As Seen On TV Crunchy Boost ….. a simple overdrive that sounds great

as seen on tv pedal

My Zombie Screamer is really good for heavier overdrive sounds but I wanted to design a simple overdrive that had a wide range tonal control(treble boost and cut), that could be used as a simple clean boost…through light overdrive….. all the way to heavier distortion. It uses junk-box type parts and is easy to get up and running. The only part that is a little unusual is the 5k tone control pot. I say this because ideally, it would have an anti-log taper. A linear pot will work fine. I like the sound and it can be tweaked in a number of  interesting ways. Decreasing R3- will increase your max overdrive level, you can go to just two diodes instead of two sets of series diodes for clipping, R10 can be made larger( softer clipping) or smaller(harsher clipping).  The tone control can be modded also. You can swap the pot connections to C6 and R8(wiper will now go to C6 and the high side connection will go to R8). This changes the curve some. Another option is to tie C6 to the top of R8 and then connect c9(you may want to adjust this value) through the tone pot(as a variable resistor). This only gives treble cut but the overall gain is higher giving more intense distortion.

Schematic:

as seen on tv2

Alternate Schematic

(more drive for low output single coil pickups)

as seen on tv3

Yet another version which is hybrid FET/Transistor

(best range of overdrive)

as seen on tv4

Surface Mount Circuit Board:

IMG_20150519_122103308

 

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Minimized implementation of the Tube Screamer

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)

Simple FET Overdrive Guitar Pedal

This is a really simple design for an overdrive pedal. My goal was very low noise, low power consumption and an overdriven amp type distortion sound. The circuit uses a very low noise OPA1652 to boost the input and control overdrive level. The signal then goes into a single voltage starved Jfet operated at 5 volts to create the distortion. The biasing of the Jfet is fairly critical, in order to make the distortion symmetrical. If other  Jfets are used, one might have to tweak the bias resistor values. The pedal is very low noise and provides signal boost – all the way to heavy distortion. What I like about it most is that the pedal is very responsive to playing dynamics, allowing for subtle all the way to crunch type distortion depending on how aggressive you play lines or chords.

In the schematic, Q1 and Q3 are generic PMOS and NMOS fets- nothing special here – many will work. The PMOS is used as  reverse polarity protection. The NMOS is for the LED activation. Also the 5v regulator can be anything – even a zener if you like.

Schematic:

https://circuitsaladdotcom.files.wordpress.com/2012/09/fet-overdrive1.gif

Pedal Pic:

https://circuitsaladdotcom.files.wordpress.com/2012/09/fet-overdrive.jpg

Sound Sample:

https://circuitsaladdotcom.files.wordpress.com/2012/09/overdrive-demo.mp3