Apex
Distortion
top of the food chain
Apex
Distortion
The Apex Distortion has been retired.
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Apex Distortion is a versatile distortion pedal which was originally inspired by a particular LM308 rodent pedal. The goal was to create something new, while still paying homage to the original. This is not a clone. It is a reimagination of a classic. Top of the food chain. The Apex predator.
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History
I decided to challenge myself to design a pedal around that chip with a circuit inspired by the said rodent pedal. So… I found some LM308s and got to designing. The pedal went though many revisions, in fact I had a version that I almost released. I really liked it, but I felt after playing it at band practice a few times, I thought I could do more… it needed more toanz for my snobby ears. I wanted to improve some aspects of the original by increasing its versatility, improve the gain range, smooth and thicken the tone, while still maintaining some bite.
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Circuit Breakdown
First things first, I love boosting the RAT with another drive, bit so I added a JFET front end gain stage. JFETs are great because they react extremely well to the dynamics of your playing… dare I say it?... are very amp-like in their character. Next is the LM308 primary gain stage. I completely changed it’s voicing. I wanted a nice low punch with crisp highs and it had to preform well in both low gain and high gain situations. Next is the clipping section. I wanted to a blend of smoothness and crunch so I combined a mixture of diodes and an LED. Up next, the tone stage, which similar to the RAT, functions as a classic low pass filter however it is reversed so to the left is darker, right is brighter. Finally in true classic form a JFET buffer which also adds some color as it saturates.
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I’m really digging the result, I hope you do too.
Controls
Power Requirements:
9volt - Center Negative 2.1mm Barrel
Higher Voltages will for sure damage the pedal!!
Current Draw: ~8mA
No Batteries
Volume:
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Tone:
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Gain:
LED Brightness
Trimmer:
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Bias Trim Pot:
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Controls the output volume of the pedal. It can get really loud! Set the Gain to minimum and you have almost a clean boost.
Low-pass filter. Turn to the left for a darker tone and to the right for a brighter tone.
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Controls the amount of distortion.
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Inside you will find a trimmer right next to the foot switch. This trim pot allows you to adjust the brightness of the LED. You like to be blinded by the light? Turn it up! You find yourself putting a piece of tape over the LED on your pedals? Turn it down.
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Just don't mess with it. But if you did... stick your DIMM in those two little holes and turn the trimmer to about 12.12 volts.
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Demo Videos
Interactive Demo
Schematic
Here is the schematic for the Apex Distortion. The goal here was to redesign a rodent inspired pedal, while keeping the circuit topology fairly close to the original and using the LM308 chip.
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You can use this as a starting point and tweak the values to your taste.
Some ideas:
- Lower or even remove C15 decrease the low end going into the circuit
- Reduce C3 to increase high end going into the circuit. However, be aware that increasing some of the high end going into the clipping may cause the notes to fizzle out as they decay. Notes don't decay evenly, and sometimes you can hear that in clipping circuits as little... well for lack of a better word... farts as the notes decay.
- Change the values of R7, R8, C6, C7. These components form a high pass filter in the feedback loop of opamp. Check out all the different opamp based pedals out there and notice how these are very different. They have huge impact on the overall sound and feel of the circuit. You can have a lot of fun here and really tailor to sound to what you are looking for.
- C8, R9 and the diodes shape hard clipping. The world is your oyster here.
- The Tone potentiometer, R10, and C9 are the low pass filter. You can go back to the traditional pedal here or modify however you like.
*Note: none of the suggested changes have been tested, they are just starting points for tweaking. So... get out the breadboard and have some fun. Make something new, or just tweak the values a little to tune to your tastes.
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Enjoy!
