marcoc1712 wrote: > John, > > > could I ask You witch USB DAC are you using? If is kind of a KIt or a > commercial product, could you point me to the source? > > is a kind of the one you'll be using in CSP1? > > thx a lot. > > p.s. > > I could not understand why if you upsample at i.e. 352.8 you still need > a software filter, is not assured this way that aliasing is far away > from the audible spectrum (reason why the hardware filter is disabled, I > suppose)? > > > Marco.
The DAC I am using is a custom design I have done so you can't get it anywhere. Speaking of kits, I am designing a somewhat similar DAC for Bottlehead, it will be a kit, but all the hard work is already done on one PCB. It's not available yet, but hopefully will be out sometime early next year. Or just get a CSP! As to upsampling, all (usefull) upsampling has to use a filter, that is just part of the upsampling process. If you just resample the data without applying the filter you haven't actually done anything. This is best with a picture, I don't have one handy (I'm on vacation), maybe someone else can post a picture of this. For the wordy explanation, lets take the output of a basic DAC chip, without any digital or analog filtering you get a stairstep. Upsampling without the filter is just subdividing each of those stairsteps into smaller pieces, but keeping the same values. Lets say you have a sample at .5V level, 8X upsampling gives you 8 shorter samples all at the same .5V, you haven't changed anything. What you want is the upsampler to make a "guess" at filling in the intermediate values between the .5V sample and the next sample. The filter defines exactly how that is done. The human hearing system seems to be quite sensitive to exactly what that filter does, slight differences in that filter can make significant differences in what we hear. All modern DAC chips do this filtering process builtin to the chip, and every one of them does it in such a way that does not sound so good. This thread is all about doing that filtering externally in order to bypass the not so good version in the DAC chip. John S. ------------------------------------------------------------------------ JohnSwenson's Profile: http://forums.slimdevices.com/member.php?userid=5974 View this thread: http://forums.slimdevices.com/showthread.php?t=99088 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/audiophiles
