[Ardour-Users] how do I set up two USB soundcards?

[Kim Cascone]

I posted a couple of weeks ago looking for a four channel USB sound card 
that worked on Linux
but then it occurred to me that I could possibly use two stereo USB 
cards to construct a single four channel output

I was able to do something similar in OS X a few years ago which is 
called creating an "aggregate device"

thinking I could do the same with ALSA/Jack
I Googled and found a couple of old posts on Ubuntu forums
but the explanations weren't all that clear

so I plugged in two iMac USB soundcards into my laptop
and was able to see them in the Jack ctl panel under "Output Device"
yet only one writable client "System/playback1/playback2" showed up in 
the Connections panel under System

can someone explain how to connect to two soundcards at the same time in 
Jack?

I do have jack_in and jack_out

I'm posting this on the Ardour list because I know how tightly 
interwoven the Ardour and Jack communities are
and that often times Ardour gurus are also Jack gurus

any help is greatly appreciated!

ciao!
kim