Have you ever wondered how an Octavio would sound without the octave up? Me too and then I made the MXR Octavio Switch Mod, for the limited edition JHM6 Jimi Hendrix version from 2018 (?).
It’s kind of funny, because on the latest 2019 JHW2 psych mini octavio has a switchable octave, but the newer main-line MXR octavio M267 from late 2019 doesn’t.
Anyway, we’re not here to complain about what is or could have been. Let’s talk about the mod, shall we!?
Above you can see a schematic of the Tycobrahe Octavia. It’s not the MXR Octavio, but that’s not important to explain the mod. The octave up effect is achieved with the rectifier at the end after the 33uF cap. The 42TM022 transformer together with the two 1N34A diodes form a rectifier, which will basically double the frequency of the signal. Hence, the octave up.
If we’d simply block one of the diodes, the frequency would stay the same and we only have fuzz.
Seems easy, doesn’t it? It kinda is, but there’s one pitfall I want to warn you about, because I stepped into it. Severely.
The images below show all the necessary places and connections you need to touch.
Here’s the thing you have to be careful with:
At first, I tried to cut one leg of one of the diodes and solder a wire directly to it. Unfortunately, those 1N34A diodes have housing made of glass or something similar and it broke apart.
So what I recommend is to completely desolder one of the diodes and solder it onto a small piece of veroboard with one row. This will physically support the diode. You can then solder your wires a to that veroboard with a little less worry.
That’s it for the MXR Octavio Switch Mod. I hope you enjoy it. Let me know, how it worked for you.