George: thanks for all the insight. I can't seem to find the burston 100 anywhere --- would a musical fidelity x-dac tube buffer work also? There's one in the classifieds now: http://app.audiogon.com/listings/musical-fidelity-x-dac-v-3-tube-stage-buffer
Or are there other tube buffers you consider reasonable for not messing about with the signal?
Or are there other tube buffers you consider reasonable for not messing about with the signal?