Malekko Diabolik JMJ Review – Best Bass Fuzz Pedal for Guitar?

Review of: Malekko Diabolik JMJ

Reviewed by: Rating:4On December 20, 2013Last modified:October 6, 2016



The Diabolik JMJ is the rad new Justin Meldal-Johnsen signature harmonic analog bass fuzz pedal from Malekko. Justin worked closely with Malekko to fine tune their B:ASSMASTER circuit for even more low-end and a simpler control setup in a very compact form-factor. According to Malekko the Diabolik features a preset harmonic spectrum setting allowing crisp octave overtones and a very aggressive tone setting. Apparently, this sick-looking pedal has been approved by JMJ to produce the gnarly bass fuzz you’ll be hearing from his recording and performance rig from now on. But what we want to know at Best Guitar Effects is if the Diabolik JMJ is the best bass fuzz pedal for guitar as there’s nothing quite like a killer bass fuzz to really beef up your guitar tone with some crushing low-end fuzz saturation. Let’s run down the features and see how diabolical this fuzz really is in our Malekko Diabolik JMJ review.


Justin Meldal-Johnsen Signature Fuzz Pedal.

Tweaked B:ASSMASTER fuzz circuit with custom preset tone adjustments and more low-end.

Fuzz control knob sets level of the wet fuzz distortion signal.

Clean control knob sets level of the dry, unaffected signal.

Squish control knob sets level of the gated/compressed response, adjusting the character and response of the Fuzz signal.

True Bypass switching for letting your signal pass unaffected when disengaged.

Powered by 9-volt battery or 9VDC power adapter.

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Sound & Performance:

One of the great things about using effects pedals is coming up with new ways to create unconventional sounds by using pedals differently from how they’re normally intended to be used. That’s kind of the idea with using a so-called bass fuzz pedal with guitar. Justin Meldel-Johnsen mentioned in Malekko’s Diabolik JMJ intro video that he used the B:ASSMASTER on various audio sources including drums and guitar. So rather than seeing this pedal as solely a bass pedal, you can bet Justin intends to use it to process whatever he deems is in need of some Diabolik treatment. For this Diabolik JMJ review I’m primarily focusing on how the pedal responds with guitar, but just know that this fuzz is a multi-purpose tool you may find useful for mangling any audio-source you’re twisted enough to run through it.

I used a Strat with the Diabolik JMJ and ran the pedal into a dry clean amp channel, and later I used it in combination with various sources of overdrive and distortion. The Diabolik JMJ has 2 level controls, one for Fuzz and one for Clean. This typically allows bass players to blend in their dry tone with the Fuzz signal to achieve maximum punch and clarity. But this arrangement has some surprising benefits for use with guitar as well.

I started with the Fuzz and Squish rolled all the way down and the Clean signal rulled to just 9 o’clock. Around this area you’ll find the unity gain level to match the volume of your original signal to that of the pedal engaged. This gives you the entire rest of the sweep to boost your Clean signal. The Clean knob provides great utility when used alone by letting the Diabolik JMJ function as a clean boost to raise your volume level for solos or push your amp harder for overdriven distortion effects.

Barely rolling up the Squish and Fuzz knobs to around 8 o’clock brings in the fuzz sound behind your clean signal. The Squish knob needs to be set at this level or higher or else it cuts off the fuzz signal. At lower Squish settings the Diabolik JMJ sound is tighter and more defined while pushing it up mangles your fuzz sound until it’s reduced to a splatty, insane mess of fuzzy chaos. Adjust it from 7 to 8 o’clock to find the sweet spot where it produces really cool gated fuzz sounds that sputter out like a lo-fi synth cutoff. The Squish knob is highly interactive with the Fuzz control, and such a simple control layout makes it very easy to find usable sounds quickly.

Blending in your Clean signal makes it easy to push the Fuzz to disentigrated extremes while still letting note clarity peek out from the wall of noise created by playing big loose chords. When pushing the Fuzz and Squish knobs to high levels with no Clean blended in, the Diabolik JMJ seems best suited for single note lines. Try playing through the neck pickup for some really great singing fuzz tones. Adding a hint of Fuzz and Squish is great for layering your clean tones with a mild, sputtering overdrive effect that sounds fantastic. Throughout the range of sounds the Diabolik JMJ offers, you’ll notice a nice fat bottom end that doesn’t overwhelm your signal with too much bass. Although this pedal can obliterate your chords beyond recognition, it’s not overly booming and retains a very musical tonality thanks to its carefully preset harmonic voicing.

One of my favorite aspects of the Diabolik JMJ lies in how well it plays with other pedals. As