There are no big secrets about the most popular type of Overdrive / Distortion circuits. As can be seen with the thousands of 'Mods' and home brew copies of the Tube Screamer® as originally designed by Mr. S. Tamura. Basic non inverting clipping circuit: <img src="https://api.walster.co.uk/uploads/file-1753725912918-970663967.jpg" /> Mixing the input and output signal of the clipper circuit preserves the original dynamics of the input signal. Add some carefully selected high and low pass filters and that's pretty well it.. Not exactly Rocket Science! My TubeDrive is specifically designed to drive Valve (Tube) amplifier front ends and employs a classic silicon diode clipping circuit and a JRC4558D Op Amp. With full protection circuitry. And as reliability and road worthiness are a standard requirement for all my designs, i am currently working on a stainless steel housing for the unit Here is the PCB: <img src="https://api.walster.co.uk/uploads/file-1753726082541-293887565.jpg" /> TUBE SCREAMER® is a registered trademark of Hoshino Gakki Co. Ltd.