-And, of course, can you hear a difference in the output of the SB2? (Could you pass a blind test? ;)-
I'm confident I could, although I haven't tried a blind test. To me the SB" with the standard PSU is edgy and tiring after a while, whilst the linear PSU makes it far more listenable, but obviously lacking in comprison the the CD player. I've just pulled a pair of super reg's from something, that I can easily convert to 13V or so, to try isolating the audio supplies further, as Sean has mentioned in a number of places. Tha aim being to feed in an external 13V to replace the internal mutliplier-derived supply from the display, although this isn't -that- noisy as it's quite easy to filter, as it contains little HF energy like many capacitor-only voltage mutlipliers. This is the first line of attack, but I have reservations that the fundamental limitations lie in the clocks at present - the oscillators run from a switcher, not a linear PSU and the two Pierce reference oscillators are sharing a single chip, which further exacerbates the jitter problems, based on experience. I really need to re-box it to make space and gain access to try and address these areas in order to evaluate the differences, I have a nice 1U 19" case to do this, just need to persaude the guys at work to do some CNC work for me ;) I've also re-configured the output stage from a single-pole filter to a 2-pole Bessel, to try and help reduce the supersonic stuff at the output further, but I'd like to see more suppression - running a sweep on the SB2 you can see the aliasing products from the supersonic output folding back on the analyser - a Bessel was chosen as it has the best transient performance, but this is at the expense of ultimate attenuation, I'd need more poles ideally, which is impractical as-is. TI recommend a 2-pole Butterworth, but I'm far from convinced this is adequate, given the performance of the DAC's own internal analogue filter. Andy. -- Andrew L. Weekes _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
