Hi,
I've done this by using a Lehle Parallel and and Little Lehle. It works and is quiet, plus you can mix the amount of Eventide and non-Eventide signal (as I run a dry signal to my backline all the time, and switch the Eventide wet signal into the PA for a huge chorus, leads, fx etc). But I can also have a mix of Eventide and non-Eventide signal going to my backline as well. The Parallel allows you to mix it on the fly – or even switch out the Eventides (if something inexplicable like an endless delay occurs accidentally). If the PA option is selected, the backline feed swwitches over to non-Eventide. This preserves the balls of the sound, which gong stereo can remove – as I'm sure you know.
It's a 'tri-phonic' system. Hope this helps
