OPFXS Dig Deep Sub Octave Mk3

The OPFXS Dig Deep Sub Octave Mk3 is an octave-down pedal from the Italian maker OPFXS. It generates a rich, monophonic bass line from your guitar signal, which Delicious Audio describes as transforming a thin tone into a massive, layered sound without affecting the integrity of your original dry signal¹. The key idea is that only the lowest note you play is pitched down: Guitar Pedal X's review notes that lower strings receive octave processing while upper strings remain unaffected². That makes it, in Guitar Pedal X's words, "perfect for delivering basslines - so you can supplement your melodies with some simultaneous bassline action"².

What it does

The Dig Deep MK3 is a monophonic sub-octave pedal: rather than pitching the whole signal down, it generates a rich, monophonic bass line from your guitar signal, with lower strings receiving octave processing while upper strings remain unaffected. OPFXS says that makes it perfect for delivering basslines, so you can supplement your melodies with simultaneous bassline action, transforming a thin tone into a massive, layered sound without affecting the integrity of your original dry signal¹².

Because the effect is monophonic, it suits single-note lines and low string work best: the pedal builds its bass line from the lowest note detected, so the dry guitar above it stays intact²¹.

Controls and features

Delicious Audio sums up the control set this way: "Five primary knobs and four assignable controls (via a dedicated editor) let you fine-tune everything from the mix of the -1 and -2 octave signals to the precise filtering of the bass tone"¹. In practice that means you can blend the octave-down and two-octaves-down voices independently and shape the resulting bass tone with filtering, rather than accepting a fixed sub sound.

Beyond the panel, the MK3 offers:

3 user presets for storing different bass line settings¹
Full MIDI implementation for integration with a MIDI-controlled board¹
A USB-C editor for deeper editing and the four assignable controls¹

How it compares

Delicious Audio's review of the MK3 places it among octave-down pedals, describing it as an advanced and cutting-edge octave-down pedal that generates a rich, monophonic bass line from your guitar signal¹. The publication's overall verdict on the MK3: "OPFXS's Dig Deep MK3 Sub-Harmonic Octaver delivers fantastic Separated Monophonic Basslines"¹².

For a wider look at where the MK3 sits among pitch-shifting effects, see Octave & Pitch Pedals.

Videos

**OPFX DIG DEEP MK3 & MK1 Demo // The Pedal You Did Not Know You Need!**
Philip Czarnecki and OPFXS

**Finally Play Your Guitar and Bass lines At The SAME TIME | OPFXS Dig Deep mk3**
JayLeonardJ

Questions

What does the OPFXS Dig Deep Sub Octave Mk3 do?

It is an octave-down pedal that generates a rich, monophonic bass line from your guitar signal. Only the lowest note played is processed and pitched down, so chords and melodies keep their original character while a sub-octave bass line runs underneath. Delicious Audio describes it as transforming a thin tone into a massive, layered sound without affecting the integrity of the original dry signal.

Can the Dig Deep MK3 process only some strings?

Yes. Guitar Pedal X's review notes that lower strings receive octave processing while upper strings remain unaffected, which lets you play a melody on top while the pedal supplies a simultaneous bass line from the lower notes.

Sources (2)

New Pedal: OPFXS Dig Deep Sub Octave Mk3, Delicious Audio, 2025-10-22
Guitar Pedal X, Guitar Pedal X, 2025-09-02