Hey Jim,
Hope you're feeling better. Agreed that ASIO4ALL is pretty bad... I tried the AQVox demo driver, but it was not happy in my HP Z400 (dual W3505 Xeons, 8Gb DDR3 RAM). The best fall-back position for me was to go to WASAPI with Foobar 1.1.2 b3, since I'm running Windows 7 Enterprise x64. With WASAPI, there is no intermediate (OS level) driver, it's just Foobar plus the WASAPI output support dll installed in Foobar's component screen. Not sure if WASAPI allows hardware-level access to the USB transceiver - probably not, as there's an API in the way. But it sounds markedly better than Foobar thru ASIO4ALL!
By the way, I know that there is a lot of concern regarding Windows threading and streaming audio continuity/quality; I've recently rebuilt the HP under the guidance of a friend with MCSE credentials, and it's logging less than 130 microsecond DPC latency, with an absolute maximum of 162 microseconds. Sounds pretty good, but still not as good as the Musical Fidelity A308CD... but then, I have a USB-powered DAC from Pro-ject, and I know that the internal DAC in the A308 is better than that... I need to investigate a Valab NOS DAC from eBay to tide me over for a while... <g>
Jim, I haven't done a lot of reading on the Windows Audio Session API, but I'll do some checking and let you know more about how it works. Right now, I'm listening to the Crack on my HD-600s, fed directly from the A308CD. I'm actually pretty impressed, the more I listen. I've installed a NOS Sylvania 6AS7G, which I got for a song on eBay. Now, I realize how low the noise floor of the Crack can be - my stock 6080 had a very low level hum in the right channel.
Probably more importantly, I replaced the ElectroHarmonix 12AU7 with a Amperex Holland Bugle Boy, also NOS. That guy cost a bit more, but he's definitely more "elegant" than the EH, which had nearly 100 hours on it when replaced. On the recommendation of Mr. Lee Hankins, I bought a couple of 12BH7s on eBay for less than $15; they are in transit. I will advise when I get them swapped in and get a couple of hours on them...
This is so much fun, Jim. I'm thinking I need to build another Crack, with a Speedball, just to open up my tube rolling options. :-)
More to come on WASAPI when I clear this week's logjam at the work house.
Cheers,
Don