[brucek]

I suppose as long as you assume that the response of the line-out 1/4" TRS to line-in 1/4" TRS loop is the same as with the XLR mic input, then there's no reason you can't use the left channel loopback cal method. The individual channel sensitivity adjust would allow for getting your levels correct to pull that off.

It's verifiable by taking a soundcard cal test of (1/4" TRS line-out to XLR) versus (1/4" TRS line-out to 1/4" TRS line-in). If they match, you're good.

brucek