OVERVIEW
The OPFXS DIG DEEP MK3 is an elegantly designed sub-octave pedal that feels equally at home on a gigging pedalboard and in a recording studio. Building on the legacy of its excellent predecessor, it delivers a thick, musical low end, rock-solid tracking, and a control set that rewards both quick tweaks and deep dives. The sleek silver enclosure looks boutique on a board, but what really won me over is the versatility—filling out power or barre chords with a full low end, thickening individual note runs, and can convincingly stand in for a bass when needed.
CONSTRUCTION AND DESIGN
The MK3’s sturdy, silver aluminum housing feels premium and road-ready—switches feel solid, jacks are snug, and the footswitch has that reliable sturdiness that you’d want on stage. OPFXS also gives you modern I/O and power options (USB-C for editor/updates/power; standard 9V DC with protections; MIDI In/Thru), which is unusual at this price and category.
LAYOUT AND CONTROLS
One of the Dig Deep MK3’s greatest strengths is its deep, intuitive control set. At first glance, you’ll see familiar knobs and buttons, but each parameter has been thought through to make the pedal both flexible and musical.
Knobs
- Dry – Adjusts the level of your unaffected signal. This makes it easy to balance your natural tone with the synthesized sub, whether you want a subtle reinforcement or a fully doubled sound.
- Sub Mix – Controls the overall level of the generated sub signal. Perfect for quick adjustments when you want the sub to sit under your playing or take center stage.
- –1 Oct & –2 Oct – Independent level controls for the one-octave and two-octaves-down voices. Blending them opens up everything from tight, supportive low end to massive synth-bass territory.
- Low Pass – Smooths out the sub voice by rolling off high frequencies. Essential for keeping the sub focused and bass-like.
- High Pass – Removes excessive low-end rumble, particularly useful for acoustic players or complex arrangements where clarity matters.
- Range – Determines how the pedal tracks across your instrument’s register. Great for tailoring the response to different guitars, tunings, or even non-guitar instruments like synths.
- 1st Harmonic – Shapes the harmonic content of the sub voice, letting you dial in a more natural or more synthetic character.
- CTRL I & CTRL II – Fully assignable knobs that can be mapped to different functions using the OPFXS editor (see beneath). This makes the pedal customizable for different workflows, from live performance to studio use.
Buttons
- Wave – Cycles through multiple sub waveforms, each with its own texture. Think of it as a palette of bass tones, from smooth and rounded to aggressive and edgy.
- Split – Routes the dry signal to the main output and the sub to a dedicated SUB out. This opens up advanced routing possibilities like bi-amping or sending the sub straight to a PA or mixer. For someone that works primarily in a studio setting such as myself, this is super helpful for processing the sub layer in a variety of ways.
- CTRL III & CTRL IV – Assignable buttons for toggling parameters or switching modes via the editor. It’s amazing how much funcitonality was fit into such a small enclosure, and features like this are exactly why.
SOUND QUALITY
Three things jump out immediately: tracking, tightness, and thickness. The MK3 keeps up with arpeggios, strums, and complex chord inversions impressively well, so the sub doesn’t smear or wobble when your harmony gets interesting. The low end is weighty but defined, and the filter section (LP/HP) makes it easy to sit the sub under your source rather than on top of it. Advanced functions like Dominant Notes Cut (DNC) and High Notes Cut (HNC) help tame tricky voicings and open strings; set and forget them or assign to a control for on-the-fly cleanup. Overall, it’s musical, controlled bass—not the rubbery, laggy feel you may associate with older octavers.
It’s worth mentioning that the pedal will function and sound differently depending on where it is in the signal chain. I tried it before and after fuzz, distortion, reverb, and delay, and the behavior changes based on pedal order. I have found that placing it before fuzz and distortion results in a much more reliable tracking. I’ve had tons of fun using it with my JHS Colour Box V2 for riffs and individual note runs.
APPLICATIONS
What makes Dig Deep MK3 special is how broad the use cases are:
- Acoustic & Electric Guitar: Add tasteful sub to solo/duo sets, thicken choruses, or create faux-bass lines with Split out to a separate amp/DI.
- Synths & Drum Machines: Treat it like a sub-generator—dial -1 for weight, blend a touch of -2 for cinematic oomph, and shape with LP/HP for a mix-ready foundation.
- Baritone/7-String: Reinforce riffs without mud; the Range control keeps tracking intact down low. It’s really impressive how low this pedal goes while still staying musical.
- Studio Tricks: Split the sub to its own channel for compression/EQ, automate Wave choices per section, or store 3 presets for verse/chorus/bridge workflows. USB-C/MIDI/editor integration makes it easy to standardize recall across sessions.
SUMMARY
The OPFXS Dig Deep MK3 is a versatile, modern sub-octave workstation: beautiful silver enclosure, tons of thoughtful controls, remarkably stable tracking, and an immediately “thicker” sound that flatters nearly any source. Between the editor, MIDI, Split routing, and powerful filters, it’s equally suited to acoustic guitar sets, electric rigs, synth workflows, and re-amping in the studio. If you’ve been waiting for a sub pedal that’s creative and controllable, this is an excellent choice.
ABOUT THE AUTHOR
Ian Vargo is a Music Producer, Mix & Mastering Engineer, and Multi-Instrumentalist whose work has been heard on broadcast television, nationally televised ad campaigns, award-winning films, and viral web content amassing over 30 million views. His credits include projects for Disney | ABC, Intel, MSNBC, Airbnb, EA Games, and many more.
With over 20 years of experience in the studio, Ian has contributed to major label releases (Capitol, EMI, Fueled by Ramen, Universal, Interscope, Hollywood Records) as well as acclaimed independent projects. His passion lies in helping artists translate their creative vision into professional, release-ready recordings that stand out in today’s music landscape.
Interested in working together? Reach out at ianvargo@gmail.comif you need mixing or mastering for your next project.
