Home of the Squeezebox™ & Transporter® network music players.
Results 1 to 6 of 6
  1. #1
    Senior Member
    Join Date
    Sep 2006
    Location
    Danmark
    Posts
    1,361

    Digital volume control with 24bit recordings

    Hi,

    I know there's been a large number of threads on the volume control thing. *part* of the argument for, is that there is headroom for performing volume control in a 24bit system with 16bit recordings without loosing resolution, (not e.g. snr or dnr).

    But how are things with 24bit recordings? There is less to none headroom here? Which therefore makes direct to amp connections less flexible. So the recommendation in this case would be to use a pre, right?

    Part of the context of the question is that many are non-believers when it comes to higher than 4xkHz samplingrates, while the higher resolution seems much more accepted as giving improved SQ.

    Bj°rn

  2. #2
    Senior Member opaqueice's Avatar
    Join Date
    Feb 2006
    Location
    A place where something is or could be located; a site.
    Posts
    1,815
    Quote Originally Posted by bhaagensen View Post
    Hi,

    I know there's been a large number of threads on the volume control thing. *part* of the argument for, is that there is headroom for performing volume control in a 24bit system with 16bit recordings without loosing resolution, (not e.g. snr or dnr).
    The conclusion of those discussions was that the issue of "resolution" in digital volume controls is a misunderstanding and basically a myth. When you lower the volume digitally you lose in signal/noise, because the noise stays fixed (at least roughly) while the signal decreases. That's it. The errors introduced by digital volume rounding are in the least significant bit of 24 (since the SB3 etc. use 24 bit arithmetic), and therefore are 144 dB down and far below the level of noise already present in the recording and playback system, not to mention human perception.

    So I suppose if you start with a system and a recording for which the S/N is very large (at max volume), in some vague sense you have more to lose when you lower the volume. But since you started off better, what's the problem? The resulting S/N ratio will always be as good or better than it would have been in a 16 bit version of the same recording, for example.

  3. #3
    Senior Member Phil Leigh's Avatar
    Join Date
    Apr 2005
    Location
    Cornwall, England
    Posts
    9,991
    Precisely. "digital volume control" works pretty much perfectly on 24-bit.
    You want to see the signal path BEFORE it gets onto a CD/vinyl...it ain't what you'd call minimal...
    Touch(wired/W7)+Teddy Pardo PSU - Audiolense 3.3/2.0+INGUZ DRC - MF M1 DAC - Linn 5103 - full Aktiv 5.1 system (6x LK140's, ESPEK/TRIKAN/KATAN/SEIZMIK 10.5), Pekin Tuner, Townsend Supertweeters,VdH Toslink,Kimber 8TC Speaker & Chord Signature Plus Interconnect cables
    Stax4070+SRM7/II phones
    Kitchen Boom, Outdoors: SB Radio, Harmony One remote for everything.

  4. #4
    Senior Member Rodney_Gold's Avatar
    Join Date
    Dec 2007
    Location
    South Africa
    Posts
    188
    Bear in mind that you will never hear the full benefits of a 24 bit recording as thermal noise in components will decrease the resolution to about 21 bits anyway. If you have digital in the 24 bit domain , you will hear almost no ill effects by implementing digital attenuatiuon 1f that attenuation is done properly.
    SBT/Z-sys RDP1 digital Pre/Meridian DSP5500's Or TP/DSP5500's
    SBT/MDAC/Various amps/Osborn Epitomes
    SB3/Meridian DSP5000's
    SBT/ MDAC/Various HP amps/Senheisser Hd800's/650/600/Denon

    "The nicest thing about smacking your head against the wall is...the feeling you get when you stop"

  5. #5
    Senior Member Patrick Dixon's Avatar
    Join Date
    Apr 2005
    Location
    UK
    Posts
    1,805
    Quote Originally Posted by opaqueice View Post
    The conclusion of those discussions was that the issue of "resolution" in digital volume controls is a misunderstanding and basically a myth. When you lower the volume digitally you lose in signal/noise, because the noise stays fixed (at least roughly) while the signal decreases. That's it. The errors introduced by digital volume rounding are in the least significant bit of 24 (since the SB3 etc. use 24 bit arithmetic), and therefore are 144 dB down and far below the level of noise already present in the recording and playback system, not to mention human perception.
    Well those were your conclusions but not necessarily the conclusions.

    It should be clear even to you by now, that the lsb of a 24bit PCM signal is 144dB down on a full scale signal, but not on the actual recording (which should have some headroom even at its loudest points), or its (digitally) volume reduced version. It should also be clear that one type of 'noise' does not automatically mask another type of 'noise' at a lower level (if it did, you'd only hear the loudest instrument in any piece of music). The audibility of noise depends on the character of the noise as well as the absolute and relative levels.

  6. #6
    Senior Member opaqueice's Avatar
    Join Date
    Feb 2006
    Location
    A place where something is or could be located; a site.
    Posts
    1,815
    Quote Originally Posted by Patrick Dixon View Post
    Well those were your conclusions but not necessarily the conclusions.
    They were everyone's conclusions but yours, Patrick.

    It should be clear even to you by now, that the lsb of a 24bit PCM signal is 144dB down on a full scale signal, but not on the actual recording (which should have some headroom even at its loudest points), or its (digitally) volume reduced version. It should also be clear that one type of 'noise' does not automatically mask another type of 'noise' at a lower level (if it did, you'd only hear the loudest instrument in any piece of music). The audibility of noise depends on the character of the noise as well as the absolute and relative levels.
    144dB down from full scale is far, far, far below audibility on any conceivable home stereo system even with the volume at max. In fact at normal-high settings it is near or below the level of the noise produced by the Brownian motion of air molecules.

    This is obvious, because 0 dB SPL is by standard convention the threshold of human hearing. Hence, to make a -144dB signal audible, one would need full-scale to be 144dB SPL or more. 144dB SPL is much much louder than any stereo can produce - it is as loud as an automatic rifle being fired next to your ear, or a full-sized jet engine a few meters away.

    That is what is necessary to make a signal at -144 dB just barely audible when nothing else is playing. When music is playing it will be 130 dB or more above that, which at the requisite volume would blow out your hearing rapidly and permanently. And yet, you evidently believe that even if it were possible to achieve such absurd volume levels (which it isn't), that tiny -144dB whisper would be possible to hear through the excrutiating pain of your ear drums perforating?
    Last edited by opaqueice; 2008-09-24 at 13:30.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •