After reading several threads discussing how jitter, flac or wav formats and 63dB tweaks may affect the analogue output connected to the SPDIF of a squeeze box I was intrigued enough to do some of my own tests. Using a 16-bit stereo 44100 Hz PCM wav file (The Disappointed by XTC), a slimserver 6.3.1 on SLES 9, a wireless Squeezebox 3 firmware 55, a cheap 5 metre optical cable, an Audigy ZS Pro on windows XP using goldwave to record the squeezeboxs optical output back to disc, sox, od, flac, md5sum and the black magic of awk, I observed the following results:
1. Encoding the wav file to flac then decoding back to wav produces identical PCM to the original wav file (as expected). 2. Playing the wav file from slimserver over the wireless network, out the Squeezeboxs optical output with fixed digital volume, 0 dB analogue attenuation, into the windows PC and recorded to disc produces identical PCM to the original wav file. I repeated the song 5 times and didnt find a single bit error. 3. Playing the wav file from slimserver with fixed digital output, 63.0 dB analogue attenuation produces identical PCM to the original wav file. 4. Playing the wav file from slimserver with variable digital output at full volume, 0 dB analogue attenuation produces identical PCM to the original wav file. 5. Playing the wav file from slimserver with variable digital output at full volume, 63.0 dB analogue attenuation produces identical PCM to the original wav file. 6. Playing the wav file from slimserver with variable digital output at half volume, 0 dB analogue attenuation produces different PCM to the original wav file. 7. Playing the flac file from slimserver with fixed digital output, 0 dB analogue attenuation produces identical PCM to the original wav file. The results suggest to me that optical SPDIF is a high quality transport. Even my (£75) test system is unlikely to transform the PCM data in a manner that is continuously audible (tweaks or otherwise). Of course, whatever happens to the PCM after it leaves the SPDIF receiver is another matter (I havent tried the coax cable yet, or Willie Nelson's "Georgia", which I should). -- ohios ------------------------------------------------------------------------ ohios's Profile: http://forums.slimdevices.com/member.php?userid=6807 View this thread: http://forums.slimdevices.com/showthread.php?t=26436 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
