Small audio transformers?

I'm thinking about a couple projects requiring small audio transformers. One would be a splitter to drive two guitar amps, with two transformers providing isolation against ground loops.

The other would a passive direct box, built into a small pedalboard for my acoustic. This one would need to provide the impedance match to a Lo-Z PA mixer as well as isolation.

Anyone have any recommended models & vendors for such things?

Check out Weber's transformer page.
http://taweber.powweb.com/store/magnetic.htm

It's the very last link for a balun transformer "WBALUN". I've used them for both applications that you have referred to. I think the secret is getting out, because they used to be $2, now they are $4. Still worth it.

There is a schematic on that link for using as a line out. They can also be used passively if there is a buffer in front of it (like a bypassed Boss pedal, or any opamp, FET or transistor stage). Without a buffer, a high impedance signal, like from a guitar, is connected across the transformer winding and is basically shorted out.

Good luck.