ccaudle wrote: > Switching supplies can make life hard. Assuming a reasonably modern > switcher the basic switching rate would probably be somewhere around > 100kHz-200kHz, with harmonics extending into a few MHz assuming it is > switching with fast edges to improve efficiency. The basic switching > rate would probably fall into the right range that if it modulates the > clock, the lower modulation sidebands will fall in the middle of the > audio band. The DAC probably has 0dB PSRR at those frequencies, so any > of the noise that is not completely filtered from the DAC power supply > causes AM of the output, potentially PM on the output if the power > supply noise modulates the clock input switching threshold, and > potentially direct PM of the oscillator if the noise gets on the > oscillator power supply. Just painful all around. Would be interesting > to figure out how much filtering would be required to get any power > supply noise effects reduced to inaudible. What kind of noise amplitude > and spectrum is on the output of that supply? > > -- Chris C
Actually the regulators I'm using have 60db PSRR out to over 3MHz. The clocks and DAC chip have separate regulators. I haven't done a full analysis of the power at different points (haven't had the time!) I should do that soon. John S. ------------------------------------------------------------------------ JohnSwenson's Profile: http://forums.slimdevices.com/member.php?userid=5974 View this thread: http://forums.slimdevices.com/showthread.php?t=97881 _______________________________________________ discuss mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/discuss
