T-61 preamp/dac issue...

i had been using my t-61 pre for a while with an old beresford dac, but wanted to update the dac to something more modern. i tried the lovely sounding usb 2.0 emerald physics dac 2, but after three consecutive units (would constantly develop a 'telemetry' noise, beginning in the right channel, and eventually including the left), i gave up, as going back to the coax input on the beresford the issue vanished. still wanting to upgrade after discovering the emerald physics units sonic enhancements to my system,. i ordered an arcam rdac. after warming up the system, tested the dac by increasing the pre volume without any audio signal, and the 'telemetry noise' is back. even tried it just using the coax input like with the beresford, but still the noise persists. i have several sets of new and old tubs rolled them all. no difference. i'm waiting on a reply from audio mirror re issues with other gear when attached to the t-61. beresford dac works great, the two newer\different dacs have issues. any insights would be more than welcome.
ok, this is not good: looks like either all my sets of -ev/mil spec tubes are bad, or the pre does not like them. after powering down/disconnecting everything, switching stock 6n1p for the -ev, no issue. arcam seems intact, though now in win8 control panel/sound, when i test the 24/96 setting (default), it stutters on both channels...not sure what's up with that, but setting to 24/44 in sound devices fixes it (the test tones). the 24/96 setting has no issue during playback, but i don't have any high res files to test atm. i feel lucky i didn't blow up anything else. mark over at emerald physics told me an errant tube could have done much worse. even so, he's sending me a replacement dac 2. a total gentleman. thank you mark!