Valve hi-fi amplifiers

Wizard

Since being completely converted by the difference between valve & ss for guitar amps, my interest will surely turn to the same for hi-fi.
I had seen these little amps advertised on gumtree:

http://www.trendsaudio.com/
http://capetown-westerncape.gumtree.co.za/c-Stuff-for-Sale-tv-audio-music-audio-music-equipment-Trends-Audio-Valve-Preamplifier-W0QQAdIdZ279884372
http://capetown-westerncape.gumtree.co.za/c-Stuff-for-Sale-tv-audio-music-tv-dvd-equipment-Trends-Audio-Digital-Intergrated-stereo-amplifier-W0QQAdIdZ279883647

I had assumed they were a gimic until I ran into an old friend at work today who is an uber-audiophile ... who has bought these Trends things and says the sound is deadly.
He has invited me around to go listen.

Very interesting.

Anyone have views on valves for hi-fi?

Gearhead

Two words: midrange transparancy. I believe the main reason for this is that most solid state amplifiers use large amounts of negative feedback throughout all amplification stages. This is necessary to get good linearity but also causes transient modulation distortion. The easiest way to understand this is when you realise that there is a time lapse between the signal going into a stage and it being fed back into the input of the stage. As long as the signal is the same, there is no problem; as soon as the signal changes, the negative feedback is causing the amp stage to add a mistake. All the mistakes put together cloud the music and make it more tiring to listen to.
None of this with well designed tube amps, that have no local negative feedback and maybe a few dB of global feedback, maybe none. Tubes are rather linear by themselves and whatever mistakes they make, sounds reasonable to our ears. If the designer of the amp compromised too much, you are not going to have thumping bass or slithering high end. Can be done, though.