The Diamond Cornerstone is the kind of pedal that makes a fairly simple promise: put the sound and feel of a classic British amp into a compact box.
There are plenty of pedals trying to do exactly that. I have played quite a few of them over the years, and the basic recipe is usually familiar. You get some crunchy mids, enough gain for classic rock, and hopefully something that feels at least vaguely like a cranked amp.
The Cornerstone does that too, but there is one thing that makes it stand out.
Dynamics.
This pedal feels unusually open and responsive. Instead of turning it on and immediately feeling like the sound becomes smaller or more compressed, the Cornerstone can actually make the whole rig feel bigger and more alive.
That ended up being the main takeaway from my Diamond Cornerstone review.
There is one important thing to mention before going further: the original Diamond Cornerstone is now discontinued. Diamond Pedals is active again, but the Cornerstone is currently part of the company’s legacy range. That means you will most likely be looking for one on the used market.
If you find one, though, I think it is still a very interesting pedal.
What Is the Diamond Cornerstone?
The Diamond Cornerstone is a British-style overdrive and distortion pedal built around multiple gain stages.
At first glance, it looks pretty simple. You get Volume, Gain 1, Gain 2 and Mids controls, plus a Bright switch.
The interesting part is what happens between Gain 1 and Gain 2.
Gain 1 behaves somewhat like the preamp gain of an amplifier. Gain 2 is more like adding power amp saturation. More importantly, the two controls interact with each other.
That means you are not simply choosing how much distortion you want.
Changing Gain 1 also changes the way Gain 2 behaves, so you can move between different flavours of overdrive and distortion rather than simply making the same sound dirtier.
It is a clever idea, and once you start turning the knobs, it becomes one of the most useful things about the pedal.
You also get a Mids control for shaping the midrange and a Bright switch that changes the high-frequency character. Both become particularly useful when moving between different guitars and amps.
The Cornerstone is true bypass and can run from a standard 9V power supply or a battery.
On paper, none of that sounds ridiculously complicated.
In practice, there is a surprising amount of range.
How the Two Gain Controls Work
The interactive Gain 1 and Gain 2 controls are really the heart of the Diamond Cornerstone.
Gain 1 gives you more of that preamp-style drive. As you increase it, the sound becomes more saturated in a familiar way.
Gain 2 feels different.
It adds something closer to the sound and response of a power section being pushed harder. Depending on where Gain 1 is set, Gain 2 reacts differently.
That gives you much more control over the character of the distortion.
You can make the Cornerstone relatively clean and open. You can get crunchy British rhythm sounds. You can push it into thicker rock tones. And you can decide whether most of that character comes from the more preamp-like Gain 1 side or the more power-amp-like Gain 2 side.
That distinction is obviously an approximation rather than literally having a tube preamp and power amp inside the pedal, but from a player’s point of view it makes sense.
You hear and feel the controls doing different things.
And that makes dialing in the pedal much more interesting than simply having one Gain knob.
My Diamond Cornerstone Test Setup
I wanted to see how the Cornerstone behaved with different guitars and, perhaps more importantly, different amplifiers.
For the main test I used two amps: my Revv Dynamis 7-40 and a BOSS Katana 50.
The Revv Dynamis was running into my Two Notes Torpedo Live. I normally like setting the Dynamis somewhere around that clean-to-crunchy area, which makes it a good platform for testing drive pedals.
I also used three different types of guitar.
The first was my Fender Road Worn ’50s Stratocaster. Then I moved to a Telecaster, followed by a humbucker-equipped guitar.
The idea was not to find one perfect Cornerstone setting.
I wanted to see whether I could move the same pedal between quite different rigs and still make it work.
That turned out to be one of its strengths.
Diamond Cornerstone With a Stratocaster
Starting with the Strat and the Revv Dynamis, I set everything on the Cornerstone around noon.
The British character was immediately obvious.
There is that familiar crunchy midrange and slightly aggressive edge you would expect from a pedal living in the classic British amp world. However, it did not feel overly compressed or artificially distorted.
