The Void Ripper got its start by a lucky coincidence that turned into a really fun project. I was staying with a friend in San Luis Obispo and had brought some pedals with me to work on. His brother was in town, and after seeing my work, he asked if I could make him a pedal that sounds like Electric Wizard. At this point I was only vaguely familiar with the band, so I said I would look into it. This is where I first heard about the Hyperfuzz, and after some quick reading, I saw that it was based on the Univox Superfuzz. It was just my luck that I had just built a clone of the Superfuzz and had it with me! I caught him right as he was heading out and told him to wait while I plugged the pedal into my rig. The excitement on his face when I turned on the mid-scoop was priceless. I had my first pedal commission on the spot. I bought a premade PCB and spent a few hours learning how to make graphics. Getting the distortion over the lettering just right took endless tweaking, but was well worth the effort.
This commission was meant to be a one off, but after posting some demos, I had a quite a few people express interest. At this point I had designed a few more pedals, so I decided make my own PCB and to add it to the roster. Not wanting to sell a direct clone, I set out to include some mods to set it apart from other variants. Here's the technical detail:
First, the JFET buffer and discrete op-amp input stage has been replaced with an TL072 dual op-amp. This eliminates the need for a power rail capacitance multiplier to make up for the discrete op-amp’s poor noise rejection, and the TL072 works just as well as a buffer. This will lead to a slightly different frequency response from the original and marginally affect the clean boost tone, but this is negligible because the sound of this pedal depends much more on the following stages. The change was made to reduce the part count so that the circuit could fit in a smaller enclosure with through hole parts. The typical buffered bypass has also been converted to true bypass.
The mod at the center of this pedal is the octave-off switch. The octave is created by an active rectifier formed by the three transistors shown in the figure below. Q1 is set up as a phase splitter, creating a buffered signal at the emitter and an inverted signal at the collector. These two signals are fed into a differential pair formed by Q2 and Q3, which each conduct in turn so that the negative half of the wave is made positive, a process called full-wave rectification. Flipping the lower half of the signal effectively doubles the frequency, creating the octave effect*. In order to remove the octave, all that needs to be done is to ground one of the inputs to the diff pair, shutting off one side and turning the other into a Class A amplifier. This has the side effect of boosting the gain quite a lot, but the clipping diodes in the following stage make sure that the overall volume level remains the same.
Analog octave-up pedals produce the strongest octave when the signals hitting both sides of the rectifier are closely matched. The Univox this is based on has a trimmer in this stage to perfectly balance each side, but in this pedal R9 and R10 in the phase splitter have different values and amplify the signal asymmetrically, reducing the octave intensity. This presents the unique opportunity to change the octave-off character depending on which side you turn off. One side sounds like the original octave mode, and the other has quite a bit more sag and warmth. The mod conjures up new, very usable tones from a pedal that is known for its distinctive, but somewhat confining sound.
The FZ-2 has three voicing modes: a mid scoop, a mid emphasis, and a clean boost mode that bypasses the octave and fuzz. The Void Ripper also includes a fourth mode that mixes the first two together, inspired by a hardware bug in a popular clone.
This project inspired some fun exploration of unfamiliar genres for me, and led to another custom pedal for a friends band! More on that soon.
*A very similar circuit is used in compressors like the Dynacomp/Ross and our Astronomer, except the rectified voltage is smoothed out with a capacitor to create a representation of the signal's RMS level. In the case of the Astronomer, the octave signal can be used to control the compression without being smoothed out, creating its signature distortion.