Dominique Michel wrote: > Upsampling does nothing for analog reproduction because you cannot get more > informations that what you get from the DAC output. Upsampling is only a matter > of cost: > > higher the ADC frequency, cheaper is the output filter for approximately the > same analog result at the output. It's not simply cost. It's a balance: less upsampling means you need better analogue filtering for the same results. The best analogue filtering you can make with the best available components (for any cost) is not necessarily as good as some digital upsampling before the DAC. > Most (all?) cheap DAC convert the PCM linear into Pulse Width > Modulation or better into delta-sigma modulation because the output > filter become the cheapest of all: a simple RC low-pass filter. See > http://en.wikipedia.org/wiki/Digital-to-analog_converter Delta-sigma is theoretically lovely. It's good upsampling taken to an extreme, allowing the analogue stage to be simple due to a better digital stage shifting the distortion to a place where it doesn't matter. But for good 24-bit output at high initial sample rates, because the DACs can't output accurately enough at the insanely high frequency you'd need for a delta-sigma and a simple RC filter to be good enough, you need good analogue filters still, hit physical limitations in quality, and need more complex digital upsampling than delta-sigma for good results. -- Jamie ------------------------------------------------------------------------------ _______________________________________________ Alsa-user mailing list Alsa-user@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-user
