Bruce Griffiths wrote: >> Tom >> >> >> The major source of interchannel phase shift instability will be the >> phase shift instabilities of the sound card input RC coupling network >> particularly if electrolytic capacitors are used and the input >> frequencies are too close to the high pass RC filter 3dB frequency. >> Amplifier phase shift instabilities are much smaller and the >> interchannel group delay mismatch will be relatively small as the group >> delay for each channel is determined by the digital filters used by the ADC. >> >> >> > For temperatures around 20C a wet electrolytic cap has a tempco of aroun > +500ppm/C or so. > With a 0.5dBinput frequency of 20Hz a typical sound card has a high pass > filter input time constant of about 33ms. > At 1kHz the corresponding phase shift is about 800ns with a tempco of > about 0.4ns/C. > > Bruce > Correction: The time constant should have been 22ms and the phase shift 1.16us with a tempco of 580ps/C. Since both channels have the same nominal low frequency cutoff the differential phase shift tempco will be somewhat smaller.
Bruce _______________________________________________ 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.
