"Frank Stearns" wrote in message
...
I need to cobble together a single-channel two-way mic splitter -- one
output "flow through" and the other transformer isolated.

I've got an ancient Triad line-to-line audio transformer: each side has
600 ohms with taps for 250 and 50 ohms. (Model number is rubbed off, but
it's a metal can, 3/8" stud mount, roughly the size of a shot glass with
leads coming out through the stud,)

This old beast actually looks pretty good on the 'scope; respectable
square wave performance once I put a 220 ohm resistor across the output
(otherwise rang like a church bell).

That could be a problem, as many modern mics prefer to see a higher
impedance, like 1.5k. Still, try it and see.

The flow-through is for recording; the iso-out is for PA.

A few questions to The Wisdom:

1. I figured on using the 250 ohm taps on both sides. For the transformer
output side, should I continue with that 220 ohm resister across the
output? (I assume "yes" given most modern preamps.)

I'd try the 600 ohm taps on both sides. You may be able to use a higher
termination resistor, which at least some of your mics may like. Oh, and
don't forget the recording preamp will be in parallel with the loading
resistor, so it should be higher (parallel resistances add using the formula
1/total = 1/R1 + 1/R2).

2. On the input side to the transformer, should I "bridge" the
flow-through mic line with some resistive value, or just make a hard-wired
"Y"? (The flow-through line will be carrying phantom power.)

Try just a Y.

3. I'm assuming I should float the 50 ohm legs on both sides of the
transformer... or should I terminate them in some way?

Float.

Peace,
Paul