Most developers use a simple breadboard (see picture) at some stage as they are working out a new electronic circuit design.
The trouble with using these for developing guitar effects is when it comes time to connect your input and output jacks and maybe you want to have a bypass switch so you can compare the dry guitar sound with the sound coming out of your brand new effect. Then there’s the need to wire up pots for the effect controls and perhaps you’ll need to swap them out to try different values. And what about toggle switches? Many effects have one or more toggle switches to select options such as tone shaping or extra gain or whatever.
There’s nothing more annoying and frustrating than the jack sockets falling off the breadboard every time you pick up the guitar to try out the new gizmo you’ve been working on or the pots disconnecting themselves when you try to turn a knob.
I finally gave in and, with a lot of those thoughts floating in my brain, the idea of a breadboard dedicated to the task of developing guitar effects began to emerge.
As you will know if you’ve spent any time reading this blog of mine, I enjoy finding ways to include some sort of microcontroller in my projects, usually an Arduino Nano because of its small size. The final push I needed to get the bits together for my new ‘super breadboard’ came when I found and bought an ‘Arduino Nano Development Board’ on eBay. This was a very good idea that I wish I had thought of myself!
It’s the large green pcb on the left in the photo below. It has a number of buttons and LEDs and a couple of trim pots prewired to connectors on the board. There’s also a LM7805 5V regulator if things need a bit more power than the Nano’s own 5V output can provide, for instance, to power up servos, up to 12 of which can be connected to the standard servo connectors in the middle of the board. The board’s designer, Mike Hawkins, also included provision for a 0.96″ OLED display and a small breadboard for any extra circuitry you might want for the digital side of things.
I found a suitable piece of MDF in my garage and gave it a couple of coats of white car primer before starting to figure out how to fit in everything that I wanted to include. I added a couple of the larger 830 tie point breadboards to the centre of the board and I wired up a sort of dummy stomp box in a Hammond 1590B enclosure which houses the In and Out jack sockets, a 3PDT bypass switch and ‘effect on’ LED plus some DC power jacks and a four-way terminal block on the top.
The + and – terminals take flying leads from the 9V supply to the power rails on the breadboards and the S and R terminals (S)end and (R)eturn the signal to the effect circuitry on the breadboards.
Just between the large breadboards and the in/out box is a small module that can boost the input voltage up to 45V. For circuits that require more than the 9V you get from a ‘standard’ stomp box BOSS-style PSU, this handy module can be set using the multi-turn trim pot to whatever voltage you need – I have mine set to put out +18V which is a common value in some circuits used to give them extra headroom.
This DC-DC boost/step-up converter module (£3 from Hobby Components part # HCMODU0091) is based on the XL Semi XL6009 DC-DC converter and is capable of boosting a wide range of input voltages up to a maximum of 45V. Its output can supply up to 2.5A out current (dependent on input voltage and operating environment) and has built in thermal limiting protection circuitry. An on-board multi-turn potentiometer allows for adjustment of the output voltage which can set anywhere from Vin up to its maximum output voltage.
Just above the stomp box is an FV-1 development board carrying a Spin Semiconductors SKRM module. This was the module that started it all off for me as it formed the heart of Piet Verbruggen’s, by now famous, eTap2HW project. That led eventually to the development of the Blue Nebula pedal.
The FV-1 is the DSP chip that makes all the ‘magic’ work in those and many other guitar effects and amplifiers.
Since the photo was taken I have completed the module by adding the 8-way rotary switch that selects one of the 8 effects that can be programmed into the EEPROM on the module, using a PICkit2 programmer that connects to the socket on the right-hand end of the small motherboard into which the SKRM module is plugged. This also holds the three pots that are used to adjust the effect parameters, just as the P1, P2 and P3 knobs do in the Blue Nebula.
The front panel
To be continued …