[sdiy] Electric Druid VCADSR filter hysteresis

[Jack Jackson]

Hi guys,

Thanks for all your responses. You were right in the end. It was a case of accidentally connecting the opamp -ve to ground. The opamp I'm using is a TL072. 

It's working nicely now except I'm using a microswitch for the gate/trigger and the edges of the pulse sometime's arent sharp enough for the PIC to detect properly.


Best Regards,
Jack

----------------------------------------
> From: Alan.Needham at centrica.com
> To: jackdamery at hotmail.co.uk
> Subject: RE: [sdiy] Electric Druid VCADSR filter hysteresis
> Date: Tue, 2 Sep 2014 10:21:41 +0000
>
> You say ' except the opamps of the low pass filter lock at +15V' - both stages, so there must be a problem on the first filter stage.
> Are the op amps powered with +ve and -ve rails, not +ve and 0v? - thinking some sort of phase inversion thing.
> Could there be something weird with C4 - very 'clutching at straws' that one though!
>
>
>
> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Jack Jackson
> Sent: 01 September 2014 22:10
> To: synth-diy at dropmix.xs4all.nl
> Subject: [sdiy] Electric Druid VCADSR filter hysteresis
>
> Tonight I've built Electric Druid's VCADSR circuit and it seems to be working fine except the opamps of the low pass filter lock at +15V when there is no input (or almost no input) from the PIC. This means they always have to 'jump' down to 0-5V when the ADSR is in use.
>
> I've double checked my breadboard of the circuit and I can't see any errors. Any idea what I could have done wrong?
>
> Best Regards,
> Jack
> Like
>
>
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