optical limiter problem

[Paul Perry]

At 03:37 PM 4/02/98 +0100, Juergen.Haible wrote:
>A few weeks ago I tried to build a stereo optoelectronic limiter, using
>a Vactrol 5C4/2, and I ran into a problem I did not expect.

>Because of the very nonlinear R / I characteristic of a vactrol, I have
>to use a feedback
>rather than a forward compressor topology. So I have a feedback loop,
.......problems......
>Any ideas ?

....well you might do away with the feedback loop by using that system
I last saw in Elektor 6 months ago, where you have two hopefully similar
quasi linear optocouplers.... one is forced by feedback to give a linear
response, and the other carries the signal. so you hope the nonlinearities
cancel out, which for your purposes I think they will.
this is a horrible description, but it WAS in Elektor under a heading like
'linear optocoupler'

paul perry melbourne australia

perhaps for your next party trick you could build a lfo from a thermistor..
they say it can be done!