The Tube Screamer is a classic all around great sounding distortion, even though the stock circuit is not very complex, by eliminating the JFET bypass switching and utilizing true bypass you eliminate quite a few parts. Even more, you can eliminate the input and output follower stages a number of coupling caps and bias resistors. With just one op amp and less than 25 parts, you can make a tube screamer that sounds just great. In my implementation, I changed some values in the filter section to suit my taste and on the first stage I used BAT46 shottky diodes. These diodes have substantial reverse leakage- so you have to lower the impedance of the feedback pot and resistor that controls the the drive gain. That is why I used a 50k pot and 100 ohm resistor. I used the shottky because they start to clip much sooner and you can get a really insane amount of overdrive. Regular silicon diodes work just fine. The original stock values can be used and can be found on the web.
Schematic:
Demo (coming soon)
Circuit Salad 
Very informative publish. Thanks for discussion Bookmark it as favorite.
I built this- on the breadboard it was a little dark and hissy, so I changed the input cap to 22nF, output to 100nF, 220 nF tone cap to ground, and added a 51 pF across the first op amp feedback. Now it has the tone I wanted, and no hiss. Its boxed now, very happy with it.
neat…yes I have changed a couple of values for mine also. The 51pf is probably a good idea. Not sure the input/output matter much. The tone cap will make a difference also C4 is something to look at. If you make it smaller you will get mid and high boost. Finally C8 can be smaller if desired.
Here is a link to shots of my build:
I love it! The form factor is really cool. What is the enclosure part #
This is a Hammond 1590LB, about 2″x2″x1″. If you click on the photo it should take you to my Photobucket, you can see a few more shots there.
saw those nice… I like this form factor. I am going to try using this box. Once you give up the battery(which really no one needs) you eliminate some hassles and simplify your circuit. Next we need to go to a double instead of a triple for space(can do this with alternate bypass topology). Will those jacks fit side by side on one face(the top for example)? Just thinking about what you can cram in but have a standard symmetric layout.
I’ve built 4 with this box. Here are the other 3:
I’m working on a perf layout now for your PT2399 delay, its a little more complicated than the Zombie, but I’m just about there. I was originally going to build a Cave Dweller, then found your circuit, so the choice was clear.
The DPDT will save 0.2″ compared with the 3PDT (using low profile switches). Others have used non-standard layouts with this box, but I prefer this. I tried Neutrik jacks, love their quality, but think the plastic jacks give more flexibility- they are ⅝” square, and a little under 1″ depth- so yes they could be placed on the face. However, then you get into other problems with pot and power jack placement.
E-mail me if you would like to continue this.
russrutledge@comcast.net
Russ