Andrew L. Weekes Wrote: > -The only plausible reason I can imagine for any audible difference is > that increased stress to the PSU affects the voltage or noise to the > clocks, which in turn produces jitter. Then again, I'm no electrical > engineer, and might be talking out of my ass.- > > You may not be an EE, but you are smart and logical ;) > > Andy.
He's on the right track. I'll explain why I think it's almost impossible that FLAC and WAV sound identical with onboard decoding: Remember that in digital equipment millions of voltage changes occur each second. All parts generate electromagnetic fields, radiofrequencies, causing a lot interference (EMI, RF). Measurments usually show total chaos. Even the most carefully designed equipment still has noise, interferences all over the circuit board(s) and even across equipment. Digital switching puts an aggressive load on power supplies, modulations are unavoidable. Even if all stages are separated and heavily filtered you can still see the digital 'ripples'. These interferences, signal injections and power supply ripples change the switching point (timing) of each bit, which is called jitter. Extremely complex patterns of timing errors (jitter) can be seen over a very wide frequency spectrum. Now all this noise and jitter isn't a problem at all as long as everything remains 'bitperfect', only for digital audio there's a more serious problem: bits have to be converted to analogue and the audio signal gets distorted when even the smallest amount of jitter reaches the audio conversion. It's not only the clock that gets infected, but the power supply of the DAC and the DAC directly by EMI, RF, remember that it's coupled with the rest of the circuit too (even when using a pulse transformer, etc.). There's no DAC which can do a jitterless conversion. Even buffering and reclocking isn't a solution, the process itself creates new jitter spectrum that is very similar to the original jitter spectrum, jitter is like a highly infective virus. I tried many jitter correction devices/solutions including masterclocking from the DAC, etc. but they don't bring the magic, the DAC keeps getting infected. That's why a very simple DAC can sound very good (my filterless, non-oversampling DAC sounds way better than the very expensive high-end DAC's I used before). That's also why many external superclocks and superregulators are not always the perfect solution, they improve some aspects but very often also introduce new problems. A properly implemented and carefully tuned simple design often sounds (and measures) best. That's also why good CD-transports are very expensive, it's impossible to get everything right from the optical readout (every correction adds jitter too) to the digital output. Onboard FLAC conversion has an effect on the jitter pattern/spectrum, but does it sound worse? The kinds of jitter which vary along with the music signal sound worse than random jitter. I can imagine the FLAC conversion causes a bit pattern which can be correlated to the music signal, so causing a jitter pattern which sounds worse. (Some designers actually listen to jitter patterns by connecting a small speaker, the correlation easily can be heard because the jitter noise sounds like the music that's played! (heavily distorted).) Some modifications on the SB2 will decrease jitter (not necessarily clock modifications). However because of the increased resolution it could be that the difference will be even easier to detect. Luckily there's the option of server side decoding. -- void _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
