Can I record a Martix Mix to SD Card

Can I record a matrix mix on one of the stereo busses to SD Card.

When we are recording church services, we normally have a slightly different mix going to the recorder. The mix is normally the main PA mix, plus a pair of ambient mics which are faded up and down to capture the congregation singing. In most installs, I have a small 4 chael "recording mixer" next to the main desk. This takes the main desk record output, and the ambient mics and feeds this to a field recorder (zoom, tascam, etc.).

I was thinking that using the "matrix mix" i could create the recording mix internally on the Sutudio live desk (the matrix would be the main mix plus ambients that I can fade up and down), but is there anyway I can recod that to the inbuilt SD recorder?

I only seem to be able to select inputs 1-32 and/or main mix bus for the recorder.

I guess the other option would be to do the matrix mix, but just output that to a separate recorder (which would be a shame).

Thanks.