Product Overview
The 2024 version of the JunkTrunk has some circuit changes and minor layout tweaks.
Overview
The Agent 00Funk and BrownDog were produced by Australia’s ChunkSystems and marketed to the bass playing
community (Bootsy Collins was apparently a big fan) around the late 00’s to early 2010’s. I’m not sure if they
went completely out of business but the pedals seemed to have been discontinued and only show up on the used
market. That makes for ripe DIY projects!
The JunkTrunk is based on the 00Funk. It’s an envelope filter with a number of familiar elements and some
thoughtful design execution. Plus, it doesn’t require any out of production parts so the overall build price is
reasonable. It’s very responsive to bass and lives up to its funk moniker. Combined with the GasTank project it will
even deliver some bass synth type tones.
The LED bypass system used in the previous version has been removed to make the GasTank compatible with
the SSBP and SSABP switching boards.
Controls
• PITCH: Sets the frequency of the swept filter from low to high.
• SMOOTH: Sets the length of the swept filter. CCW is short (“jerky”) and CW is long (“smooth”).
• SQUELCH: Adjusts the resonant peak of the swept filter. CCW is low resonance (“subtle”) and CW is high
(“mayhem”).
• SWEEP: Determines the range of the swept filter. CCW is narrow, CW is wide.
• D/U: Determines the direction of the filter. Left is down, right is up.
• ENV (optional): This jack is used to connect to the Gas Tank (bass fuzz) to allow for more dynamic response
in the filter when both pedals are used together. More details in the Notes section.
The potentiometer controls in this circuit have some dead spots at the extremes. They don’t all “do something”
at every setting and sounds need to be dialed in. Particularly, you’ll find the Sweep control settings will have a
certain range depending on where the Pitch control is set. The Pitch control doesn’t really do anything when it’s
all the way up. Smooth and Squelch also share some interdependency with the other controls, too. IOW, when
you encounter this your build is probably working correctly. It’s the nature of the design and takes a little getting
used to.
The JunkTrunk (and GasTank) are primarily bass effects. If you do build the JunkTrunk for guitar, I suggest trying
smaller values for C2 and C3. This will adjust the center frequency of the filter. Suggested values are 1n through
6n8 (use the same value for both caps). Experiment and find what you like best. The GasTank doesn’t sound that
great as a guitar fuzz, you can get some neat synth-like settings when you combine it with the JunkTrunk.
This demo will give you a really good idea of how the Agent 00Funk and BrownDog operate and sound: https://
www.youtube.com/watch?v=OEHMyviwZMA&t
