This post - http://theartofsound.net/forum/showp...66&postcount=9 - referring to a Hlly T-amp 90 got me interested. I'd never heard of class T amps before, so I looked them up - http://en.wikipedia.org/wiki/Class_T_amplifier Seems they're a modification of class-D amps, and typically based around a chip - such as a TA2020.
Then I looked up some reviews, and I found this which refers to several DIY amps - http://www.tnt-audio.com/ampli/tripath_amps_e.html
One amp, the Sonic Impact (model 5066) seemed very cheap, and also quite elegant. However, so far I've not tracked those down. The reviews were a bit curious, as it sounds as though these class T amps have both a wow factor, but are also maybe a bit tiring to listen to. It's not clear how tiring, and how long it is before fatigue sets in. If it's an hour or so, then using these effectively with an alarm radio or similar perhaps doesn't matter, Maybe also the fatigue is less obvious if one is working at the same time - though it might depend on the work.
Looking at the review, mention is also made of Gainclones, so I looked them up too - http://diyaudioprojects.com/Chip/LM3.../LM3886_CA.htm Basically they seem to be amps made using only a very few components - typically ICs. Maybe quite good, and fun for DIYers and projects.
This article - http://www.6moons.com/audioreviews/sonicimpact/t.html - which is specifically about a Sonic Impact amp, maybe indicates some of the fatigue problems - with THD and noise rising as the power rises - see graph.
There's a thread on avforums also which is of interest - http://www.avforums.com/forums/hi-fi...jaw-drops.html
So, now my appetite is slightly whetted. I went to ebay to see what I could find, and these turned up - http://cgi.ebay.co.uk/TA2024-Class-T...item2a05c8622d For £20, if they work then maybe they could be a good buy. There are plenty of others, but these were the cheapest new ones I found. There are some SH ones from around £10, though usually shipping is extra. This one is similar, though probably uses a slightly different chip (TA2020 instead of TA2024) - http://cgi.ebay.co.uk/SA-36-Class-T-...item414e459e3f. You can see more if you search for "class T-amp" on eBay. I think some are probably intended for cars, but there's a lot of evidence that they can drive "real" speakers.
So, are any of these any good? Maybe they are "good value for money", but really sound "****", or maybe they're actually bearable. What do others think? I note that some people have tried making these or modding the amps - could be fun, though the results don't seem to be much better. At these low prices though, could be entertaining.