[Anders]

I think the 717 is a very good amp, especially at used price. It is a neutral amp without any harshness or other treble artifacts . It has a very slight warmth but does not add any artificial warmth (with my Reimyo DAC). It will reveal source weakness but that must not necessarily sound bad if there is some synergy!

My main complaint with the 717 is that it has somewhat limited output power and does not drive the O2 to its full potential. It drives HE60 and the 404's much better than the 007t amp and I think the 717 has fully adequate driving power for these headphones. But I still think that the 717 is very good with O2's but it is a little lacking in bass that is not hitting hard enough and too soft and uncontrolled. That also makes the overall presentation lacking some impact.

I don't like the O2 with 007t although it works more or less well depending on type of music (hint: bass content). I think that 007t with Electro-Harmonix tubes sounded better with O2 than with 404 and HE60. The tube brightness was not so apparent with O2 as with the other headphones but I finally swithched back to Raytheon because the EH are too bright with the lesser headphones and to the extent I will use the 007t it will be with HE60 and Lambda type headphones. The somewhat eyuphonic character of the Raytheons can also be a nice complement to the much more netral 717.

Both 007t and 717 sound better with the balanced input. I don't know if it depends on the amplifier design or that the balanced output on the DAC is better (my unbalanced cables should be at least as good as my balanced).

The new Woo offering is interesting indeeed. The same output tubes as the Blue Hawaii should give it adequate driving power. Headamp electrostatic amps are currently unavailable (at least for most of us) and I hope Woo will make a really good amplifier. But the 717 should definitely be the best value for money.