At the heart of the rPAC is a TI Burr-Brown PCM5102 DAC chipset, the same one used to such good effect in the drDock. Arcam throws out numerous stats which certainly look good on paper (see below), but the highlights are the support for 24bit depth, sample rates up to 96kHz, a frequency response of 10Hz to 20kHz and headphone output power up to 138mW - enough to power the vast majority of headphones without issue.
On top of this is RF suppression which combats the interference created by high frequency radio bands inside a computer from the likes of the power cables, ports and the internal microphone. The cherry on the top is the inclusion of asynchronous USB which reduces the noise and jitter associated with USB music sources. This problem occurs due to the computer being responsible for the timing in the playback. Asynchronous technology bypasses that by using its own precision clock circuits to control the timing inside the DAC.
Upgrading from a typical onboard sound card to the rPAC results in immediately obvious improvement across the board. Like the drDock, the rPAC brings greater clarity, depth and deeper, more resonant bass. Moreover, the general background hiss and audiological grime that poor quality computer audio is covered in is essentially eliminated. A crude analogy would like listening to music from behind a closed window then opening it.
If we can level a criticism it is that the treble does occasionally sound a little shrill, but we found this only on tracks with particularly wild sonic make-ups such as A Lily's 'Lights Shone Brighter, My Delicate Sun Is My Sparklin' Sun' which is hardly representative of the vast majority of music!
It should also be noted that the rPAC isn't only at home with music. Any audio emanating from your computer will be given the once over, so it will enhance everything from streaming video services like Sky Go, and BBC iPlayer particularly when watching good quality content like films on the former and nature documentaries on the latter (not to mention Later With Jools Holland). Internet Radio also receives a welcome and much needed boost whether it is music focused or simply conversation based like BBC Radio 5 Live. In short we found no situation where our computer's audio output did not enjoy substantial benefit.