The Shop > Electronics & IC Programing
6A PSU using L200
Bluechip:
John
Never had much to do with discrete transistor audio amps. Built several valve Mullard 5-20's / 5-10's, but the only one I ever built was a ( Williamson ? ) pair from a kit bought by a character in the pub who then decided it was a bit beyond him ... seem to remember MJ340 or similar. Worked OK for him anyway .. got some free beer. He was happy, I was happy... briefly IIRC...
I don't see why the comp. pair arrangment shouldn't work .. must admit I just modify stuff from the .pdf's. There is a cct. using a 2N3055 as a pass transistor, don't know if you've downloaded the things .. but it's more involved than the pnp jobby I did. I just paralleled ( ? spellcheck ) .. the two off with the usual emitter ballast resistors to even 'em up a bit. Not needed if you have a lot of transistors to choose from, and the patience to find a matched pair.. Can't be bothered, just ballast the damn things. QED.
I have used the uA 723, long time ago. At one time it was the device of choice, seem to remember them in a metal can .. might even still have some..
First used the L200 in 1978, a mate worked at a semiconductor/ electronics bits wholesaler. Managed to scrounge a 'developers sample pack of 10 ', never used any other adjustable reg. since then. Bit inconvenient having to pay for them. Never forgiven him for resigning to go somewhere else better paid. No thought for others, some people ..
Dave BC
John Swift:
Hi Dave ,
I can see why you use the L200 regulator , it is nice and simple and the price is right :)
variable power supplies I have built in the past could go down to 0 volts and one had variable current limiting as well
with the L200 chip you need a negative 3v supply to do that
a charge pump circuit could generate that from the positive supply or use a transformer with a centre tap ?
BTW the wiliamson amplifier was a valve amplifier , I should have the circuit
have found on the 'net the circuit of a John Linsley Hood design that may be similar to your amplifier
John
Bluechip:
Hi John
Just looked up the Williamson amp. Too true, it is a valve amp. So why did I think the one I did was one ?? Another bit of brain shot :scratch:
That J. L-H looks familiar, but the output transistors don't match my memory, vaguely remember MJ340 for some reason ??
It was only a pair of P.A.'s I built for him, 'cos he connected them to a posh ( Nordemende ?? ) walnut veneer radio-gram. Which had the pre-amps/equalisation stuff in it ...
I don't think there's much that can't be done by torturing a '555. .... :lol:
Dave BC
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