Poison Apple Auto-Wah Decay Time

moosapotamus

moosapotamus

Member
I just built the Poison Apple Auto-Wah. Everything is working and sounding great, except for the Decay control. For some reason I don't seem to be getting any action from it. Decay sounds the same fully CCW as it does fully CW. Is the Decay control just really mellow? Or, might I have mixed something up? Anyone have similar experience or know of a mod/fix for the Decay control in the Poison Apple Auto-Wah? Thx!
 
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I have found a couple of other schemes/projects for the Snow White (Poison Apple) Auto-Wah that show 47R for R24, instead of 4k7. So I replaced it in my build and now I can hear a little bit of difference in the Decay going from CCW to CW. But it is quite subtle. I would still be interested to hear if/how anyone else was able to get more action out of the Decay control. Thx!
 
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Based on the schematic, decreasing R24 will shift the range of the Decay control down. This will probably be noticeable at low settings and not that noticeable at high settings. You could jumper the resistor and slowly turn up the Decay control until you got the shortest decay you'd want. Then, if you measure between lugs 2 and 3 of the Decay potentiometer, this would tell you the ideal value of R24 for you.
 
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Also, make sure you used a C1M for the decay. If I recall, the first version of the board has the decay marked as B100k

If you're wanting longer decay times, feel free to increase the value of C8
 
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Thanks! With the jumper, I still can't get quicker decay. There is no decay at full CCW but at around 5 degrees it jumps to what is still a relatively long decay that increases a little bit at full CW. If this is as good as it gets, I'll just go with that. Can R24 safely be replaced with just a jumper, or should it be some minimal value? Either way, the Decay control doesn't seem very useful to me. Would there maybe be a better way to it?

Yes, I do have a C1M for the Decay pot. Full disclosure; I also changed R7 from 6k8 to 1k for more resonance and I changed R23 from 330R to 100R to try and make the response a little quicker, snappier. Not a huge difference but enough in the right direction to keep it that way.

Now I am also realizing that there is a significant volume drop. Are there any tweaks to the circuit that would increase the output, or would tacking something like an LPB-1 booster to the end be better? Thx!
 
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R24 works in conjunction with C8, so you might play with that value as well. The larger the capacitance, the longer it will take to discharge and visa versa.

If I'm reading the schematic correctly, you may be able to resolve the volume and the decay issue by adjusting the bias. I can't speak to where it's best to set it. You'll probably have to do it by ear.

If that doesn't work, R14 and R15 form a voltage divider. Increasing R15 should increase the output volume.
 
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Had a go at it this morning. For starters, I tried increasing R15 (4k7) up to 1M8 to try to get the output volume to match the bypass volume. But no luck. I'm back to the idea of just tacking an LPB-1 on to the output. Won't be the first time I've done that.

Adjusting the bias (VREF) for the entire circuit from the power section, to try to get some action out of the Decay control, seemed to shift the filter response up and down very much like what the existing Bias control does. But it does not seem to impact the Decay time.

I am wondering if adjusting the bias only for the sidechain (IC2.2, IC2.1, IC3.1), and not for the filter (LM13700), would be worth trying. Or, are there any other ideas about how to get the Decay control to do something?
 
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