So based on your interest, I’ve decided to document the development process for a new pedal in the Rare Buzz lineup. To be clear (and this is as much for me as it is for you), this pedal is a ways out as it pushes my skillset further than any other I have ever attempted. It has a lot of firsts – the first stereo pedal in the RBFx lineup, the first pedal with digital control developed in house (previous designs used ready-made solutions), and the first to feature four-layer PCB design. This is an idea that I’ve had in my noggin since I started Rare Buzz, and finally feel confident enough to dive in. While I won’t let on what the effect will be called or what it will eventually do, I’ll discuss some of the development steps along the way. For the sake of reference, let’s call this pedal Project Middlemarch.
The first development challenge I worked through is the switching. I wanted to have the pedal handle any combination of mono and stereo at the input and output of the pedal, and I wanted to have it do this automatically on the daughterboard without the need for digital control. All of the CMOS switching is controlled by introducing or removing patch cables.
- If only one input cable is inserted, the pedal is mono at the input but can be stereo at the output.
- If a second cable is detected, the pedal will automatically change the signal routing to add the second input.
- If only one output cable is inserted, the two signal paths are summed and fed to the mono output.
- If a second cable is detected, each channel will be fed to its own output.
One of my goals (which created its own challenges) is to preserve existing stereo signals. If the two inputs are different, the two outputs will preserve that difference. By this I mean that the signal paths are never summed and split at any point in the pedal, and this “true stereo” must be preserved during the switching.
Speaking of “true” catchphrases… this pedal is not true bypass. It is buffered at the input and in the case of the mono output scenario, the summing amplifier is also always in the signal path regardless of bypass status. There are a variety of active and passive components throughout the switching, most notably CMOS switches. For most players, this should not be an issue. However, the limits of the system are roughly +/-4.5V peak to peak, so guitars with extreme outputs (I’m looking at you, Electrofoods) or previous high gain effects may introduce clipping, even in bypass mode. We plan to test this pedal at both 9 and 18V, and running higher voltages will increase the headroom accordingly.
Some neat side effects of this design – this pedal can either start or end a “stereo” chain. It can be used to sum two signal paths, even in bypass mode (although the two will be fixed at a 1:1 ratio), or to split a single signal path into two. Just this circuit segment, which will live as a daughter board holding the four audio jacks, was a challenge. Fortunately we will be able to function test it without the rest of the circuit.
More to come!