darrenyeats;695256 Wrote: > Guys, here is where I was going wrong! I was thinking about that 16 bit > waveform and then I was thinking in 16/44 DAC terms (I was sleep > deprived!) which should smooth it analoguely. > > Obviously these DACs are not 16/44. But, even after getting some sleep, > this morning I would expect an upsampling 24 bit DAC to smooth 16/44 > digitally. > > 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. > Darren > > Sent from my HTC Sensation Z710e using Tapatalk
erm... the sampling RATE won't make any difference to this... 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. Presumably they use 16 bits for this test to represent redbook CD replay into the DAC. Had they generated a 24-bit -90dB sine wave file, the result would have looked VERY different :-) When a 16-bit file is presented to a 24-bit DAC - as we know from our Squeezeboxes - the "lowest" 8-bits are zero-filled (i.e. ignored). Therefore, the resulting test result waveform would look the same if the Benchmark was a 16 or 24 bit DAC... there's still only 1 bit "wiggling around in value". Actually, I can't see the point of performing this -90dB test on a real 24-bit DAC... not sure what they are trying to test. Surely they should be doing a -144dB test? In modern real-world terms this is meaningless because real-world 16-bit PCM streams are downsampled from 24-bit masters with dithering of some form or other which obfuscates the "problem" in the lowest bit by pseudo-randomizing its value. Bear in mind that no actual music files will EVER have consecutive sample values that look like part of a -90dB sine wave !!!!!!!. 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 -- Phil Leigh You want to see the signal path BEFORE it gets onto a CD/vinyl...it ain't what you'd call minimal... Touch(wired/W7)+Teddy Pardo PSU - Audiolense 3.3/2.0+INGUZ DRC - MF M1 DAC - Linn 5103 - full Aktiv 5.1 system (6x LK140's, ESPEK/TRIKAN/KATAN/SEIZMIK 10.5), Pekin Tuner, Townsend Supertweeters,VdH Toslink,Kimber 8TC Speaker & Chord Signature Plus Interconnect cables Stax4070+SRM7/II phones Kitchen Boom, Outdoors: SB Radio, Harmony One remote for everything. ------------------------------------------------------------------------ Phil Leigh's Profile: http://forums.slimdevices.com/member.php?userid=85 View this thread: http://forums.slimdevices.com/showthread.php?t=94054 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
