|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
68.104.246.173
In Reply to: RE: Why would I want selectable Digital Filters in a DAC? posted by jedrider on August 31, 2015 at 15:05:57
The sample rate of 44.1 kHz for CD playback is the main reason why we've had digital filtering, because there is such a small gap between the generally-accepted top of the audible range (20 kHz) and half the CD's sample rate (22.05 kHz), the highest reproducible frequency per Nyquist's Sampling Theorem. CD is ideally reproduced with full passband at 20 kHz with full stopband at 22.05 kHz. Since ringing would be introduced with "perfect" filtering with the passband and stopband so close together, time "smearing" exists at the top of the audible band.
So the sample rate of 44.1 kHz for CD playback leads to a compromise, top-end frequency response versus time response. The DAC's filtering can be optimized for either flat frequency response or time response. Or somewhere in between.
Long filters generally do best with flat measured frequency response to 20 kHz, but have "smeared" (ringing) time response. (These filters closest resemble the ideal filter per Shannon/Nyquist.) Short filters have a slightly rolled off top end at 20 kHz, and better time (transient) response than long filters. Non-oversampling filter-less designs (NOS) do best with transients and time response, but have the most "rolled off" top, due to nulls/modulation in the sampling toward the top of the audible band.
There is also a choice between "linear phase" and "minimum phase" filters. Linear phase has zero average phase error through the frequency range, but minimum phase filters better resolve the attacks and decays in music. (NOS designs do not have this option.)
If the music is heavy in HF information or transients, a short minimum phase filter might be ideal. If the music is more continuous, like Samuel Barber's "Adagio for Strings", a long linear phase filter might be ideal. If the music is small scale like a folk ballad or string quartet, a NOS design might be ideal. Your mileage may vary.
No single filter is ideal for all music. I generally prefer short minimum phase filters personally, if I were to choose just one filter type. But other listeners might prefer other filter types.
And finally, if you're loaned a DAC with these filter options, you can find out which filter types are most suited for your music and listening. You can then acquire a DAC with the filter type you most prefer.
Follow Ups:
I thought so.
I think when 44.1 kHz was selected for the sample rate (I still don't know how they decided on such an oddball frequency), there was too much faith in the Nyquist/Shannon Sampling Theorem, which unfortunately only holds true for steady state signals. But music isn't steady state. The theorem falls down with non-steady state "transient" events, where "ringing" is introduced in the time domain (using the so-called "perfect" sinc filter). So the "perfect" sound couldn't truly be perfect.I've had debates with theoretical engineers who thought I was a crackpot for questioning this theorem for audio application..... They treated the time domain issues as a strawman argument.
Edits: 09/02/15
it's forever.
Even live, maybe I don't like the type of strings that a player is using, etc. Then even this perfect "playback" is "flawed".
I eventually found that my goal is not perfect sound, but maximized enjoyment of music.
The "forever" part made those yuppies reach for their wallets. A good investment is nothing to sneeze at.
You need a nice (literally) clean CD, played on a Read Until Right transport with vanishingly low jitter, such as Parasound's CD-1, a S/PDIF cable that does not mess things up, and a superb DAC with sophisticated filters, such as Bricasti's M1.
Under such conditions, CDs can be astonishingly good, especially CDs that were themselves remasterings of golden-era master tapes.
Yes, an unedited raw pure DSD file will sound better--but in almost every case, there will be a better performance of that particular piece of music.
jm
SO few DACs and CD players truly bring the medium to its potential.
Prior to the experience I had with the Wadia 7/9 transport and DAC, I once thought CD was hopelessly inadequate for true high-fidelity playback..... Since that experience, my everlasting quest to replicate that Wadia experience.
It wasn't until I attained the Prism DA-2 DAC, and later the Don Allen/Philips CDC-935 CD changer, where I thought I could live with only CDs as my playback source. Yet even there, I still give vinyl a slight edge overall.
In regard to the time response/frequency response compromise with CD playback, I think the key is attaining a happy medium where neither flaw can be readily noticed. I once thought this couldn't be done, but I think I'm close.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
nt
Reebok can sound great. DSD and other formats can sound different, but better?
Setting aside the truly hi-res workflow, from recording to publishing (which still seems rare), are we really getting any more music or even verisimilitude from hi-res manipulation in the mastering chain if it's not captured at source?
Otherwise we may as well argue that we'll never, ever have perfect anything - or simply down tools as a species and camp right here, where we are now.
Big J
"... only a very few individuals understand as yet that personal salvation is a contradiction in terms."
I think redbook can be superb with good equipment. My vinyl sounds great and my cd's as well as streaming are wonderful. I enjoy my system no matter what medium I play back in and yes I have heard Hi-Rez downloads all the way up to DSD and don't find any more enjoyment from them.
Alan
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: