On Sun, Dec 23, 2012 at 01:07:19PM -0500, Joe Hartley wrote: > http://xkcd.com/285/ > > I've always had fine results running my Delta1010s at 44.1kHz, since I > only do audio destined for CD and wanted to avoid the re-sampling. > Why would running them at 48kHz make them perform better? The usual combination of technical and economic factors. Every AD or DA needs an anti-aliasing filter. Say you want a flat response up to 20 kHz, and at least -120 dB at half the sample rate. At 44.1 kHz that means roughly -60 dB/kHz, at 48 kHz -30 dB/kHz for the transition band of the filter. Now the complexity of an HP filter (the number of coefficients) is proportional to those numbers. That means that for the same specs at 44.1 kHz you need twice the number of gates, chip area, power etc. as at 48 kHz. That is a simplification, if you take everything into account the ratio is even bigger. This, plus the fact that 44.1 kHz is considered to be a 'consumer' rate anyway means there is a strong incentive for AD/DA chip designers to cut corners at 44.1 kHz. And that is exactly what happens in almost all cases, with very few exceptions. The alternative, which makes sense, is to forget about HW support for 44.1 kHz and let the driver resample from 48 to 44.1 if the user wants to use that rate. This is also valid for higher sample rates. At 96 kHz, assuming you want a flat response up to say 32 kHz, you only need 7.5 dB/kHz. Since the _delay_ of the filter is also proportional to the transition band slope, such a filter can have much less latency than at 48 kHz, and that's the reason why e.g. digital snakes and mixers designed for PA use operate at 96 kHz. Low latency is essential for PA, in particular if in-ear monitors are used. Ciao, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow) _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
