On Tue, Nov 19, 2013 at 12:21 AM, Fons Adriaensen <fons@linuxaudio.org> wrote:

It's perfectly possible, and without any signficant loss of quality.
Jack is configured to use one of the cards. The others become clients,
and their signals are resampled to match the rate of the 'master' card.
Zita-ajbridge will do this with a constant and repeatable latency. This
is also reported to Jack, so smart applications can compensate for it.
Remaining delay variations will be around a microsecond (with decent HW)
and be very slow.

Right. I've used Zita-ajbridge, which I guess is what Ralf was thinking of, for this purpose. It works extremely well. I also use ADAT sync when needed to sync between two machines. I clarified with Jason off-list so as not to detract too much from the thread about getting the zoom to work, but it came across to me that he was saying there would be no problems at all to use multiple devices without *any* kind of sync solution. Which, as he himself clarified, is not true.