Phil Leigh;494790 Wrote: > If you do this test it will probably produce 19-25 dB Nulls - not > great. > However, this is not the whole story. Open the difference file in > Audacity (or similar) and look at the frequency spectrum plots. You will > find that actually the difference is more like -50dB, but with large > differences at the low end of the spectrum (<100 Hz) which is skewing > the result. > Also you will see that ADM cannot compensate for the SB clock drift and > you can still hear (bits of) the music. > > What does this mean in practice? > > To improve playback quality and getter it closer to the original CD, we > must: > > 1) use an external DAC with a better clock and more accurate > (frequency/phase response/noise) analogue stage - ideally use a linked > clock so that the DAC can drive the SB - this requires mods to DAC and > SB. > or > 2) put a much better (more stable/accurate/low noise PSU) clock in the > SB and mod the analogue stage to improve its transient and self-noise > performance - presumably the SB+ already does this? > or > 3) upgrade to a Touch or TP which have better clocks/outputs stages and > which measure better in this test (well, the Touch certainly does, > others are looking at the TP as I don't have one). > > IMO Most of the "problem" lies with the analogue stage of the SB3. > Those electrolytic caps can't be helping here and the driver IC can > surely be improved?. Not sure what an SB+ looks like in this respect.
Hi Phil, Your findings re the clock drift below 100Hz confirm what Pat at AR-T has been pounding into me for months. A quiet clock is critical to getting correct playback. The trick is what he means by "quiet". What he means is low noise below 100Hz. Actually his target is below 1Hz. I believe the correct term is reduced flicker noise (1/f noise)? Even if one has a high quality XO it will be noisy below 100Hz unless the PS is designed specifically to reduce 1/f noise. Interesting how your results tie into what I'm finding whist ditzing with the Duet receiver. Injecting a clean clock made a huge improvement in the SQ - far more than all the cleanup work I did on the DAC analog outputs. My guess is a low 1/f noise PS for the DAC chip would help below 100Hz, too. Again, apologies for jumping in here... Pete -- Pete Fowler ------------------------------------------------------------------------ Pete Fowler's Profile: http://forums.slimdevices.com/member.php?userid=20270 View this thread: http://forums.slimdevices.com/showthread.php?t=71321 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/audiophiles
