Over the past few years, I've dabbled with a number of "digital" amps (they actually aren't digital, but that's a whole separate discussion) and have had positive experiences with some of them to consider them seriously for a permanent place in my hi-fi systems.
I remember my first experience, the first generation Sonic Impact amp based on a Tripath chip with 5W output. The gasp that came from the small group that had gathered at my house was not really related to the sound, but more the shock that the tiny little amp could drive my Monitor Audio bookshelf speakers, powered by 8 AA batteries no less !
Fast forward, and I've tried a number of technologies including Tripath, proprietory (Flying Mole), B&O Icepower and now Hypex.
The Hypex was purchased second hand through a local hi-fi forum and was assembled by local modder and DIY supplier, James from Effective Audio Mod.
Here are some photos including some a shot under the hood. As you can see, it is a dual mono design with separate transformers and power supply boards for each channel. There is a motorised Alps potentiometer in front with a toggle switch, so you can use it as an integrated amp or power amp.
Sound wise, the Hypex seems to stray from the path of the sonic balance of most "digital" amps in that it avoids having the subterranean bass that seems quite common for these powerhouses. In fact, the sound of Hypex reminds me very much of the sonic balance of Tripath based amps.
The bass is quite well rounded with a certain amount of fullness (reminds me a bit of my tube amps ... of course my tube amps have much less control in the bass region). Its midrange is quite neutral with this balance maintained up to the high frequencies.
Amongst all the "digital" amps I've owned or heard, this one has the most pleasing highs. It doesn't sound etched, or dry. There is a nice sparkle and the communication of acoustic space is excellent. When listening to Patricia Barber's excellent drummer, the way the high hats shimmer is absolutely sublime. In case you think I really like this amp .... I do !
The above is with the built in passive potentiometer (Alps blue velvet). Paired with a Diva M7 tube preamp, the midrange becomes slightly fuller with the high frequency maintaining their shimmer but losing a bit of separation in favour of a slightly more organic presentation.
I also found that the Hypex matched very well with my Thiel CS 1.6. It had just the right balance to warm up the bass while maintaining the Thiel's neutrality and speed in the midrange and treble. What if you can't afford the Hypex ? Think seriously about a Tripath amp if you can get away with its power limitations. I have a Kingrex T-10U that I'll write about soon.