> A while ago I had a very similar problem, on an Athlon XP desktop machine. > Whenever I ran jack at low latency, there was a high pitched noise coming > from somewhere inside the case. I was unable to pinpoint where exactly it > came from, but I'm pretty sure it originated somewhere on the mainboard, > maybe the CPU or the PCI cards. > But it didn't just come from the case, it was also audible on headphones, > on both my PCI sound cards! This is EXACTLY the problem I faced, and EXACTLY the response I had to it. Where the hell is that faint hum coming from? What was especially confusing is that it was audible both without headphones, very slightly, and with headphones, amplified. > At 256 frames/second, the noise was barely audible... At 128 it was quite > easily noticable, and at 64 it became downright annoying. At 32 or 16 > frames/second it was even worse... This is exactly the behavior I experienced. Very slight at higher latencies; however, I tried it at my friend's club and over the high-powered amps it is still a clear annoyance, not to mention not being able to sing and run effects over it at low latency. > But the most intriguing part of the whole story: Not only did the noise > get louder at a lower latency, it also seemed to precisely double its > frequency when running at halve the number of frames. I even tried to > measure the frequency of the noise. As far as I remember, when running > jack for instance at 44100Hz, periodsize 32, the noise was at exactly > 44100/32 = 1378Hz! That is absolutely fascinating. I WILL investigate this; if it coincides, we have a VERY strong case that this is the same problem. > Anyway, this whole issue went away after I disabled athcool (a utility to > reduce heat and power consumption on Athlon CPUs) while running jack. But > still all of this remains a mystery to me... What would be the corresponding utility for a Pentium 4 mobile (used before centrinos, slightly modified for notebook assemblage but still a full Pentium 4) be? How could I completely de-activate power management and open the case and put some ice cubes in? (IE manage power myself, with a room fan, or liquid cooling, or whatever...) Carlo
