[sdiy] Adding offset to vactrol??

[Tom Wiltshire]

Dan,

On 3 Jun 2008, at 15:26, Dan Snazelle wrote:

>
> because i cant get a good control voltage!
>
> here is the scenario. i wanted to try and get a 4024's signal to  
> create a CV.
> sadly it tried converting this great square wave to a cv using an  
> lm2917 but it doesnt track very well.

You're trying to get the pitch of the 4024 square output turned into  
a pitch CV, right?

If you've tried this with a LM2917 and found it wanting, I'm afraid  
you're unlikely to do better with anything based on a vactrol. There  
may be other chips available that would do a better job for audio  
than LM2917, but I'm afraid I don't know of any. Perhaps someone else  
has more experience with Freq-to-voltage ICs?

Frequency-to-voltage conversion is possible, but has its limitations  
since you need to see a few pulses before you can possibly know  
accurately what the pitch is. Thus there is always a certain time  
lag, particularly if you're trying to convert low frequencies.

Regards,
Tom