[sdiy] help with clicks on VCA

[Tim Parkhurst]

Hey Dano,

A couple of thoughts. First off, what kind of audio are you running
into the tremolo? If it's something with a DC offset (guitar, some
recordings, maybe a battery powered gizmo), you might want to think
about AC coupling the audio input with a cap. Say, a 0.22uF polyester
or mylar film. Secondly, you might need to bias your CV so that it
doesn't go below 0V. Of course, it doesn't make sense to have a CV
below 0 on a VCA (assuming that 0V equals full attenuation and 10V
equals no attenuation), so if you're using a typical +/-5V LFO signal
as the CV source, you might want to try biasing it so that it ranges
from 0 to 10V instead. I don't know if this would be the source of the
clicks (probably not), but it would result in 'non-tremolo like'
behavior when the audio would be completely off for the negative half
of the waveform.

Tim (completely off) Servo
-- 
"Sire, the church of God is an anvil that has worn out many hammers."
- H.L. Hastings


On Sun, Aug 16, 2009 at 1:03 PM, Dan Snazelle<subjectivity at hotmail.com> wrote:
>
>
> I am trying to make a tremolo.
>
> I have tried with an OTA vca and with an SA571 vca
>
> the SA is better as I dont have to worry as much about the peak to peak values coming in and the CV rejection is better
>
> BUT
>
> neither are ideal
>
> when driving with a squre or TRI wave i get all kinds of CLICKS imposed on the audio (i am not talking about
> when there is no audio coming in. i am talking about clicks imposed ON the audio)
>
>
> anybody have any ideas on how to remove these clicks?
>
> someone recommended slewing the Control waveform.
>
> i was quite surprised that an OTA was so prone to this
>
>
> thanks
> --------------------------------------------