[sdiy] Adding offset to vactrol??

[Dave Magnuson]

Hi Dan,

I don't really have an answer to your particular circuit needs, but thought 
I should mention this:

While you're playing with vactrols, try the H11F3 opto-FET.    It's not the 
same as a vactrol, but can be used in similar ways.       The H11F3 is quite 
fast.  The FET acts essentially like a voltage controlled resistor and can 
be used instead of a vactrol in some instances.

I typically drive the FET with a simple transistor circuit (the same type of 
driver you'd use for a panel-mounted LED indicator)

They're cheaper and more readily available than vactrols, too.

Dave


>> At 07:48 AM 6/3/2008, Dan Snazelle wrote:
>>
>>>I have been playing around with vactrols. VTLC53's and clm6000's. I
>>>would like to use them with CV sources. I would like to be able to
>>>add some offset of some kind so that i can get around 2 issues:
>>>
>>>1. they dont start reacting until a certain voltage ( is it 2
>>>volts?)-is there a way around this?
>>>
>>>2. they stop reacting when being driven by a high frequency from a
>>>vco or lfo. (not that high a frequency either. the led just STAYS
>>>on. for example is there a way to add an offset so that the vactrol
>>>thinks 1khz is actually 350 hz -this is just an example but i'd love
>>>to be able to actually have the vactrol send out a cv that can
>>>follow a vco from very low to very high.
>>>
>>>any help greatly appreciated!!
>>>
>>>thanks
>>