That is important.
A lot of amp-in-a-box pedals can produce a convincing EQ curve, but the feel under the fingers tells a different story. You hit the strings and immediately notice that everything has become slightly smaller.
The Cornerstone did not give me that impression.
As I started changing Gain 1 and Gain 2, the different roles of the controls became much clearer. Instead of simply adding more and more saturation, I could adjust the texture of the drive.
That makes the pedal much more versatile than the simple front panel might suggest.
Using the Cornerstone as a Low-Gain Boost
One of my favourite discoveries during this Diamond Cornerstone review was how well the pedal works at lower gain settings.
This is not just a pedal for pretending your clean amp is a cranked British stack.
You can turn the gain down and use the Cornerstone almost like an amp-enhancing boost.
That became especially obvious with the BOSS Katana.
On a very clean setting, the Katana can sound almost too clean. There is nothing necessarily wrong with the sound, but it can feel a little sterile compared with an amp that is starting to work harder.
Turning on the Cornerstone at lower gain settings gave the sound more liveliness and more oomph.
More importantly, it seemed to improve the way the amp responded to my playing.
I could play softly and keep things controlled, then dig into the strings and get considerably more aggression.
That dynamic response is probably the biggest compliment I can give this pedal.
It does not just add distortion.
It changes the way the rig feels.
The Cornerstone With a Telecaster
Things became even more fun when I switched to the Telecaster.
I went back to the Revv Dynamis without changing the amp settings and started again with the Cornerstone controls around noon.
This combination had that cranked-amp quality I really like.
You know the feeling when an amp is pushed enough that every note seems to have a little extra energy behind it? That was what I was getting here.
The Tele still sounded like a Tele.
The Dynamis still sounded like the Dynamis.
But the whole thing became bigger, more aggressive and more responsive.
That might sound like a small distinction, but I think it is actually one of the hardest things for drive pedals to get right.
A pedal can sound good while still feeling like a pedal has been placed between you and your amplifier.
The Cornerstone felt much more integrated into the rig.
It Also Works With the BOSS Katana
I kept the same basic Cornerstone settings and moved over to the BOSS Katana.
Again, the pedal worked surprisingly well.
This is where I started thinking of the Cornerstone as much more than just a distortion pedal.
Yes, you can turn up the gain and use it for proper rock drive sounds. That part is easy.
However, I probably enjoyed it just as much when I used less gain and treated it as something that made the clean amp sound more alive.
The Cornerstone seems to add some of that push and response you associate with an amplifier working harder.
And because the pedal remains dynamic, you can still control a lot of what happens with your hands.
That made the Katana considerably more enjoyable to play on the very clean setting I was using.
How the Cornerstone Handles Humbuckers
The last part of the test was a humbucker-equipped guitar.
As expected, the extra output pushed the Cornerstone harder and gave me thicker rock tones.
But this also demonstrated why the Mids control is such a useful feature.
The Revv Dynamis and BOSS Katana have quite different midrange characters. A pedal setting that works perfectly with one amp will not automatically sit in exactly the right place with another.
With the humbucker guitar and the Katana, I found myself increasing the Mids control slightly.
That was enough to get the sound where I wanted it.
It is a simple control, but it makes the Cornerstone much easier to adapt to different rigs.
Instead of having one fixed “British pedal” midrange and hoping it works with everything, you can actually fine-tune where the pedal sits.
The Bright switch does something similar at the top end.
If you move from bright single coils to darker humbuckers, or between amplifiers with very different high-frequency responses, having that extra adjustment makes sense.
The Dynamics Are the Best Part
There are plenty of good British-style overdrive pedals.
That alone is not enough to make one interesting anymore.
What keeps bringing me back to the Diamond Cornerstone is the dynamic range.
Some drive pedals immediately make the guitar feel narrower. You might like the distortion sound, but you also notice that some of the response and width of your amp disappears as soon as the pedal is switched on.
