Fleetie wrote:
I am VERY interested in learning about how to design valve amps,
but before I do that, I want one for my hi-fi, that just works.
Then I'll worry about how to design them myself. I guess the
simplest design to start off with is a Single-Ended Triode
amp - would that be right? Only one grid to worry about, and
only one power valve. Might as well walk before one tries to
run!
But for now, I just want a working valve amp for my hi-fi.
Ok,
First up, Single ended anything is simple on paper. BUT. to actually
make it sound as you might wish, its not quite that simple. As SE is
simple everything is important. Its very dependent on the regulation of
the power supply, so either you have a complex regulated supply, or you
use choke regulation, which means big (as possible) chokes, Then the
last cap in the power supply is in parallel with the output transformer,
so you can't just use any old electrolytic and expect good results. Most
SE designes are limited in gain, so feedback is not used (avoiding that
flame war), so you need the most linear output device, which leads you
to directly heated triodes, then you have to consider the fillament
supply, DC hums less, but AC sounds better. Then its all down to the
transformer design. And so on, and thats even before you look at the
driver stage and the coupling methods.
Trust me for the moment, single ended is anything but simple....
So for a entry valve amp, go for a push pull, with a tad of feedback,
and in the price range you mention, you can either fall lucky with a
60's amp, that doesn't need a lot of work to restore (which ain't going
to happen), or you look at a kit, or something from the far east, or both.
So given that, I would suggest either
WAD kit
http://www.worldaudiodesign.com/wadproducts/kel84.html which is
a very good design, near or as good as their more expensive kits.
DiyHiFiSypply Kit
http://www.diyhifisupply.com/diyhs_ella.htm, which is
a very nice amp, but with duty and shipping may be above your range,
eBay far east
http://cgi.ebay.co.uk/ws/eBayISAPI.d...=5702396 582#
But I have no idea of what this is like, or how they are to deal with.
Though this is tempting considering effort it has cost me so far
assembling bits for a SE GM70 amp.
http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=5702697 607
--
Nick