I'm presently demo'ing an EE Dac thanks to the generosity of
Bill@LakeGeorge. I've also got Mullard and a couple Siemens tubes to roll. I am using the EE as a Dac with an Empirical Off Ramp 3 w/Ultraclock & Paul Hynes SR3-12 power supply and a Locus design Nucleus USB cable.
Now I've been doing comparisons between the Off-Ramp 3 and the EE USB Dac,,,, gotta say that it's mighty damn close comparisons here. If this Dac had been around a year sooner, I could have saved over $2G on a needless transport. The EE USB Dac is that good.
But my 1st day wasn't so positive. My system is highly dynamic with solid 3D imaging sound stage. These are all highpoints of the EE Dac and I found it a little overwhelming. In comparing this Dac with a TDAC while at Bill's, I found out that the gain on the EE dac is significantly higher (volume knob at full). While this wasn't an issue in Bill's Salk HT-3 system, it was with mine. But simply turning down the volume on the EE Dac cured that issue for my system. 5:00 being the max volume, simply going to 3:00 tempered the dynamic issue for my system and while it's still a bit too much of a good thing for me personally, if I hadn't found the Havana Dac which just works better for what my system needs, I'd be all over this Dac. It does so many things good that I could easily live with this Dac and be both happy and a little more richer from the money UI would have saved. In Bill's Salk system, the EE Dac w/Mullard ECC82 tube provides an incredible 3D sound stage depth with nice tight bass. We both agreed that the EE Dac was the preferred Dac over the TAD TDAC or the AVA insight+ Dac.

(I will be bringing my Havana w/Bendix Red Bank 6385 tube over to Bill's in the near future after it's had it's cold bath)
During my demo, I have been using a Herbies Ultrasonic RX-9 ring on the tube (it's for my Havana tube) and I found a positive clarity improvement with it's use. I would highly recommend an EE owner try this tubetweak out with Herbies 90 day money back trial. Trust me, it's cheaper shipping than a CD.
As tubes go, I really like the Mullard ECC82 for it's 3D sound stage presentation but the Siemen tube has a higher clarity but with a punchier bass. I had to turn down the Bass 2db but it could be that this NOS tube simply needs some miles on it. I've only been using it 1 day now and I'm loving the clarity gain with it. I think I still prefer the Mullard ECC82,,, still too early to be sure. I like I love tubes.
I need to agree with Levi, the Eastern Electric USB Dac is a true giant killer,
especially in a PC audio system.
Cheers,
Robin