SuperQ;553493 Wrote: > My vote is it's all in their head. There is a theoretical audibility of > clock jitter (which is improved in the Touch). But nobody has been able > to demonstrate this in any repeatable way that I'm aware of. > > It would be really interesting to put a Touch and a Duet in your system > and use Audio DiffMaker (http://www.libinst.com/Audio%20DiffMaker.htm) > to measure the analog output of your DACmagic. In theory there may be > some difference, but DiffMaker will prove it.
You have to be very careful with ADM for jitter issues. You have to make sure that the jitter of the clock feeding the ADC you are measuring the signal with has significantly lower jitter than the playback system you are trying to measure the jitter of. This is NOT a slam dunk. I have measured the ADC clock jitter of a number of different sound cards and external systems (firewire and USB) and have not found anything lower than 50ps. Most are much higher. One of the most favored pro firewire boxes has an ADC clock jitter of 700ps, another had 1200ps. I hope its obvious that trying to use ADM to measure the output of a DAC with an ADC whose jitter is 10 times greater than the jitter differences between different transports is an exercise in futility. I AM also one of those who can hear significant differences with fairly small changes in jitter. I have done an experiment where I have taken a stock SB3 and replaced the clock oscillators with ones that have been measured on the very expensive systems to have about 3 times lower jitter than the stock ones. The analog outs sounded significantly better with this change. Nothing else changed. Blind comparisons between this modified SB3 and a stock SB3 were done with several people and most could reliably tell the difference. One person couldn't. Its far stickier with S/PDIF out. In this case the DAC chip(s) are getting fed by a clock which can be generated in many different ways and have wildly differeing sensitivities to jitter and reflections of the input signal. Because one DAC seems to not have a difference between a Duet or a Touch does not mean there is no difference and it does not mean that no DAC will see a difference. It depends very much on the implementation of the DAC. BTW just because a DAC is fairly insensitive to input sources does NOT mean it has low jitter. For some reason there is the perception floating around that a DAC with low input sensitivity is automaticaly a very good DAC. This is not necessarily true. There are several methods for decreasing jitter sensitivity which actually produce fairly high levels of jitter themselves. Yes it doesn't matter what the source is, they will all sound the same: uniform mediocrity. A number of people have given me DACs to look at and in several cases I have found souch circuits. I have bypassed them. You now have a DAC which sounds much better with really good sources and terrible on lousy sources. A LOT of DAC manufacturers have gravitated towards the "make everything sound pretty good" approach, but that limits the performance when fed by a really good source. Unfortunately no manufacturer is going to TELL you that! All that is to say that the reports of some people saying they hear no difference and some saying they hear big differences are perfectly expected, if everybody said there was no difference or everybody said there was a big difference, THAT is when I would start wondering. John S. -- JohnSwenson ------------------------------------------------------------------------ JohnSwenson's Profile: http://forums.slimdevices.com/member.php?userid=5974 View this thread: http://forums.slimdevices.com/showthread.php?t=79500 _______________________________________________ Touch mailing list Touch@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/touch
