The Cornerstone Colosseum is a dual overdrive pedal from Italian maker Cornerstone Gear, announced on 5 July 2023. It puts two much-copied circuits in one enclosure: a Klon Centaur-style channel and a Marshall Blues Breaker-style channel, each with its own controls, and a toggle switch that swaps which one comes first in the chain12.
The pedal came about unusually. Cornerstone ran a series of polls among its followers and supporters, and the community voted for a Klon and a Blues Breaker as the two circuits to build1. Designer Emilio, who has released a number of dual overdrive pedals for Cornerstone, describes the result as based on his interpretation of those two circuits rather than copies of them1.
Two classic circuits, reinterpreted
Cornerstone is explicit that the Colosseum is not a pair of faithful clones. On Delicious Audio's product page, the builder stresses1:
"these are not faithful clones of those two circuits, but personal reinterpretations"1
The two starting points are well established. The Blues Breaker circuit is one of the timeless overdrive circuits that makers keep returning to; in a Stompbox Book interview, designer Colt Westbrook grouped it with the Tube Screamer as a circuit that is always going to be around5. The Klon Centaur, for its part, is famous for its germanium clipping diodes6.
The Klon side of the Colosseum stayed close to its source. Delicious Audio reports that it is a rather faithful replica of the original, still able to harness the sound of the original, with one important addition: the Clip blender1. The Blues Breaker side departs further, with its clipping diodes removed entirely and a revised tone control, which Cornerstone says can make it louder and brighter2.
Controls and routing
Each channel has its own Tone, Gain and Volume controls. On the Blues Breaker side, the Clean control is a mini-dial on the front of the enclosure2.
| Control | Channel | What it does |
|---|---|---|
| Tone, Gain, Volume | Both | Standard per-channel controls12 |
| Clip blender | Klon | Gradually adds saturation from two hand-selected silicon diodes1 |
| Clean | Blues Breaker | Blends the original clean signal on top of the overdriven signal, restoring touch sensitivity on pick attack and the bottom end of the clean sound1 |
| Order toggle | Both | Swaps which channel comes first1 |
The Clean control is borrowed from Cornerstone's Gladio pedals, where it is a signature feature1. You can read more about that line on the Cornerstone Gladio SC page.
A small toggle switch changes the order of the two channels, which Cornerstone presents as an easy route to a lot of tone variations1. At the back there are 4 jacks, so each side of the pedal can be connected with a looper for separate switching or placement in a larger rig1.
Clipping diodes
The Klon channel uses 1N34A germanium diodes, the same type as an original Klon, and Cornerstone measures each one and picks those with the correct forward voltage3. MusicRadar reported that the company also fitted a pair of carefully selected silicon diodes, mixable with a mini-dial2. That dial is the Clip blender: fully counterclockwise it is 100 percent germanium, fully clockwise it is 100 percent silicon2.
The Blues Breaker side has no clipping diodes at all1. According to Delicious Audio, removing the diodes and tweaking the tone controls fixes the common issues that affect the stock Blues Breaker circuit, namely low volume and a dark tone1.
Made in Italy, priced as boutique
Cornerstone builds its pedals in Italy; the company describes them as handmade there4, and gearnews reported that each Colosseum is hand built with high-end components throughout rather than mass produced3.
At announcement the pedal carried an MSRP of GBP 319 / EUR 399, with a Thomann retail price of $307.00 / £277.00 / 315.00 euros3. On the price, gearnews' reviewer wrote:
"the price is about where I would expect a boutique overdrive to be."3
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Questions
Is the Cornerstone Colosseum Klon side a faithful clone?
Not exactly. Cornerstone's designer describes both channels as personal reinterpretations rather than faithful clones, but the Klon side stayed close to the original circuit. The one important change is the Clip blender knob, which gradually blends in extra saturation from two hand-selected silicon diodes on top of the germanium clipping.
What diodes does the Cornerstone Colosseum use?
The Klon channel uses 1N34A germanium diodes, each measured and picked for the correct forward voltage, the same type as an original Klon Centaur. Two hand-selected silicon diodes are also fitted and can be blended in with the Clip blender knob, from 100 percent germanium fully counterclockwise to 100 percent silicon fully clockwise. The Blues Breaker side has no clipping diodes at all.
Can you change the order of the two channels on the Colosseum?
Yes. A small toggle switch changes the order of the two channels, so you can run the Klon side into the Blues Breaker side or the other way round. Cornerstone points to this as a source of a lot of tone variations.
Where is the Cornerstone Colosseum made?
Italy. Cornerstone describes its pedals as handmade in Italy, and gearnews reported that each Colosseum is hand built there with high-end components throughout, rather than mass produced.
How much does the Cornerstone Colosseum cost in the US?
The Thomann retail price was listed at $307.00 in July 2023, alongside £277.00 in the UK and 315.00 euros in the EU. The MSRP at announcement was GBP 319 / EUR 399. gearnews' reviewer felt the price was about where they would expect a boutique overdrive to be.
Sources (6)
- Cornerstone Colosseum Dual Overdrive (Klon + BB), Delicious Audio, 2025-04-10
- Cornerstone asked the people what they wanted, the people spoke, and the result is the Colosseum, MusicRadar, 2023-07-04
- Cornerstone Colosseum: Blues Breaker and Klon dual overdrive, gearnews.com, 2023-07-05
- Royal Antique, Cornerstone
- Walrus Audio, Stompbox Book, 2021-10-27
- Jackson Audio and Cory Wong launch the Optimist, MIDI-controllable dual overdrive and EQ that combines a Timmy and a Klon, Guitar.com, 2022-01-25
