Circuit Test Box

Let's be honest, there are certain projects or pieces of equipment that are the epitome of unsexy. They just aren't exciting. Why buy patch cables or a power supply when they cost more than that new, great overdrive you've been reading about? Well, the circuit test box is one of those projects. However, despite its lack of appeal, it really is an essential tool for making any DIY projects. I have had many times where I was certain I had the circuit all wired up right, put it in a box, and fired it up, only to find out that there was something wrong. Sometimes it was dumb, sometimes it was tricky. In all cases, a lot of the frustration could have been alleviated by building one of these guys. They also make evaluating breadboarded circuits a breeze.

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I have actually done four versions of the test box to date. First, I got by with the version from tagboardeffects just fine for a few years, but as I started moving into stereo effects, and the mono out just didn't cut it anymore. Additionally, I found that a very annoying part of the process was having to continually strum the guitar, pick up the probe, and try to probe the signal before the chord died out. Really annoying. So, I also built a simple 555-based timer from this video and gave it a volume control and a switch. The end result is a great looking and working unit. The perf board layout for the circuitry is below, though there is a ton of offboard wiring. Make sure you pay attention to how it's all wired, and it will reward you well. 

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After using the version in the perf layout below for a while, I decided I needed something that would make it so that I didn't have to be constantly connected to my computer for monitoring the audio probe and test tone. I then designed a PCB-based version that had board mounted toggle switches and LED's, onboard tone generator and probe connections, and a preamp/cab sim/headphone amp. It also supports true stereo in out using a 4PDT toggle switch with Millenium Bypass 2 for LED indicator (since a 5PDT isn't common at all). This is the 1.0 revision of the Super Awesome Test Box 2000 (SATB2k).

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After using the 1.0 revision for a while, I noticed that it always puts the probe output on OUT L and the test tone only goes to the SL (send left, which goes to circuit input). This is fine for many people, but with true stereo effects, it can really be an issue. This led me to the 1.1 revision which has a stereo preamp/cab sim/headphone amp section for monitoring (complete with toggle switch for selecting mono or stereo monitoring) and it sends the probe output to both OUT L and OUT R while the test tone goes to both SL and SR (left and right circuit inputs).

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So there we have it. If you want to do the version with just the probe and test tone, use the perf board layout below. If you want to use the Stereo/Mono or Full Stereo versions, stay tuned. Lots of documentation happening for that. In the meantime, I do have some boards and kits on hand. Just contact me. If you have a PCB, kit, or fully assembled box, the Assembly and User's Guide is right here.