The one's on the input to the UCD, not the ones on the output of the crack ;-) That would have been exciting - 117V DC into UCD line level input.
The reason my UCD wasn't happy with the crack was because the lighting film caps (2x50uF in parallel each channel) I had used for output coupling had 0.5Mohm bleeder resistors in parallel with the cap. With two in parallel I had made a voltage divider with 250Kohm in the caps and 2.5Kohm (in parallel with the headphone or amp input impedance) to ground. With no headphone or amp attached, I had about 1V DC offset on each output. No wonder the UCD kept going into protection.
I risked damaging both my amp and HD800s. Fortunately the worst I have to deal with is a couple of Lundahl transformers at my mini aleph input that should be demagnetized (easy).
Needless to say if I'd used the parts Doc supplied and measured all voltages and resitances religiously as he rightly recommends, this wouldn't have happened.