This is all simple stuff. I'm a simple guy ! It's prompted by a private
post from a US friend who only has 120v coming out of his wall. Most of
this will be obvious to daft old *******s like me, but newbies could learn
something from it.... I am an old newbie.... Does that count as an insult
??
Resistors, caps and most valves are cheap. Design your own, or use somebody
elses', schematic and valve audio only gets expensive when you get to the
big iron bits.
Output transformers are folklore.. RDH4 has a wonderful equation which
relates bandwidth/output power to weight !! Buy the biggest bugger you can
afford !! Good OPT's are heavy and expensive. You have to spend some
money ?? This is where you spend it !! An Ethiopian EL34 can be made to
sound great with the right output iron.
The power supply can be simplified and made relatively cheaply, however.
Your design could call for, say, a 300v-400v DC B+ at 200mA, 6.3vAC at 4A
and 5vAC at 2A
to run the heaters.. Combining it all into one transformer can make for an
expensive unit. Try splitting it up....... 1:1 ratio mains isolation
transformers are cheap. Using a voltage doubler rectifier could provide the
B+ you need, straight off an isolation transformer. Wire two identical 1:1
mains trannys with the primaries in parallel and the secondaries in series
and you get double the input voltage and also gives, with a bridge
rectifier, a centre tap between the two secondaries at 1/2 B+ DC which might
be useful.
6.3VAV ? Not a standard voltage, but 120v or 230v to 6V is, and Radio
Shack/etc do them dead cheap. Pick a 6V tranny with a current rating 50%
higher than you need and because it's not fully loaded, you will get the
right side of 6VAC out of it. 5VAC ? Nobody lists a 120 or 230 to 5V
transformer ? Fine, use a 6V one, and lose one volt through a series
resistor....
This is either useful or a load of crap.
Better than AJ though
kind regards to all
jim