JohnSwenson;571006 Wrote: > I've already posted my thoughts on this subject back towards the > beginning of this thread but I'll restate them here. > > It seems to me there are two parts to this debate: 1, can people hear > it. 2, is there a measurable mechanism that can account for it. > > In regards to 1: > > I CAN hear a definite difference between decoding FLAC and PCM on the > Touch through its analog outs. I HAVE done blind tests and can still > detect the difference. Some people have chimed up and said that these > are scientifically useless tests and are thus meaningless. To which I > say, please post an officially sanctioned protocol that IS valid and I > will be glad to take part. I am NOT an expert at such testing and don't > know what constitutes an acceptable test. It seems to me that the people > that insist on such tests are the ones that are responsible for > providing the terms of such a test. Where are they? > > On 2, one possible mechanism is jitter feeding the DAC chip. I do have > some equipment that can be used to measure jitter, but its not super > sensitive. The jitter in the Touch is just below the level of what my > equipment can measure. With this setup I cannot measure a difference > between FLAC and PCM decode, but that is not conclusive. I need a more > sensitive jitter analyzer for this test. When headphones are plugged > into the Touch I CAN see an increase in jitter above the threshold of > my equipment, so it IS possible for the jitter to change in the Touch. > (it doesn't mean decoder differences affect jitter, but it does say > that something going on inside the Touch can change the jitter) > > There are much more sensitive jitter analyzers, but they cost $35K to > $50K and I can't afford that. If anyone wants to donate to the cause I > will be glad to accept a donation or loan of such an instrument to make > the tests. > > Another test being performed is Audio Diffmaker. This sounds like it > should be a perfect test. The problem I have is that the AD converters > being used for the testing have several times the jitter of the Touch. > How can you hope to make a valid test of the affect of a small jitter > change on a waveform when what you are using to sample that waveform > has jitter 10 times greater than the what you are trying to measure? If > someone has an AD converter with a 10ps jitter or less sampling clock > that would be a MUCH better instrument to use. I could build one, but > again that takes money I don't have. > > So there you have my stand, I'm convinced that I can hear the > difference between FLAC and PCM decoded on the Touch (via wired > ethernet) on the analog outputs. As of this time I have not been able > to measure anything electrical that could be causing this. BUT I don't > think I have the proper test equipment to to do a decent job of > measuring it if it does exist. > > John S.
I think John has put his finger on an important point here! - It reminds me of college physics. Specifically the "Heisenberg uncertainty principle". Sometimes when you try to observe/measure something you cant help but change what it is you are trying to observe/measure! Hense - some things are inherently unmeasurable. - probably all bs, but its fun to think about! -- earwaxer9 System: modified Winsome Labs Mouse, modified Maggie MMG's, Transporter, HSU sub 12, MSB DAC to 500 watt sub slave amp, JPS labs power cords, Silver audio interconnect, Audioquest Granite speaker cable. ------------------------------------------------------------------------ earwaxer9's Profile: http://forums.slimdevices.com/member.php?userid=39527 View this thread: http://forums.slimdevices.com/showthread.php?t=71321 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
