Power supplies are the most important part of any audio system and this is what sets apart really live sounding systems. The source is also extremely important. The USB data should have no errors and low jitter. A fast-reacting, low-noise supply is required. Most linear supplies don't meet this criteria, with one exception, the Power Block from Empirical Audio. It is also a common-mode filter.
The Power Block uses a toroidal transformer which provides up to 5 amps at 5V. It is extremely low noise and very fast reacting, utilizing a Hynes-type voltage regulator. Hynes regulators beat all other regulators due to their unique topology. The Power Block was primarily designed to be used with the Empirical XMOS USB interface that is in prototype stage right now, but can be used with any USB interface. XMOS interfaces improve significantly. It runs on 117VAC or 230VAC. Here are photos and more info:
http://www.audiocircle.com/index.php?topic=128620.0
The Power Block is $799.00 plus shipping and PayPal fee. 30-day unconditional money-back, less shipping. Use "Contact us" on the website we will get the order shipped. They are in stock.
Steve N.
Empirical Audio