This one is really cool in that it uses a power transformer which can be bought at any well stocked electronics supply. It serves in a communication receiver quite well. If you are and audiophile you might want to pass this one up. I priced the transformer at Mouser for about $10.
NOTE: In the sims I am using a green LED. The bias is effected by the LED voltage which varies with the color.
EDIT: oops! DIT pointed out I used 2 transformers. She intends to use 1 with 2 primaries and 2 secondaries.