Muroidea 30p cap with alternate op amps?

[cylnplnt]

What effect does the 30p Cap in C6 have when a compensated Op Amp is being used? Specifically the OP07 and 741. Also wondering if it’s possible to damage the Op Amp this way(including if removed from LM308)?I built my Muroidea with a socket for the 30p, as I’d read you remove it with compensated op amps. I tested my pedal with and without it, with several Op Amps and felt like I could hear an effect. I am seeking more technically specific clarity. These are my anecdotal observations.

741-Worked with and with out. Preferred it with the 30p

OP07-Worked with and with out. With, it sounded and felt like a modern RAT. Without, sounded and felt more like a LM308. Preferred it without.

Knowing the LM308 shouldn’t work without the 30p, I decided to do the test with a handful of LM308s I’ve collected. Mixed results with those. They all functioned, but some sounded better with, and some without. I know there’s a lot of counterfeit LM308s around. I only have my comparison to the vintage RAT with LM308 to compare. I don’t have knowledge or a way to test the LM308s I have for authenticity. I know I like some of them more than others, and almost all of them I prefer to the OP07. However the difference is much more subtle when the 30p is removed from the OP07.

I love this build. Sounds closest to my vintage RAT of anything I’ve tried. I’ll include pics of my build. This is just the third pedal I’ve built.

 

[KR Sound]

Here you go:

ElectroSmash - ProCo Rat Analysis

Pro Co Rat Schematic, Power Supply Stage, Clipper Amplifier, Voltage Gain, Low/High Pass Filtering, LM308 Op-Amp Selection, Diode Clipping, Tone Control, Output Stage, Pro Co Rat Frequency Response, Resources

www.electrosmash.com

The Compensation Capacitor.

Bandwidth and Slew Rate are proportional to 1/Ccompensation, the smaller the cap the bigger the Bandwidth and Slew Rate. The typical and suggested value by the datasheet is 30pF (same as used in the Rat design).





The above image shows again how the high freqs are attenuated, using a 30pF cap. Using bigger/smaller caps the Bandwidth and Slew Rate will be reduced/improved.

 

[cylnplnt]

Thanks for the reply. I’d seen this but don’t have enough technical understanding to apply it. Does the cap affect Op Amps that are “internally compensated” or like the OP07 data sheet says “For most applications, external components are not required for offset nulling and frequency compensation.” I’ve read elsewhere folks say the cap has no effect on op amps with compensation. Also am I understanding correctly it’s there to “improve” the sound of the LM308, but could be a mater of preference if you use it or not? No damage is possible?