On Oct 6, 2007, at 3:01, Magnus Danielson wrote: >> >> If the sample rate is 44.1 kHz then the adev below 1 s, even >> down to 10 us, or jitter, or the phase noise above 1 kHz are >> they key parameters; not long-term drift. In this case I'd take >> a nice 10811A over a typical Rb any day. Does anyone know >> for sure, or am I off base here? > > No, I meant to say the same. The phase-noise in the 10-1000 Hz > region is > surely what will mostly affect the sound, so we are looking at side- > band > phase-noise rather than Allan dev plots. However, slow modulations > even up to > a minute is known to be perceptible, but the tolerance levels is > not flat.
I think this is correct. Is there a figure in dBc/Hz at say 10, 100 or 100 Hz. When measured with a Wavecrest 2075 there is a clear difference in hearing between an oscillator with -100 dBc and -96dBc both at 10Hz. The listening difference is in the sound stage accuracy and acoustics of the concert hall. I do not have (access to) instruments that measure phase noise directly to say -120 dBc at 10Hz. > If anyone is interested in learning about serious reasoning behind > acheiving > high dynamic digital audio, look up Julian Dunn, who has written a > few very > good papers. He also did work for the AES/EBU jitter limits and > also wrote some > stuff for Audio Precision. Great stuff and a sensible reasoning on > these > things. Agreed, but Julian does not give phase noise figures in dBc/Hz figures. > It should be noted that for lower modulation frequencies, the side- > band will > be so near that the ears masking-effect will cancel it out unless > it is > strong, so tolerance levels rises for lower frequencies. I doubt if this is true. I have never found an agreement to known psycho-acoustic masking figures and own jitter measurements. It is amazing what can be heard with jitter values of pico-seconds. There must be a relation between these low values and something else, but I am not aware of it. The phase noise statement of Magnus can be correct, I think it is, but the side bands resulting from these values are within the masking curves. Experiments with a modulated clock show that large modulation can not be heard. However, noise modulation much smaller can destroy the sound stage. I am very interested in a good explanation of this. I you do not believe me you are welcome for a demonstration. Henk _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.