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In Reply to: RE: Raspberry Pi 3 as USB audio streamer - some audiophile settings to try... posted by Archimago on January 07, 2017 at 11:41:11
I've always speculated that systems with the biggest emi problems benefit the most from these tweaks aimed at reducing emi. Those systems with very small emi problems will achieve relatively fewer appreciable benefits I'd guess.
You have apparently been able to achieve fairly heroicly low levels of emi in your various loopback configurations considering at least part of the analog chain is single ended circuitry, ie the forte aaand you are apparently hooked to a pc somehow via usb in order to run RMAA...
Your capture systems decent apparent emi performance may be why you couldn't measure or hear much of a difference from these kinds of tweaks if that is indeed the case.
In other words, I'm wondering if your system may be too high performance at rejecting emi to really show why these tweaks may be so valuable in some systems.
You could possibly test my theory by trying to replicate the emi vulnerability extremes and rerun so called emi tweak tests.
1. You'd need an "ideal" test system. Perhaps your existing system is already good enough for this. Ensure optimal emi hardening via proper grounding, etc. I'd suggest you could possibly be able to achieve even better emi results than you are getting now with a fully balanced analog signal path in your loopback.
2. create a "worst" case system to test. Easy. Get some single ended gear and throw in some massive ground loops.
Follow Ups:
His DAC filters most of the stuff above the audio band.
His ADC filters most of the stuff above the audio band.
His conclusion only means, that no matter
what source he's using his DAC/ADC combo measures
the same way (on his questionable tools) in the audio band.
This has nothing to do with the noise originated from different
sources. Nor it can lead to any conclusions related to the source.
His measurement methods are pretty much ridiculous.
And he keeps spreading his crap (doing it for years).
As a starter - I recommend to read this:
http://nwavguy.blogspot.de/2011/02/rightmark-audio-analyzer-rmaa.html
Enjoy.
His Dac and ADC presumably respond in the audio band. We as audio enthusiasts presumably care most about what is within the audible ranges.
If the theory us that these system changes are responsible for making changes in the audible noise profile then presumably having more ability to resolve noise within the audible band will help the test results be more useful regardless of whether or not his results are calibrated to some standard.
To say that the RMAA SNR testing results in this case has absolutely nothing to do with noise would seem a bit short sighted by my estimate.
The high res RMAA plots show evidence of what is almost certainly unintended emi creeping into the audible signal being sampled. Getting rid of it could make it easier to identify low level changes in noise profile which are within this systems ability to respond to it. Having the other noise sources gone from the picture could make it easier to identify low level changes if thy happen to cause system response that is made visible by the test.
Though the results certainly mean the most within the context of this test setup and can't easily be directly correlated to other systems, the relative differences could certainly be meaningful if they actually showed appreciable difference.
Meaningful in that if changes are detected by the test, other users could more reasonably wonder if similar changes might have some effect on their own systems.
Look.
Since years Archimago tries to explain "Computer Audio" with his
way of measurements.
He is pretty immune against any feedback/criticism.
And he seriously believes that he can prove everything, where
professionals with measurement equipment worth ten thousands of $ fail.
His measurements are OK for basic checkups. And that's about it.
"And he seriously believes that he can prove everything,"
It would be a shame to try and read too much into any results, maybe I missed where the OP did that in this case.
"where professionals with measurement equipment worth ten thousands of $ fail."
If these tests are already being performed by more qualified individuals on more accurate gear and the results are being submitted somewhere into the public domain for public discussion similar to how the OP is doing these articles I would sure love to learn where this is going on so I could see it for myself.
My impression has been the guys with the good test equipment are either working for manufacturers and therefore paid to paint their gear in the best light and so therefore a questionable source of reliable comparisons OR work for the media and always too afraid of biting the hand that feeds them to truly pit one manufacturers gear against anothers in truly scientific shootout form.
Those who are not, have only themselves to blame.
His measurements are suitable, to determine whether a piece of equipment is broken, or grossly misrepresented by manufacturer - that's it. NOTHING beyond that.
Do I personally think his work is in any way useful? No, I do not - but hey, it's as good of a hobby as anything else out there.
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