Updated Pedal: Cornerstone Gladio MK 3 D-Style Double Preamp

Updated Oct. 21, 2026  |  by Paolo De Gregorio

Continuing the Italian builder’s obsession with capturing elusive D-style tube amp response, the Cornerstone Gladio MkIII elevates the flagship double preamp that built the brand’s reputation. Designed and hand-built in Varese, Italy, the MkIII retains the core dual-channel architecture inspired by the dynamic touch sensitivity of rare Dumble-style circuits, while completely rebuilding the pedal around key player requests.

Core Voicing Consistency
The MkIII preserves the fundamental dynamic separation between its two preamps. Channel 1 remains the smooth, transparent, edge-of-breakup voice inspired by Robben Ford, delivering clean-to-dirty breakup based purely on pick attack. Channel 2 continues as the midrange-forward, harder-clipping voice inspired by Sonny Landreth. Both channels now feature dedicated Compression toggles to switch between tight/controlled and open/touch-reactive feel.

Critical MkIII Upgrades
Where the original Gladio (retired in 2022) relied on internal adjustments and fixed routing, the MkIII exposes full control to the front panel and expands hardware flexibility:

• Channel 2 Ratio Control: A major overhaul to the harder-clipping channel, this clean blend mixes the dry input signal in parallel with the overdrive, restoring transient attack and string definition without sacrificing gain.
• External Bass Control: The bass response—previously locked behind an internal trimpot—is now an improved, external front-panel knob for instant low-end tailoring.
• 30V Internal Headroom: An internal charge pump steps up standard 9V power to a massive 30V rail, expanding dynamic headroom so notes bloom naturally without flattening under heavy gain.
• 4-Jack Independent Routing & Remote Switching: Features four audio jacks, allowing you to split the two preamps completely to place other effects between them or run them into separate switcher loops. A dedicated Remote jack accepts standard latching footswitches for hands-free switching.

By replacing internal trimpots with front-panel controls, introducing parallel clean blending to Channel 2, and adding 30V internal headroom with 4-jack routing, the Gladio MkIII turns a sought-after D-style engine into an uncompromised, modern rig anchor.

 

—

Cornerstone Gladio MK I

Whether you call them D-Style pedals or Dumble-inspired overdrives, gain stompboxes attempting to emulate the voicing of the ultra-rare Dumble amps are probably the second most hyped overdrives after the (still unreachable) Klon clones.

Based in Varese, Italy, Cornerstone Gear is a family-owned company focused on designing and hand-building guitar and bass effects pedals, and so far it’s been squarely focused on the gain realm, with the exception of a compressor.

The Cornerstone Gladio is a versatile D-Style double preamp featuring two independent channels with different voicing, which allows for extra flavors when combined together. Presented as “a realistic tube-compression preamp able to take the sound into saturation [and yet] retaining a rich touch-sensitive response and realistic compression,” the Gladio was built with in mind the tone of artists like Robben Ford or Eric Johnson.

This is how the builder describes Channel 1:

[It] delivers smooth and creamy sounds (inspired by songs like Robben Ford’s Cannonball Shuffle). It’s really transparent and with a round touch-sensitive response. […] A toggle switch called COMP lets you choose between two different compression levels.

Channel 2, on the other hand:

[is] designed to offer a special hard clipping sound pretty much inspired by Sonny Landreth’s tone. […] A toggle switch called JAZZ/ROCK, which should not need presentations [referring to the similar switch found on Dumble Amps].

An extra toggle switch (S/D) lets you stack the two circuits on top of each other (D mode), while in S mode activating one channel automatically deactivates the other.

Lots of buzz about this pedal, it seems like every YouTuber wants to review it. We added it to our popular article about the best D-Style pedals.

A DOUBLE PREAMP

WHY A PREAMP:
We’ve always been fascinated by the sound of great artists like Robben Ford or Eric Johnson (to name a few) and it’s always been our dream to recreate those sounds in a pedal. To do that, we soon realized that the key was to be able to offer something close to the amps they were using.
The design goal had a name: Dumble.
This is the reason why GLADIO is not just an overdrive; it’s a realistic tube-compression preamp able to take the sound into saturation still always retaining a rich touch-sensitive response and realistic compression.

WHY A DOUBLE PREAMP?
It’s all about versatility. GLADIO has two independent channels with totally different voices, which combined together offer an even wider range of sounds.

WHAT ABOUT CHANNEL 1?
The 1st channel is able to deliver a smooth and creamy sounds (inspired by songs like Robben Ford’s Cannonball Shuffle). It’s really transparent and with a round touch-sensitive response that helps enhancing the playing. Controls (Gain, Tone and Volume) are self-explaining and there’s a toggle switch called COMP to choose between two different compression levels.

WHAT ABOUT CHANNEL 2?
The 2nd channel is designed to offer a special hard clipping sound pretty much inspired by Sonny Landreth’s tone. Controls are all self-explaining and there’s a toggle switch called JAZZ/ROCK, which should not need presentations.

WANT MORE VERSATILITY?
The Gladio is eequipped with a special toggle switch to choose between two different switching modes.
“S” which stands for “SINGLE” and “D” which stands for “DOUBLE”.

In Single mode you can use only one channel at a time; that means that pressing the footswitch of one of the two channels makes the other turn off (without dancing the tip tap).
In Double mode you can stack the two channels to reach a huge fat Dumbl-esque sound.