you can also get something similar to the rat shack models from parts express for $10. part number 265-012 :
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=265-012
the parts express version has the advantage that there might be other things worth buying from them, such as film caps, tube sockets, etc. if you need a cell phone, however, journey to your local shack.
when you open the parts express cylinder up, you see a pcb with these two transformers on it:
i used these on a build of PRRs compressor and they work just fine. i don't know if they are identical to the rat shack ones or not, but i bet they are similar.
with a 50ohm source impedance, i measured that +7dbu @ 20Hz = 1% THD. so they saturate, but they're not big, so no suprise there. very lightly loaded, they do ring a bit above the audio band, but terminated with 5k they are flat within 1db from 10Hz to 45kHz, -3db at 55kHz. i'm guessing that this is all due to the rather high interwinding capacitance (550pf) and that they look to be simply layer wound, one winding measuring 170ohms DCR and the other 220ohms. i measured a bit above 6H on the sencore, which is comparable to the edcor WSM600/600s. the edcors, however, have a much lower DCR, bigger core (harder to saturate), center tapped windings, and flatter frequency response.
so, have no fear, the ground loop isolator type transformers are fine. i bet the edcors would work just as well if not "better" though some may like the sound of saturation.
ed
