Good question: The Diamond Drive is much brighter, less Gainey sounding than the 69 Stones.
The architecture of the circuit is commonly used in many amp/tube sounding circuits. Catalinpedals comes to mind. These while similar in that manner do have several key differences that matter.
- Gain modification, how the Gain reacts when turning the Knobs which is done by Taper.
- Gain Value which is perfectly set for each circuits namesake.
- Equally important are different Coupling Caps allowing different frequencies through each circuit.
The 69 Stones Drive has more Gain and will get there much quicker and is darker sounding while the Diamond Drive holds onto the cleaner chimey tones you would find in a Vox.
Then of course playing them brings certain tones to mind which I hope is demonstrated in the demos.
That is about it. We offer two boards that have unique sounds despite the similar topology just like we have a Dr. Phybes and The Vibe. There are only four values which turn it from a Phaser into a Vibe.