I like the DBM because I make the transformers and basically feel like it is a home brew. Take a look at the circuit.
2 cores 4 diodes and a little wire. What are the disadvantages? It require an oscillator to drive it and it produces a signal lose.
The B and E manual is available online so I guess it is not a problem that I linked it here.
David White B and E
*added the VEK-131k link.(the first one misfired?)