There is a problem with using digital interfaces like SPDIF. Unlike analog where you can just plug them in and have it work, when you use a digital interface you must also engineer a way for all devices to work from the same sample rate clock. If you don't do this you will get pops and clicks as the devices get out of sync. So unless all your devcies have a word clock input and you have a way to distribute clock to all of them it doesn't work. This is why you don't see SPDIF mixers because there is no easy way to solve that problem. This also limits you to only work at a sample rate all the devices can do.
For this reason digital interfaceing only works well with two deivices at a time. The sound card is one device and the preamp is the second device. Because SPDIF is single direction this means if you only connect the SPDIF out of the preamp to the SPDIF in of the sound card the sample rate clock in the preamp has to be the master and you have to set the sound card to get clock from the preamp.
So, unless you spend a lot of money and do a lot of engineering you can't use more then one SPDIF device at a time.
Big studios that try to use more then one digital device have a rack mount unit that does nothing but word clock and it has many word clock outputs on it for all the digital devices like the digial mixer, outboard converters, effects, synths, recorders, etc. Even with this expensive setup you run the risk of errors in the system. Unlike computer interfaces all digital audio interfaces SPDIF, AES/EBU, ADAT, TDIFF, etc are non error checking and single direction per wire. So if have errors there is no way it can correct them or resend samples. You may not even hear the errors most of the time but they are there.
So analog is the way to go if you need more then two connections. If you need better quality upgrade your sound card to a Lynx that has high quality converters and balanced analog inputs.
post edited by ohhey - 2005/10/11 11:05:08