i have the rbi, and sorry, its actually a radial pedal, it had EFX and i misread it (its sideways standing up...) as ehx.
so i do have the fx loop.
Okay, that clears that up!
does the blend on the rbi blend the sansamp with the effects? i was under the impression that it was the input signal and sansamp, and the 50/50 switch would 'blend' the effect loop with the post sansamp signal.
From what I understand about it, you're right, and it should do exactly what you want (50% "clean" RBI, 50% effects). Volume-wise, you'll have to tweak your pedals and RBI as needed.
The only problem is, I'm not sure if it's a "typical" effects loop in the sense that it works best with rack effects, and not so well with pedals. Based on the RBI manual, it seems that it's meant more for rack units. However, it might work fine with pedals anyway, but it's going to be hit-or-miss in terms of whether or not your results are good. The higher output of the preamp could overdrive your effects. Of course, you can adjust levels to fix that, but then you might lose too much output for the running of a poweramp.
an alternate plan i had was splitting my signal with an aby before it went into the sansamp, running one to the sansamp, the other thru a distortion box, and into the return of the sansamp. will there be enough volume on the distortion for this? as it is instrument going into line (without the boost of the effect send jack)
With a normal effects loop, you wouldn't be able to do that - your preamp wouldn't work; only the signal at the "Return" jack would. But the 50/50 mix thing on the RBI has me intrigued... maybe it could work, since it's routing 50% of the signal around the loop? Honestly, I don't know what the results would be. You'd have to try it out....
IMO, if both of these options we discussed do work, you're definitely better off with the first one; the ABY switch and your routing idea present a wealth of extra problems. It's far easier to adjust your preamp level and effects pedal levels to prevent overdriving your pedals, than it is to use the ABY switch idea.