any words of wisdom for usb noise problems?

Yep -saving up for the next great thing... Steve and Gordon both have some nice things to consider =)

For Wkraft - please forgive me if you know this....

The Waveterminal is just a device for converting USB to SPDIF/Toslink. Actually it has a DAC built in too, but I have never seen anyone comment about using one. It was developed and marketed to the semi-pro audio recording market

As a general point of info, USB devices come in two flavors - those that require a dedicated power supply (because they need more juice), and those that can draw their power from the USB cable. In fact the Opticis needs a power supply and what Steve has done is create a DC one instead of the AC wall wart. The U24 is an example of a device that does not need its own power source. But effectively that leaves it connected to the computer...

I would assume that any USB DAC (certainly all that I am aware of besides the Waveterminal) require a dedicated power source, though some (like the RedWine units) are battery powered since the DACs tend to operate at 5v.

to elaborate- the waveterminal running into the coax digital input of my panasonic sa-xr55 (i know many will turn up their noses at this class d based unit) results in dead quiet speaker and headphone output. this prompts me to wonder what in the receiver prevents the noise transmission. i see that most audiophiles are not using the u24 dac function, and i am thinking ahead- would implementing certain kinds of dac obviate the need to uncouple the u24 from the dac.

I have used the Waveterminal for almost two years now. It a a great device but I am sure one f its short comings is that it draws its power from the PC via the USB cable. I have spent a lot of time listening to it as a DAC and it is phenomenally good sounding given its price. I am awaiting one of Empirical Audio's new wirless USB offramps. You can find info at their site.

This is clearly a design fault of the U24. They should have put a circuit inside to clean the power via usb and/or add the possibility to connect the U24 to an dedicated external power supply.

I tried an external USB-hub with it's own external power supply. Unfortunately the U24 isn't recognized by the computer when connected via the hub but maybe this is just a matter of reinstalling the U24 drivers.

I am thinking now of modificating the U24 to make it work with an external power supply. The easiest way is probably to cut the USB cable in two and connect pins 1 and 4 of the part which leads to the U24 to an external power supply.

Not a design fault - more likely a design decision, and by modern standards by now an old design. The U24 was built as a semi-pro recording studio product, not as an audiophile product. Recording studios are filled with all sorts of devices using less then optimum electronics.

BTW the hub may not be able to power it.

Using the Opticis fiber optic USB may give you that last degree of quiet you are looking for.