> Hmmm.. if Wadia is good with capacitor coupling at their price point, it > makes you wonder why anyone is spending for transformers. AFAICT the > waveforms are identical at these frequencies... can anyone shed some > light?
Without seeing the full Wadia circuit, it's hard to be specific, but very few (even expensive) products have a well-designed SPDIF circuit - one reason for using a (good) transformer is is makes it easier to acheive a wide-band, purely resistive, 75R match, which is critical for good SPDIF performance. The SB2 for example can *never* be a true 75R resistive impedance, since the phono socket, for one, prevents it from ever being so, it causes an impedance mismatch, which will cause reflections on the SPDIF transmission line. That said, most devices with a transformer don't acheive a good match either, for a number of reasons, like transformer choice, lack of proper testing and engineering etc. This seems to be critical for optimal SPIDF performance and is in the realms of RF engineering rather than audio. One needs to use Time Domain Reflectometry (TDR) to see the reflections in the line, that come from the mismatches inherent in most setups - eliminating these (by proper, wideband, impedance matching) works wonders. Andy. -- Andrew L. Weekes _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
