Welcome to the rather wacky world of analog octave, Z.Vex style. The Jonny Octave! This pedal will convert your guitar’s output signal to either one octave up or two octaves up, but only under the right circumstances. This tutorial should help you achieve the best octave sound.

First of all, it’s helpful to understand just how analog octave-up circuits work. Nearly all of them operate on the same general principle, that of full-wave rectification. What’s that? Well, it looks something like this:

Z. Vex starts with a very simplified wave representing your guitar’s string swinging back and forth once. This is what the output of your guitar would look like with your NECK pickup and a note struck near the 12th fret (where analog octave-up circuits get their best sound):

Fig.1 Sine-like wave.

The Jonny Octave boosts that signal, runs it into a phase-splitter (you don’t need to understand that part) and then puts it through a full-wave rectifier, something like a ring-modulator, and sends the result through a transformer. That takes the lower half of the wave and flips it up over the middle. Then it looks like this:

Fig.2 Full-wave rectified signal, one octave up.

Note how it got smaller. There’s a gain stage to boost it back up after that. Count how many peaks and valleys it has now... the sine wave in figure 1 had only one peak and one valley. In the same period of time, the new waveform (1 octave up) has two peaks and two pointy-looking valleys, or two times the frequency. Does it sound clean? Not really, but it isn’t fuzzy, it’s more like half smooth and half pointy, which sounds slightly jaggedy.

For the 2nd octave up, the Jonny Octave does it again!

Fig.3 Second time through a full-wave rectifier, resulting in two octaves up.

It got smaller again... once again, there’s a gain stage to boost it back up. Now it’s really funny-looking, and it sounds pretty strange too, but if you count the peaks and valleys, it’s got 4 of each, making it two octaves higher (4 times the original frequency).

Some things you can do to help make the octaves stand out are:

1. always use your neck pickup for notes near the 12th fret.
2. experiment with your middle pickup or lead pickup for notes much higher than the 12th fret.
3. try turning down your tone control to make the octave sound more prominent, if that helps. Sometimes it does.

Your Jonny Octave comes with 4 trimmer controls inside that are arranged like this:

Fig.4 Jonny Octave guts.

The circuit block diagram below shows where these trimmers come into play. Each one controls a gain stage.