Phil, See this post: Submitted by Miska on Sun, 02/12/2012 - 17:43 Here: http://www.computeraudiophile.com/content/Why-2496-not-24192
Which shows graphically what I mean. Upsampling should make a big difference to the smoothness of the waveform - if the data points are interpolated intelligently. I expect to see smoothed waveforms out of DAC. From a native 16/44 DAC (my befuddlement yesterday) I expect to see analogue smoothing. From a 24 bit, high sample rate DAC I expect to see smoothing due to the upsampling (and analogue smoothing at that finer level but this would not be resolvable probably). You keep waving this away but I think it's a reasonable expectation. Phil Leigh;695278 Wrote: > erm... the sampling RATE won't make any difference to this... I think it will (see above) Phil Leigh;695278 Wrote: > > Presumably they use 16 bits for this test to represent redbook CD > replay into the DAC.... > Kind of, except I don't think it's exactly equivalent (see further below). Phil Leigh;695278 Wrote: > > ....Had they generated a 24-bit -90dB sine wave file, the result would > have looked VERY different :-) > Yes of course and they did do that. That is figure 6. Phil Leigh;695278 Wrote: > > Just to be crystal clear on this, when Stereophile talk about the 3 > voltage levels... they ARE talking about the AC voltages: > zero-crossing, peak and trough for a single bit representing the sine > wave. They are NOT talking about anything to do with "jagged" DC ladder > steps or anything like that - because with one bit going on or off there > would only be 2 DC values anyway (on or off) and those values do NOT > EXIST outside of the DAC chip/IV stage/Filter... so they can't be > measured by putting any kind of test equipment across the analogue > output of a DAC. > regards > Phil No. They measured at the analogue output. Hence my initial puzzlement about no smoothing. Phil Leigh;695278 Wrote: > > I wouldn't want to speculate too much on how Stereophile created their > test data, but as you can't easily record a perfect -90dB sine wave from > any analogue source... (too much noise!) my guess is they generated it > as a 16-bit wav test tone mathematically on a PC, which is easy enough > to do. > I proposed what they did in my last post. Please have a read again carefully: darrenyeats;695256 Wrote: > > Now I realise when Stereophile tested the 16 bit undithered waveform, > probably they used a file at the highest sampling rate and bit > depth...just mimicking a 16 bit waveform within it. So the DAC doesn't > treat it to any upsampling goodness...the customer wants a crude > staircase drawn in hi-rez, the customer gets just that. > IOW I think they created this 16 bit -90db 1kHz sine wave mathematically and placed it in a 24/96 file. It is already at the DAC's native bit depth and sample rate so no interpolation is attempted. The DAC tries to play (as near as possible) a staircase shaped wave which, as we know, is impossible to do exactly. Had they played an actual 16/44 file of the same amplitude, I expect it would have been smoothed. Which is my point. Darren -- darrenyeats http://www.amazon.co.uk/gp/richpub/listmania/byauthor/A3H57URKQB8AQO/ref=cm_pdp_content_listmania/203-7606506-5721503. SB Touch ------------------------------------------------------------------------ darrenyeats's Profile: http://forums.slimdevices.com/member.php?userid=10799 View this thread: http://forums.slimdevices.com/showthread.php?t=94054 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/audiophiles
