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. -- JohnSwenson ------------------------------------------------------------------------ JohnSwenson's Profile: http://forums.slimdevices.com/member.php?userid=5974 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
