I am quite excited by the arrival of a new, relatively inexpensive upgrade: an AQVOX 'low noise USB power supply'
This is a unit that powers the USB bus, and devices attached to it such as a USB DAC or the Audiophilleo, and takes over the duty of providing 5 Volts of power to that device in a regulated manner, where the laptop or PC you are using would otherwise have to provide that power.
The theory is: clean, robust power that isn't contaminated by whatever grunge the source computer is spewing out.
I was expecting the effect of this device to be subtle at best, but was unprepared at how it lifted the performance of the system overall. Vocals gained solidity, guitars more bite and more timbre.
It provides a pass-through USB type B plug – you plug it into the back of the Audiophilleo, and plug your USB cable into the back of that adapter, and then just plug it into the mains. Another mains socket consumed by yet another transformer, but hey ho: it works.
I suspect the laptop I'm using, an older generation Core Duo Macbook, isn't providing full power down the USB bus; I know that unpowered hard drives (the kind designed for use with laptops and which are entirely powered off of the USB bus) fail to mount, so it's no surprise that the Audiophilleo has been under performing. I'm now hearing what it can do, and the difference between it and the humble Toslink cable is clear; the latter sounds hard and flat and lacking in detail and timbre in comparison.