Afterlife Nasty Clipping

[ogguitar]

Got the Afterlife on my breadboard with the Ghost Note mod, and I'm getting clipping that sounds like a starved voltage fuzz/OD of sorts, and the sustain and sensitivity controls don't seem to work properly. I'm a bit puzzled about this one as I've double checked the circuit, connections, and component values several times. Any possible leads or tips are greatly appreciated. Cheers!

[midwayfair]

Post pictures and voltages please.

probably want to link to the mod, too, even I don't remember exactly where that post is ...

[ogguitar]

Here you go. Thanks for the help!

https://drive.google.com/file/d/1jJo9mGtU8UiblM5ofhBwo4obNSCsGC2R/view?usp=sharing

My IC voltage readings
1 7.53
2 8.90
3 4.37
4 0
5 8.93
6 6.77
7 7.62
8 9.04

Mod is R7 (47k) swapped for 24k in series with B50k pot as you've described. Here's how I hooked it up

For anyone wondering, here's how you do the Ghost Note mod:

Connect lugs 2 and 3 of the pot. Solder one side of the resistor to lugs 2/3, and the other side goes to the PCB. A wire from lug 1 of the pot goes to the other resistor hole on the PCB. Order doesn't matter. You could use a 100K pot without the limiting resistor (or even larger) instead if you like, but I found the 50K + 24K gave plenty of range.

I used a linear so that noon was the original value, but feel free to deviate!

[midwayfair]

pin 5 is connected directly to Vb in the schematic, which should put 4.5V on that pin -- you have it almost at 9v. Trace all your power connections starting with the 9V.

[ogguitar]

Ah yeah I had R9 going to VB instead of to IC 4. Thanks a bunch!

There still seems to be a fair bit of breakup (much nicer sounding now though) at higher sustain levels, but I've been using a guitar with pretty hot humbuckers. For now I've just turned the sensitivity knob all the way down and backed off the sustain until it cleans up a bit. The compression sounds quite nice!

[ogguitar]

Just in case anyone ends up following this, I addressed the clipping primarily by using a different optocoupler. The cleanest ones I have seem to reduce overall volume a fair bit. Unity is basically max on the A100k pot, but it's ok imo because I'm never really looking for a compressor to boost my signal. Though if anyone has tips on how to increase the make up volume available I'm all ears.

I also stumbled across this write up which I found very useful to make the circuit a little friendlier to different opamps, among other things.
https://atomiumamps.tumblr.com/post/158891400886/hollis-flatline-compressor-modsupdates-ive-built

Lowest noise I have is a NE5532 which is dead silent even with everything exposed on a breadboard. The LM833 has lower noise than the TL072 as well, and it seems to be the squishiest of the bunch so far. I'm not sure which I prefer yet. I've also swapped the bridge diodes to 1N5817 as I have a few extra, and I want to save the germaniums for another project.