Like everyone else reading this review, I purchased this item on the basis of all the incredible things I had heard about it. And while it is unquestionably a good amp, there are certainly limitations as to how much it can enhance listening pleasure or provide improvements to the sound.
My set up is as follows:
iPod Classic 30GB -> Belkin connector via dock -> GS Voyager - > Sennheiser 595 or PX100
I use a mixture of Apple lossless and various mp3s (192k minimum)
The Voyager takes a substantial amount of time to break in. I would say you need at least 160, maybe 200, hours on this thing before you start to hear the benefits. And when you do, they are quite subtle. The GSV eases the treble sharpness of the stock iPod and provides a general "meatiness" to the sound that wasn't there before. My favorite quality is the aggressive, growling midrange - great for old-school '70s Punk! It's a sound that's oozing character. On lusher music, it sounds pleasingly full and provides a transports-you-somewhere-else quality. Walking around the street with PX100s, you can easily obliterate what's going on around you. It really does feel like your not even there in the real world (I consider this a good thing).
On the other hand, and I'm not sure wether this is the iPod or the GSV, but the overall tone is hard and brittle. I find this feature on both Apple Lossless and 192k files (interestingly resolution doesn't seem to make an awful amount of difference generally on the GSV). I find this brittleness pretty unpleasant generally and much prefer to use the contour switch which gives it a huge bass boost that also softens the overall sound. Definitely more fun to listen to. Yet on the whole, the positive differences that the GSV provides are too subtle to justify its cost and this is further compounded by its treatment of poor quality sources. A poorly mastered recording will still sound poor maybe even more so on this equipment and while this may be the aim of Hi-Fi manufacturers, it doesn't exactly make for an engaging listen. Believe me, where mp3s are concerned you absolutely DON'T want a transparent amplifier. Another gripe is the lack of headroom on the amp. Push the volume past 12 o'clock and nasty distortion sets in. It's so nasty, you have to switch it off. As I alluded earlier, this could be the mediocrity of the iPod that's being revealed but until/unless I purchase another mp3 player, I cannot validate this for sure.
People interested in the GSV are generally those looking to improve the sound of their mp3 players. I do not think purchasing the GSV is necessarliy the best way to accomplish this. The primary objective should firstly be to obtain quality headphones, then a quality mp3 player. And then if someone's really obsessed with optimum sound then they can experiment with the GSV. But as it stands this is neither an essential upgrade nor an audiophile delight.
Mine's just sitting in the closet gathering dust.