atkinsonrr;141569 Wrote: > But maybe if someone could run us through the technical rationale for > why attenuation in 24 bits will not affect sound? Anyone? Digital volume control is fine, provided your basic gain settings are correct. Let's take two examples, one based on the ideal gain setting situation, and the other a catastrophically bad one:
1. Say the maximum level you ever want to listen at is 120dBA. You somehow manage to set up your power amp/speaker combination so that you get 120dBA when the Squeezebox/Transporter is at maximum volume. Now, with 24 bits of resolution, the theoretical quantisation noise is 144dB below the listening level, ie. at -24dBA. Since 0dbA is the threshold of audibility, this noise is indiputably inaudible. Now use digital volume control to turn the level. Let's be brutal and throw away a whole 10 bits of resolution - bringing us down to just 14 bits. At this setting, the level you're listening at is 60dBA (fairly quiet). With only 14 bits of resolution, the quantisation noise is 84dB down. And that's *still* at -24dBA, ie. still inaudble. Basically, provided your basic gain settings are at a level where the quantisation noise is below the threshold of audibility, it remains so regardless of the digital attenuation. 2. Now consider the opposite extreme. You have a massively powerful amp and hugely efficient speakers, so that to listen at 120dBA, you need to use 60dB of digital attenuation. Now your quantisation noise is 84dB beneath 120dBA, ie. at 36dBA. This could be audible. Therefore, whether or not digital volume control can lead to audible loss of resolution is entirely down to the gain setting of the rest of the system. Most practical systems fall between the two extremes discussed above, of course. If a system has too much gain, it's easy to use passive attenuation to correct the situation. If you have too little gain, you'll need additional active amplification. -- cliveb Performers -> dozens of mixers and effects -> clipped/hypercompressed mastering -> you think a few extra ps of jitter matters? ------------------------------------------------------------------------ cliveb's Profile: http://forums.slimdevices.com/member.php?userid=348 View this thread: http://forums.slimdevices.com/showthread.php?t=28133 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
