Ayre CX7e vs. Meridain G08

Bigtee -

I have noticed the same phenomenon you have -- increasing levels of jitter over the years in the Stereophile test reports. JA made an oblique reference to this in one or two of the testing sidebars -- something to the effect that you can't compare the numbers in the newer test reports with those of the older test reports. Unfortunately, he did not say why.

I tried to duplicate his test results for the Ayre C-5xe with a slightly different setup. The test disc is easily made, using specifications from an AES paper (by the late Michael Gerzon, I believe). I analyzed the output with the FFT function of both an Audio Precision System One (and older machine like Stereophile uses for most of their measurements), as well as the latest, greatest Audio Precision 2722.

With the System One, there were a lot of spurious sidebars as well as a generally higher noise floor than JA reported with his Miller Audio Research analyzer. But with the 2722, the noise floor was markedly lower than JA's tests. Further there were *no* sidebars at all when using 24-bit data, implying that all of the sidebars I found with that machine in 16-bit mode were data related and therefore an artifact of the test itself.

My conclusion is that this test protocol is extremely sensitive to the test equipment being used. I further speculate that something has degraded in JA's test setup over the years, leading to falsely high readings in more recent tests.

This is unfortunate, as many readers rely on these test reports. I hope that JA addresses this issue soon, and preferably in print.

Charles Hansen
Ayre Acoustics, Inc.

Mr. Hansen: I recall JA once writing something to the effect of cautioning that his jitter test results should only be compared to his own past numbers -- that they can't be cross-compared with numbers from other sources, and that it's where they fall within the spectrum of his past results that matters, rather than the absolute numbers themselves. Given that proviso, and the fact that he frequently characterizes how his figures for a unit under test compare to his historical upper echelon, one would think he couldn't fail to notice and take corrective action if needed (or note the poorer performance of recent players) should his results show a clear trend of worsening over time. Since he hasn't written anything like that, my assumption would be that if you contacted him about this question he'd probably say that, notwithstanding any one-time unspecified changes to his test set-up or method such as you noted, there is no such overall trend. Don't know if that would be correct or not, but personally I'm not about to go through my back issues of Stereophile and track his figures to try and find out...

Mr. Hansen, First let me say I hope you're recovering well from your accident and will be back over at Ayre soon.
Second, thanks for contributing to this forum. It's always relevant to have a designer with your reputation contribute.
I think you are absolutely correct in your statements. I have felt there might be a reason along these lines but I also felt JA would stay on top of his test equipment.
It was a surprise to see jitter at the level JA found with the C5xe knowing how good it sounds and what results from jitter. I also know your attention to detail in your products. Both the CX7e and C5xe are superb products in their respective price ranges.
Since JA does all of Stereophile testing, it casts doubt in my mind how much merit to give to some of these measurements at this time. It seems something is a little off.
I know test measurements aren't everything but I do believe certain parameters on a test bench do correlate to the sonic end result.
Keep up the good work over at Ayre.

Hello Zaikesman,

Sorry you choose not to believe me. Here is proof of what I am talking about:

Go to the bottom of Stereophile's review of the dCS Verona master clock:

http://stereophile.com/digitalprocessors/305dcs/index4.html

and you will see the following footnote:

"Footnote 1: For reasons unknown, all these measured jitter levels are about twice what I measured for the Elgar and Verdi two years ago. They should therefore be considered as relative rather than absolute values."

Now I don't know about you, but I consider a 100% variation in test results over a two-year span to be problematic at best. I did contact him about this several months ago, but with no substantive reply to date. I suspect that he is pretty busy and that this is not high on his priority list.

Charles Hansen
Ayre Acoustics, Inc.

I went back and read the CX7(not the CX7e) review from the May 2003 Stereophile. JA stated the CX7 had some of the lowest jitter(159 picoseconds of peak to peak) of any player he had measured.
The higher levels of jitter seemed to start showing up about 2 years ago or less. It would be interesting to re-measure that same player now.