DIY Mixer and Effects for my Korg Volcas

I have been playing around with my Korg Volcas for a while now and I think they are really great. I thoroughly enjoy the immediate, “hands-on” music making experience I get from a small table-top setup.

I still use Ableton Live for mixing and effects though, which is less than ideal. What I really want is to bypass the computer all together – no DAW, only “real”, tactile gear. I see a lot of people on YouTube using small 4 way mono mixers, perhaps with a stomp box or two, but I find that approach a bit too simplistic for my needs. With only a few sound sources to work with I think it is really important to have something interesting going on in the stereo field, at least for the type of “down tempo” music that I like to make. I also need a good selection of delay, reverb and chorus type effects to create ambience and interesting textures.

I have been looking at the Eventide and Strymon guitar pedals which sound fantastic and would probably work great for me. Unfortunately they are also pretty expensive, and I have not been able to find a small form factor stereo mixer that suits my needs.

So, I started looking around for schematics online, thinking that I might build this stuff myself. The mixer is pretty straight forward, since what I want is really just 5-6 stereo channels with volume controls, a master volume control and nothing else. There are also a ton of DIY guitar pedal designs out there which could be adapted for my needs – this will require a bit of work though. Guitar pedals tend to work best on stuff that occupy the mid-range frequencies (such as… guitars) and almost all the DIY designs out there are mono only. Being powered by 9V DC most guitar pedals handle -10 dBv signals just fine (such as those from the Volcas) but impedance can be an issue, especially on the outputs.

Some of the more interesting and best sounding guitar pedal designs I have found are based on old school analog “brigade bucket delays” commonly referred to as BBDs. Most of these chips are out of production and horribly expensive but I found one company that still manufacture BBD chips and sell them at reasonable prices. I have done the math and figure I should be able to make at least 3-4 true analog stereo reverb/delay/chorus type effects for the price of a single Eventide/Strymon box. Plus I get to build them myself, which is fun, interesting and infinitely more satisfying than just forking over your hard earned cash to buy the same stuff as everyone else.

I have already done some work on the mixer and a couple of effects and will be posting about this soon, so stay tuned!

DIY Breakout Boards for Prototyping

I have been prototyping a drum machine on breadboards lately and found it difficult to make some components sit well in the boards, especially potentiometers and jack sockets.

Although I had carefully selected components that would fit in a breadboard, I was experiencing annoying issues with unreliable connections. I even had components falling out of the boards when I was moving them around (I am the proud father of a very curious 2-year old boy and need to store my prototypes on a high shelf when I’m not working on them).

I decided to solve this problem once and for all and spent an evening designing and building a couple of simple breakout boards for my project, using Olivier Gillet’s breadboard friends as inspiration.

Prototyping breakout boards

The breakout boards work just as I had hoped. They sit really tight on top of the breadboards and the connections are 100% reliable.

I also picked up on Olivier’s idea of using jumpers to set default connections – e.g. connecting the sleeve of the jack socket to ground and bridging tip and ring so that only a single wire is needed to incorporate the socket in a circuit in “mono mode”. This approach not only saves time but also reduces the number of wires in my prototype, making it easier to work with.

I really recommend this approach, even for fairly simple prototypes: What worth doing is usually worth doing well – especially in engineering projects.

You could use strip board for your own designs as long as the power rails on your breadboard match “standard” dimensions – this is not the case with all boards. If you enjoy etching your own circuit boards like I do, that’s obviously the way to go – you can grab my Eagle files on GitHub and use them as a starting point for your own designs.