Alan Cox <[email protected]> writes: > If it's electrical noise though then power fluctuations or similar > could be to blame ? To check this, I've dusted off my old oscilloscope. I've used speaker-test program to generate a 500, 900 and 1000 Hz sine wave that I've sent on the spdif line (as PCM) and had them decoded by my Yamaha DSP-A1 amplifier. I've enclosed only the snapshots to this mail, I hope it'll get through vger's majordomo. Anyway, the oscilloscope shows that: - a spike occurs every 330 useconds (about 3kHz) (note: 330us is 15.85 times the period of the 48KHz spdif stream) - the spike level roughly matches the level of the sine waves 330 useconds sooner I may be wrong, but it looks like that, somewhere in the audio data stream, a buffer is read downstream before the correct value is written by upstream (delayed by SATA I/O ??). OTOH, 16 samples is a very short buffer... If needed I can try other things like: - loop back the spdif output to my mobo's input to get the actual values of the PCM stream sent to the Yamaha. - try the oscilloscope on the analog output of the SB live card ( I couldn't hear any distorsion on the analog line, but it does mean there no problem on this side as the D/A converter may filter out these kind of short duration spikes) - try another signal shape Any thought ? HTH
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