I have the WA2, and before it was even delivered I got the Tung-Sol 5998s. Love them paired with my Grado PS500s.
You have to burn them in. If you're having a hard time finding these tubes, I bought mine from www.VacuumTubes.com and my hard to find Thomson 6111 I got from www.tubezone.net (for my Contintental V2...)
Then I got Woo's DAC a month later and talk about a day and night difference! Two songs I know well I streamed on Spotify Hi Res (Van Halen; "Take Your Whiskey Home" and "Could This Be Magic") made the music jump like David Lee Roth was singing right next to me with Eddie playing the acroustic guitar at my office. Jaw dropping. Money well spent.
I'm still burning in the Woo Audio WDS-1 but out of the box with cheap Monster cables I borrowed just to hear it, it sounded incredible. (Note: I recently updated to Cardas Clear USB and that was another meaningful incremental improvement.
For what it matters, i met Jack Woo at T.H.E. Show in Vegas (CES 2013) and he's such a nice, humble guy. So polite. So nice I almost bought the WA7 for "home" use as that sounded really incredible with his test pair of HD-800s (which are notoriously piggy on power). We'll see...
At first i was really confused with the WA2. Out of the box, I was sort of dissapointed. I didn't use a DAC. I wanted more. But then I learned that I wasn't using my correct headphones. My HiFiMan HE-500s weren't a good pairing per Jack.
Being a newbie, I didn't know this, and make no mistake, I am very happy with my Desktop Setup.
Edited by SMBuscemi - 1/20/13 at 9:12pm