AW: AW: CA3046 exponential converter

[Haible Juergen]

	>That means that none are using 3 TR's for expo, 1 TR for heater,
and 1
	>TR as sensor TR?
	>As i have done in the tripple expo conv shemo at:
> http://home8.swipnet.se/~w-88660/schpcb.htm
> 
	>Does any one have any coments on the design please?

Looks pretty straight forward. I can't tell how stable the
temp regulation is - you'll have to build it to find out.

I was puzzled because I was looking for the "reference"
transistor (which would make an expo pair with each
of the 3 expo transistors) in vain. So you just use a single
transistor for each expo converter, and rely on the constant
temperature completely. I have seen this once, probably in 
the EML synths (from memory), using two halves of a 726
for two expo converters. I can't tell how well this works
(what's the general experience with the stability of EML
stuff ?), but most manufacturers didn't trust the temp regulation
to the extreme, and used the 1st order compensation of a 
transistor pair nevertheless.
I can see some reason to use a 726 economically, but there's
no real reason to go without a reference transistor in *your*
circuit. You could build a triple expo converter from 4 transistors
(like I did a quad from 5 in the 2040 style VCF), and still use
the 4th transistor as temperature sensor.
As I said; i can't tell how good the performance of your circuit
is, but I wanted to say that there might be a way to improove it
without much additional effort.

JH.