# Cataclysm / PT2399 delay w/drive control...



## LukeFoxes (Jan 1, 2022)

Hi all and happy new year!

I've been stewing on this for a while, wondering if anyone might have some idea on mods that might allow for a gain / drive control for PT2399 delays? Thinking of messing with my Cataclysm PCB to see where I can take it. Maybe some really dirty repeats or just dirt overall.

I'm not sure if working with the gain / feedback network on the input buffer would be best, or messing with the 1st LPF stage of the PT2399?

The ideal would be something similar to what Caroline have in their Megabyte / Kilobyte pedals, if anyone has any suggestions on where to start I'd love to know!


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## mdc (Jan 1, 2022)

Look up the 'sewer pipe ringverb' and the pt2399 'noise ensemble' for some ideas - they're both very cool, blown out implementations of PT2399 reverbs.


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## LukeFoxes (Jan 1, 2022)

Thanks @mdc!

I did do a bit of reading on these but found they're more of a noise effect, rather than a pre-amp style overdrive. What I'm after seems simple enough in theory but I'm struggling to get my head around how to implement it. I've messed with the pre-amp stage of the Cataclysm a bit, including diodes in the feedback loop and messing with the gain but it's not working how I'd like.

Anyone else have some ideas? I'd love to hear back!


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## mdc (Jan 2, 2022)

Are you looking to have distortion ONLY on the delay line?

If so, looking at the schematic, the output of the PT2399 comes from pin 14 on the chip. You could pull C23 out of the PCB and build a small distortion circuit like a bazz fuss or an electra or similar single-transistor thing on stripboard and use the + and - pads as jumper points. 

That would give you control over distortion on the repeats, but leave the delay line tone control as-is. It wouldn't affect the clean signal at all.

If you want distortion over the whole shebang, personally I'd just build any ol' OD/dist/fuzz circuit that I liked, put the two things in a box w an order switcher and decide whether I liked distorted delay or delayed distortion better.


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## mdc (Jan 2, 2022)

You could also put a pair of buffers and some switched jacks in that same spot and build an effects loop for the delay path? That would be fun - you could stick whatever you'd like in there.

Something like this on the delay path would be pretty cool:








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## LukeFoxes (Jan 2, 2022)

mdc said:


> Are you looking to have distortion ONLY on the delay line?
> 
> If so, looking at the schematic, the output of the PT2399 comes from pin 14 on the chip. You could pull C23 out of the PCB and build a small distortion circuit like a bazz fuss or an electra or similar single-transistor thing on stripboard and use the + and - pads as jumper points.
> 
> ...


@mdc yep! Only on the delay line, so it can still use the mixer section before the output. I see where you're going and that's a great idea for something more shoegaze-y perhaps? Not what I was going for but would be interesting!

Looking at the schematic maybe I could insert something at C7 instead, thinking a fixed drive with maybe a blend control to keep it to one knob? Or just a simple op-amp gain stage perhaps.

I'm not sure something like an Electra would work well given it would be after the buffer stage. Then again who knows until you try right?


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## Boba7 (Jan 3, 2022)

I think an Electra circuit should work well. No problem with the buffer stage before. It's a simple circuit, so easy to breadboard or even make a veroboard. I'd try a speaker cranker clone with a volume pot on the output (it just has a gain knob) so you can keep it at unity gain but still add distortion to the repeats. Put a 10n parallel with the clipping diodes if it sounds a bit harsh.


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