GGG DOD 440 Envelope Filter Question

[mutagenic]

Hi Folks,
I just built a General Guitar Gadgets DOD EF440 clone.  I'm not that familiar with envelope filters, so I'm not entirely sure if it's functioning properly.  I can dial in some nice auto-wah sounds in the mid-range of the "level" and "range" knobs, but when the "range" is adjusted to around 4 o'clock or greater, I get a sort of squashed distorted tone.  Am I supposed to have auto-wah sounds throughout the entire range, or is what I'm getting normal?
Thanks very much.

[Brian Marshall]

since the 440 uses the same IC for the filter, and envelope follower, what you are hearing is bleed through of the envelope follower amp clipping.  This could be aleviated if you used two sepparate opamps, rather than one dual opamp.

Anyways, this IS normal for this circuit.  It will vary a bit with different opamps.

[Pushtone]

I built one of the GGG 440s and it sounded great with excellent range on the pots.
I sold it to a buddy who had to have it. That was a mistake because the second one I built
sound distorted as described above. I used the exact same parts. Confusing?

I'll go back and try some different opamps in it if I have something to substitute for a TL022.
That first one sounded so good. I hope I can get it sounding right.

Thanks for the tip Brian.


Dave

[Mark Hammer]

since the 440 uses the same IC for the filter, and envelope follower, what you are hearing is bleed through of the envelope follower amp clipping.  This could be aleviated if you used two sepparate opamps, rather than one dual opamp.

Anyways, this IS normal for this circuit.  It will vary a bit with different opamps.

Nice to see you back here Brian.  Your absence is understandable, given how busy you've been.  The new Subdecay pedals look great.

[mutagenic]

since the 440 uses the same IC for the filter, and envelope follower, what you are hearing is bleed through of the envelope follower amp clipping.  This could be aleviated if you used two sepparate opamps, rather than one dual opamp.

Anyways, this IS normal for this circuit.  It will vary a bit with different opamps.

Thanks a lot Brian, very informative!

[Brian Marshall]

since the 440 uses the same IC for the filter, and envelope follower, what you are hearing is bleed through of the envelope follower amp clipping.  This could be aleviated if you used two sepparate opamps, rather than one dual opamp.

Anyways, this IS normal for this circuit.  It will vary a bit with different opamps.

Nice to see you back here Brian.  Your absence is understandable, given how busy you've been.  The new Subdecay pedals look great.

Hey Mark, 
Nice to see that you are still here.  I pop in from time to time.. Usually late at night, and see if interesting is going on.  I haven't gotten to build much stuff for my self in a long while.  I'm hoping to pass off some responsibilities to other people soon, and would really like to claim some free time again... or maybe even join a band again.

[fuzzo]

Hi,

I finsihed my DOD 440 clone, the filter can be heard, but there's a kind of really strange distortion with the filter sound. I think there're any mistakes, all seems to be good (I keep the values of GGG). But I used a TL072 instead of TL022.

I'll try with a JRC 022 but maybe you've some ideas about this problem ?