> > Mark, > > Thanks, your message did indeed suggest to me a way that using different > sound cards for input and output makes things more complicated for the > sound system. Only if the input analog-to-digital converter (ADC) and > the output digital-to-analog (DAC) use the same clock, will the number > of input samples available for reading match the number of output > samples that should be written, over a given span of time. If there are > two clocks, one will be slightly faster than the other. If some sound > processing application is in a loop of reading X number of samples, > processing them, and then writing X number of (different) samples, > eventually the faster interface has to wait for the slower one to catch > up. Waiting means lost samples, and lost samples sometimes cause audible > clicks or pops. > Paul, You're completely on top of the problem now. The 'normal' way to get around this problem. as Steve suggested earlier, is to use a common clock. This is not necessarily impossible with your cards, but would take some work. At the studio level there are fancy, expensive clocks, like 'Word Clock', but that may not be necessary for your application. The 9636 has a s/pdif output. s/pdif carries a clock. Many Sound Blaster boards have s/pdif inputs. Since s/pdif carries a clock, if you can configure the Sound Blaster to use s/pdif as it's clock source, and you hook a cable from the s/pdif output on the RME to the s/pdif input on the Sound Blaster, then conceptually they will both run locked together. I have done this with my Digi 001, RME HDSP 9652 and my RME 9636, all operating under Windows where I have drivers and configuration tools that allow control over this sort of thing, but using the ADAT path instead of s/pdif. It works well. Unfortunately, Linux configuration tools are not always supporting all the features of different cards, so you would have to figure out whether this stuff would work for you. Thomas recently did a little app called hdspconf which allows you to set the clock source on the RME card. This could work for you if you used the Sound Blaster as the master and the RME as the slave. I noticed some funny effects when doing this myself, so I think you'd just have to try it yourself and see how it goes. So, I think there may be solutions if you're willing to dig in a bit. Good luck, Mark
