Now that I have the MuRF & Phaser, what is the best way to use the stereo outputs from each unit simultaneously?
Do I use a small mixer to do the job or will a Wye cable suffice to merge the 2 lefts & 2 right signals together?
Additonally, with whatever method is used.. what about downstream mono effects? Should I Wye together the Left sides from the stereo units together & feed only the Lefts to the downstream mono effects?
I’ve had the same problem with the few stereo Boss pedals & noone seems to have the right answer.
Firstly for downstream fx, if you only use the left side, and you have the MuRF on you will loose one half of the sound… but if both are off, then yes you will need to blend the two mono out sides together.
Note I said Blend.
You shouldn’t 'y" them together due to differing impedance values, you should use a mixer to blend them back together. Also with a mixer, you could probably come up with some way of blending the stereo sound into a mono cable for down stream fx… although I don’t know if the phaser cancels itself out since one side is the opposite of the other…
I would suggest running the outputs of the 103 & 105 into a stereo mixer with an fx loop, then place any mono fx in the loop, and lastly to the 2 amps or second mixer
If you run both channels through a single aux/return, you will lose your stereo image as the signal sums to mono. You might get away with a partial blend (of stereo effects and mono effects on a “loop”), but that might not be the effect you are after. If you only route one channel through the aux you are basically where you were without the mixer.
My advice is to put your stereo effects at the end of the “chain”. For example, my reverb and a digi delay are both stereo, so they go at the end. I’ve got stereo filters (MFC-42, Electrix Filter Queen) and two ring mods .
You can use mono inserts on some stereo instruments. The Voyager, Rhodes Suitcase and Rhodes Chroma are like this
Also with a mixer, you could probably come up with some way of blending the stereo sound into a mono cable for down stream fx… although I don’t know if the phaser cancels itself out since one side is the opposite of the other… 
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