AlexM wrote: > About a year ago I replied to the TT3 thread with some measurements > comparing CPU utilisation in the Touch at 16/44 and 24/96 with and > without server-side FLAC decoding. For my tests, I used a wired Ethernet > connection. CPU utilisation was measured simply by connecting via SSH > and running 'top' > > I don't have the exact figures to hand, but IIRC at 16/44 the difference > was something like 10% (via FLAC) vs. 30% (PCM to SBT), and at 24/96 it > was (55-65% vs >90%). I couldn't detect any beneficial effect of > streaming PCM, but this did establish that the theory supporting > improved SQ with at least this component of TT3 mods was a bust. > Unsuprisingly nobody could think of a reason why more CPU utilisation > would be better, especially since the theory was based on the opposite > being true. Suprising that nobody bothered to check before, especially > as it was so easy to do. > > Ah.. here we go.. found my tests on a different board - > http://theartofsound.net/forum/showthread.php?t=15594&highlight=Touch+CPU&page=8 > > Archimango - excellent work on the tests BTW. I also have a Emu 0404 > USB, and have long been telling people what a cracking interface it is, > especially for the money!. Your figures do show it to be a very > transparent device for A/D. You have inspired me to do some testing of > my own to optimise the noise performance of my system. > > Cheers, > Alex
Thanks for the note Alex! Glad to see another 0404USB user :-). Let me know if in your testing you find a good way to measure JITTER! Good point about checking on the Touch's CPU utilization. This AM I logged into the Touch and ran 'top -d1' to check CPU usage every second while playing music. I chose Prince's 'Batdance' since I had a good 24/96 vinyl rip as well as the original 16/44; I figure a dynamic track like this could give the Touch's FLAC decoding a nice work out. This is with my Touch running default EDO firmware settings, ethernet connected. For MOST of the time, the CPU use looks like this: 24/96: FLAC level 8 compression: 20-30% default view, 70-85% peak with spectrum analyzer 16/44: FLAC level 8 compression: 15-25% default view, 65-75% peak with spectrum analyzer Clearly turning on the spectrum analyzer "Now Playing" view eats up CPU cycles significantly more than just the playback itself from what I see. About a couple of times over the 4 minute song, the jive_alsa process wakes up in a big way and this pushes CPU use to 90-100% for about 5-10 seconds. I believe jive_alsa runs at realtime priority level and there's a discussion about it elsewhere. Whether this changes sound quality, I dunno. SO even though I couldn't find any sonic change going the way of TT3 with turning off the screen and everything, I wonder if doing the opposite - stressing out the CPU with 24/96 FLAC + spectrum analyzer view running during playback lead to stuff like increasing noise floor... Maybe I'll give this a try tonight. ------------------------------------------------------------------------ Archimago's Profile: http://forums.slimdevices.com/member.php?userid=2207 View this thread: http://forums.slimdevices.com/showthread.php?t=97950 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/audiophiles
