There are a variety of capacitors made from different materials from different manufacturers and there are even more opinions about which ones are the best. Over the years I've used different types of capacitors in modifications and instrument builds but it was always difficult to determine which ones sounded better than others. I had thought about different ways to sample capacitors but never set aside time to plan a way to do it. Once I started to work on tube amps it became fairly obvious one capacitor might sound better than another even if they had the same value. In an effort to hear differences I first sought out videos on YouTube. Kudos to the people taking the time to solder in different capacitors and make some pretty interesting videos. To learn a little bit about tone controls in an electric guitar check out a short article on my website here.
In one particular "Trade Secrets" video from Stew Mac, they had a simple rotary switch setup in the spirit of a Gibson Varitone that made it quick and easy to hear different capacitors so the customer could choose what they like the best. It was a great idea that lead me to go through my parts to see how many brands of capacitors I already had in stock. It turned out there were way more than a Varitone rotary switch could offer so it was clear a new project was just taking root.
At this point I knew I'd have to spend some time looking for a different rotary switch but before I did, it seemed to make sense to consider what other parts I might need and determine what exactly was I hoping to achieve with the final product.
- A way to quickly switch between different brands of capacitors
- Compare .022uf capacitors to .047uf capacitors (matching brands)
- Plug in a guitar with single coils or humbucking pickups
- Reference the resistance of the tone control
Whether it was over-thinking a simple thing or good idea in the works I wasn't sure, but I did know it was time to work on a drawing. It wasn't going to be an elaborate electrical design but it would require time to build not to mention some expense. I wanted to have a solid plan before ever ordering the parts and it wasn't something I wanted to do more than once.
I already had a Hammond enclosure which turned out to be too small for a different project. Rather than return it I'd try to put it to use and that would establish the space I had to work with so I began working on the drawing using a small dry erase board. There would be two rotary switches (one for each value of capacitors), a concentric potentiometer (250K/500K resistances), two mini switches (resistance selector, capacitor value selector) and two panel jacks (input and output). Each capacitor would need to be grounded so I could either use terminal strips or simple buss wire. In early planning the terminal strips would be easier to modify after the fact but buss wire would be almost certainly save space and offer greater versatility during the build. After briefly looking for knobs for a concentric potentiometer it occurred to me it would be possible to reference the resistance of the concentric pot with a multi-meter instead of relying on numbers on a knob and fortunately I also had these in stock. Either way, once it was built I could simply plug a meter in and get the actual resistance present in the tone circuit.
Once it seemed the idea was pretty solid and the initial drawing was complete it was just a matter of waiting on the parts t0 figure out the actual layout before drilling any holes in the enclosure.