else. Preferably an Audio Precision rig.

What you leave out is my $25,000 self calibrating HP 3563 measurement system that actually analyzes the distortion 'null' data that follows the 1700B.

I didn't leave it out, John. Your HP 3563 wasn't used to make the plots in question which I posted in my message and which are the only plots of yours that I'm aware of which have been made public and the only evidence publically available to support your claims. And since you've said that you're effectiely getting the same results with the HP 3563 as you were with your Mac's sound card and Mac The Scope software, it's irrelevant.

For the record, I use the lowest noise, lowest distortion IC's available today in key spots in my 1700B analyzer, lowering its noise by about 15 dB from stock, and I don't know how much better distortion, but it is low enough to make wire comparisons.

Is it? How do you really know that? Are you saying that the actual circuit that an opamp is used in has no bearing whatsoever on the opamp's performance in that circuit? How do you know that using lower noise opamps aren't simply allowing you to see what your system is actually doing rather than what the device you're measuring is doing?

I have the greatest respect for Audio Precision, but they can't be using anything much better than I am now using internally, in their analyzer.

Again, are you saying that the actual circuit the opamps are being used in have no effect at all on the end performance of the system they're used in?

In any case, let's assume that AP's current topline system is only AS GOOD as your 1700B/Mac sound card/Mac The Scope software combination when it comes to distortion measurement.

That would mean that the System Two Cascade should have at least come up with the distortion levels that you're measuring under the same conditions. But according to Bruno, this wasn't the case.

So how do you explain this?

Simple logic would seem to dictate that there are just four possibilities here:

1. The Audio Precision System Two Cascade isn't even AS GOOD your 1700B/Mac sound card/Mac The Scope combo.

2. Bruno is lying.

3. By sheer coincidence, all of the cables Bruno used for his measurements just happened to be of such low distortion that not even your 1700B/Mac sound card/Mac The Scope combo would have been able to show any distortion products.

4. The distortion you're measuring is being produced by something other than the cables you're measuring.

As I have repeatedly stated, this test is easiest to perform with a 2 stage process, using 2 separate pieces of test equipment. Then the dynamic range of the test is much improved.

The System Two Cascade already does a 2 stage process. And why would using two completely separate pieces of equipment help improve the dynamic range? The additional external cabling, power supplies, grounding systems, etc. would only serve to introduce more noise as opposed to a single chassis system where noise performance can be better optimized.

I hope you (SE) will convey this info to Bruno, so that he gets a more balanced assessment of the test procedure.

I described what you used and what you did when you made the plots that I posted. You fed the post-null output of your 1700B into your Mac's sound card and produced the plots using Mac The Scope software with 100 averages.

And as far as I'm aware, you have not stated that these plots are not representative of what you have been measuring since then.

se





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