Maximum volume levels go up, of course, with a headphone amp, allowing the connection of high impedance studio headphones as well as easy-to-drive earbuds and noise isolation designs. But as well as going loud, this amp delivers dynamics, and it delivers them by the JCB scoop-load. The opening to Mahler's 5th Symphony, for example, is a very difficult trick to pull off, requiring both subtlety and power, but the Voyager managed it without breaking sweat. The clarion call of the trumpet sounded clear and natural and the orchestral strike crashed in with and edge and power that I've never heard from an MP3 player on its own.
The bass from the Voyager is balanced and defined too, without being excessive, but even here if a fuller sound is your thing, or your headphones are a little lean, you can correct this by flicking the Contour switch on the side of the Voyager. Unlike equalizer settings on most MP3 players this boosts the bass without warping or degrading the sound quality.
I also own a home-brewed headphone amp based on the popular CMOY design, and while the Voyager can't match its sheer brute force and aggression it is far more forgiving and subtle, presenting the music in an unforced and ‘easier to listen to' manner, yet without ever veiling the details.
And it'll pull off its tricks no matter what source you connect it to. I tried the Voyager hooked up directly to the stereo outputs on my high-end rack-bound CD player - a Unison Research Unico CD - and it did just as good a job. This highly revealing source, which makes use of a hybrid transistor/valve design, can be painfully revealing and difficult to listen to when paired with the wrong kit. I can't connect my CMOY headphone amp, for example, and listen to it for longer than a few minutes at a time, but with the Voyager the music is phenomenally involving and enjoyable. Hooked up to a PC, a Squeezebox and my home made DAC proved the point further with excellent performance in each case.
There's no denying that the Voyager is an expensive piece of kit. It's not very practical or good looking either. And there are far more economic ways of beefing up your portable audio experience - if you're happy to go with the DIY approach, you can buy a decent amp on eBay (such as the CMOY-based amp mentioned above) for a fraction of the price.
But if you want the best, at least in the world of high-end audio, you have to be prepared to pay for it, and this is undeniably there or thereabouts. For this level of quality, £179 to me sounds like a pretty good deal.