About BeefBox

The distortion pedal features five primary sections–from left to right on the schematic: the preamplifier, two clipping stages, the tone control stage, and the volume control stage. The final section is an amplifier we quickly put together. 

When the raw signal meets the first stage, two modifications of note occur. The low pass filter formed by C10 and R9 prevents obnoxious high frequencies from passing through the pedal. The schematic I modified suggests that R9 be 470k, so to attenuate signals of around 600 Hz and higher, I use a 560pF capacitor, calculated by using the following equation: 

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Of course, higher frequency signals will not be completely cut out, which is actually preferable as they are wanted under certain circumstances (pinch harmonics, etc). Signal amplification also takes place here, thanks to the 2N5088 NPN transistor Q4. I note that the transistors serve as gain-recovery components after each stage. 

The signal meets the second stage, where most of the fun happens. Diodes D4 and D3 function as a clipping circuit, cutting off the signal at around .3V of its peaks. Even better, this occurs twice, as we clip the signal once again in the third stage of the pedal. The clippers make the Beef Box’s sound possible through harmonic distortion. In the process of clipping, these stages introduce oscillatory modes of frequencies that are both integer and non-integer multiples of the fundamental frequency. These superimposed frequencies make the tone sound “dirty,” as opposed to the “clean” tone that is often associated with superpositions of integer harmonic frequencies. In other words, what we are hearing is a combination of notes that are both equal and unequal in pitch to the strummed notes. 

The signal is about to meet its maker, but not before passing through the variable highpass filter formed by C9 and R8, and a 100k pot. For higher frequencies to pass, one would set the pot to its maximum level, thereby cutting out the pot’s resistance entirely. To calm these frequencies, one would set the pot to accept the full 100k resistance. Finally, the amplified, distorted, distorted again, attenuated, and amplified again signal encounters the volume control region, formed by a simple 100k pot in series with the output line.