[ProAudio] The High-Resolution Challenge

[Bill Whitlock]

I strongly agree that ultra-sonic spectral artifacts, even if low level, can have clearly audible effects. The late Deane Jensen wrote a paper called "Spectral Contamination" that explains the mechanism and describes a test. As was mentioned earlier in this thread, complex inter-modulation occurs in virtually every active stage downstream of the DAC.
What makes the "distortions" so irritating to the ear is that many, if not most, of the inter-modulation products are non-harmonically related to anything in the input spectrum - it's often described as "grunge" or a "veil."  The cure is to limit bandwidth, preferably with passive filters, between every active stage in the signal chain. Of course, the filters must be designed to have linear phase (constant delay) vs frequency to avoid time-domain distortion. In fact, near-perfect time-domain response to 20 kHz can be had in a 25 kHz bandwidth if the overall filter has a Bessel response characteristic. To this end, Deane designed all Jensen transformers to have a high-frequency roll-off that followed a 2nd-order Bessel response (this also makes their square-wave response near-perfect).  The only other way to get linear phase response is very wide bandwidth - and this "easy" way comes with the penalty of passing ultra-sonic spectral components and worsening spectral contamination.  Oh yes, Deane wrote another important paper debunking the idea that phase shift means phase distortion (hint: phase shift that varies linearly with frequency is nothing but a time delay). And he coined the term for true phase distortion, DLP or deviation from linear phase. It's why you'll see a DLP spec on every Jensen data sheet. Very often, Jensen audiophile customers would by an ISO-MAX (transformer in a box) to eliminate a hum in their system - then call back to report that not only was the hum gone, but their system now had this amazing new clarity!  It was due to the phase-accurate bandwidth limiting (to about 50 kHz) of the transformer, which reduced spectral contamination distortion in downstream gear (power amplifiers are usually the worst contributors).
IMHO, the time-domain response of the anti-alias filters in early digital recorders is what gave digital recording a "black eye" right from the start. Deane did an AES local chapter meeting presentation back in the day. He showed waveforms of a cymbal crash in and out of an early Sony recorder. Not only was the waveform unrecognizable, the cymbal sounded like it was made of lead!  Fortunately, modern "over-sampling" A/D converters don't need such "brick-wall" anti-alias filters - and have largely overcome this problem.
Sorry about the rant - excessive bandwidth is a pet peeve of mine! I'll try to provide a link (possibly at the Jensen website) for these papers.
Bill WhitlockWhitlock ConsultingVentura, CAAES Life FellowIEEE Life Senior


-----Original Message-----
From: Dan Lavry via ProAudio <proaudio at bach.pgm.com>
To: mastering <mastering at telia.com>; proaudio <proaudio at bach.pgm.com>
Sent: Thu, Feb 13, 2020 4:49 pm
Subject: Re: [ProAudio] The High-Resolution Challenge

 The paper you send is stating clearly that they don't know the reason to the conclusing they made.Using specific gear means having many variables that can change the outcome. It is not good enough to form generalizations. My friend from Sony and his team did a extensive comparisons between 96 and 192KHz, they did it for internal use, but he told me that 96khz was the prfered one.I don't have to take sides. But let me point out that my statements were correct, free of any variables. I speak EE and math, and non linearity is generally bad. I already said a lot about the subject (years ago) in my paper Sampling Theory. I added the issue of non linearity when someone here sugested here that the energy above audio frequencies does not matter. How much it matters? Again, I leave that to the recording and mastering people. (Personaly, I don't think it should be dismissed).
RegardsDan Lavry


Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------
From: "Goran Finnberg mastering at telia.com" <mastering at telia.com> 
Date: 2/13/20 2:17 PM (GMT-08:00) 
To: Dan Lavry <dan at lavryengineering.com>, proaudio at bach.pgm.com 
Subject: The High-Resolution Challenge 

Dan Lavry:
>So why 192 kHz or higher? If you can't hear it, and your dog can't either...

https://web.archive.org/web/20030407091305if_/http://www.dcsltd.co.uk:80/papers/effects.pdf

---------
Best regards,

Goran Finnberg
The Mastering Room AB
Goteborg
Sweden

E-mail: mastering at telia.com

Learn from the mistakes of others, you can never live long enough to
make them all yourself.    -   John Luther

(\__/)
(='.'=)
(")_(") Aron, VovVov, Nero & Smurfen:RIP
_______________________________________________
ProAudio mailing list
ProAudio at bach.pgm.com
http://bach.pgm.com/mailman/listinfo/proaudio
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://bach.pgm.com/pipermail/proaudio/attachments/20200214/d489b9dc/attachment-0001.html>