Would this work (Passive Mixer)

[mgrEIGHT]

I was going to post a schematic but i have no place to host it so i'll explain it the best i can. This is for mixing two preamps with the same power amp.
Each input goes to its own isolation transformer, the secondaries of each transformer go to a pot to ground volume control. the middle lugs of each pot meet together at a master volume that goes to the poweramp.
So would this work or am i overlooking some basic electroncics principal or something?

[mgrEIGHT]

The only reason i want it to be passive is because i thought it would clip massively if i powered it with a 9v battery