UA726 replacement

[Chris Crosskey]

re: UA726
If you leave off the components that power up the heater completely 
and wire in an LM394 instead it should apparently work. I haven't tried it yet
but I will soon as I have a half-built Elektor Formant VCO in my box 
somewhere. I'll let you know how it goes. The reason it don't need the 
heater is because he LM394 is as close to two identical thermally 
bonded transistors as it  is possible to have, so although they drift,
they drift together, and so the circuit stays in tune if one is 
compensating the other. The UA726 used a different technique, by heating 
the tranny pair you could stop them changing  temperature at all, so 
they could be set up to compensate despite the fact that they weren't
very highly matched (though they aint that bad) That's the theory 
anyway, I'll have to try it out first. It's possible the MAT-02 will do 
as well, but I ain't got one of those, whereas I do have UA726's and 
LM394's so I can do them back to back. I gotta spare UA726 too if anyone
really, really wants one, I'm afraid I'll want 50 UKP for it, and 
posting it will be another 5 UKP as I will have to register it. Just had 
a look in my <Rare Semi's> box, I got two spares same price but if 
you have both only one set of postage. Sorry it's so fierce, but that's 
capitalism for you <g>. Willing to negociate swaps for CEM ADSR chips.
chrisc