I have never really enjoyed that feeling.
With the Cornerstone, I had almost the opposite reaction.
The sound seemed to become bigger.
More importantly, it still felt connected to the amplifier behind it.
If I picked softly, the sound responded. If I dug in, it pushed harder. Different guitars still sounded noticeably different from each other.
That is exactly what I want from this type of overdrive.
I do not necessarily want the pedal to become the entire sound.
I want it to make the sound I already have more exciting.
The Cornerstone does that extremely well.
Is the Diamond Cornerstone a Plexi-Style Pedal?
I would definitely put the Cornerstone somewhere in the British, Plexi-inspired amp-in-a-box world.
However, I would not get too obsessed with trying to decide which exact vintage amplifier it supposedly recreates.
For me, the more important thing is how the pedal behaves.
It has the crunchy midrange, drive texture and response I associate with a pushed British amp. The dual gain controls also let you move between different versions of that basic character.
At lower settings, you can get open broken-up tones.
Increase the gain and you move into classic rock territory.
Push things further and there is enough saturation for bigger lead and rhythm sounds.
But throughout that range, the pedal maintains a surprising amount of clarity and dynamic response.
That is what makes it interesting.
Who Is the Diamond Cornerstone For?
The Diamond Cornerstone makes the most sense for players who want classic British drive sounds without completely replacing the personality of their existing amp.
If you want a heavily compressed distortion pedal that creates almost the entire tone by itself, there are probably better options.
The Cornerstone is more interesting if you care about dynamics.
It also makes sense if you use several guitars.
The Gain 1 and Gain 2 controls let you change the drive character, while the Mids control and Bright switch make it easier to compensate for different pickups and amplifiers.
That could make the Cornerstone particularly useful in a studio.
You can move from a Strat to a Tele to humbuckers without feeling like you need a completely different overdrive pedal every time.
It also works with both traditional tube amps and something like the BOSS Katana, which makes it more flexible than its vintage British character might suggest.
Diamond Cornerstone Review: Is It Still Worth Buying?
Yes, with one obvious complication.
The Diamond Cornerstone is discontinued, so buying one today probably means searching the used market.
I would not recommend paying some ridiculous collector price for it just because it is no longer made. There are plenty of great overdrive pedals available.
However, if you find a Cornerstone for a sensible price, I think it is absolutely still worth considering.
The interactive dual gain controls remain clever. The Mids and Bright controls make the pedal easy to adapt to different rigs. And most importantly, the dynamic response is excellent.
Pedal technology has certainly not reached a point where those qualities have suddenly stopped mattering.
Final Thoughts
Having played quite a few British and Plexi-style drive pedals, the Diamond Cornerstone might be one of my favourites.
And the reason is not that it has dramatically more gain or some magical EQ curve.
It is the way the pedal feels.
The Cornerstone does not immediately squash the sound or make my amp feel smaller. Instead, it can add gain, size and aggression while still retaining the character of the guitar and amplifier underneath it.
The dual gain controls also make much more sense once you actually start playing with them. Being able to change the relationship between the more preamp-like Gain 1 and the more power-amp-like Gain 2 gives the pedal a lot of range without requiring a complicated control layout.
Then you have the Mids control and Bright switch, which make adapting the pedal to different guitars and amplifiers easy.
You can use the Cornerstone as a proper rock overdrive.
You can use it for lower-gain crunch.
Or you can turn the gain down and simply use it to make a clean amp feel more lively and responsive.
That versatility is great.
But the dynamics are what make the Diamond Cornerstone special to me.
It feels less like switching on a distortion pedal and more like asking the amp to work a little harder.
And that is exactly what I want from a good British-style overdrive.
You can check out the gear mentioned in this post through the affiliate links below. Using them does not cost you anything extra, but it helps support isthisgeargood.com and keeps the lights on around here.
Gear I Use: https://www.thomann.de/fi/thlpg_to75kzs7bv.html
Leave a Reply
You must be logged in to post a comment.