A few years back, I was meeting my friend Andrew for coffee and co-working at a downtown coffee shop. When I parked my car, I happened to catch an interesting sign on an unassuming little building. Intrigued, I wandered over and discovered that the proprietor made small, hand-built noise-making devices. We chatted a bit and I really wanted to take something home with me. He showed me Krankie, a manually cranked music box with a recording/playback capability. Additionally, you can alter the playback speed of the recording, providing hours of entertainment. The kids loved it, and we made a few music strips for it and mostly played around with its recording feature to record our voices. There is also an audio out feature, so I plugged it into my recording interface to see how it recorded. Unfortunately, the signal was way too loud and it clipped, no matter how low I put the preamp volume. So, I left it alone and thought I’d get around to it another day.
Fast forward to Feb 2021. I’d been recording more due to the pandemic keeping us at home, and I remembered that I was going to look into why Krankie’s output is so loud. So, I did a little of this and a little of that, but couldn’t tame Krankie’s levels. I even got on a chat with the creator via the web site and discussed some options. He hooked up a Krankie to his Focusrite Scarlett interface and was able to get a usable signal. He indicated that he needed to flip the “instrument” switch on that input to bring the level down. Ah, that was the problem. My interface has no such switch.
I assumed that the “instrument” switch was effectively an input pad. So, I googled up schematics for input pads and found that it’s basically a few resistors. I breadboarded the circuit and used trial and error to find the magic combination of values that would tame Krankie’s rage. I tested the circuit and then experimented a bit more. I discovered that the whole thing worked with a single resistor between tip and sleeve. I don’t think I quite understand why, but it saves some soldering. With this information, I thought I could simply use a TS to TS cable with the resistor soldered in on one end. I clipped the resistor to the contacts on one end of the cable and tried it out. No joy. Krankie was too loud again. Then, I recalled the creator mentioning that I needed to make sure the cable coming out of Krankie is stereo, not mono. so, I switched out the mono cable for a stereo one and it worked. I ventured a guess that the output was being sent out on both channels and perhaps tip and ring were shorted. A test with the mulitmeter confirmed this.
I had a working solution so I set about looking for an appropriate cable. I had just purchased a TRS insert cable (one TRS end to two TS ends). These were a little on the pricey side, so I didn’t want to buy another one. All the inexpensive ones were molded ends, so I wouldn’t be able to solder in my resistor. Then, I thought maybe a little junction box might be the better solution. they make very small stompbox enclosures, and I really just need 3 jacks. This way, I could use cables I already have and wouldn’t have a hacked cable lying around. I priced out the parts and building a single box was cheaper than buying a cable. But the enclosures came in packs of 2. That was fine, because I have been meaning to build a foot switch for my older daughter’s guitar amp.
I ordered the enclosures, but they shipped very slowly. They finally arrived late March and I couldn’t wait to get this box put together. I had originally wanted to put the 2 quarter-inch jacks on the same side, but because of the screw housing inside the enclosure, they wouldn’t fit. So, I decided to put them on opposite sides of the enclosure. I went ahead and drilled the holes and test fit the jacks. They barely cleared each other, and when I put cables into the jacks, the tips of the cables touched each other. What to do? Looking closely at the jack, there is a slightly larger ring around the threaded part of the jack. as seen below. If I could somehow drill part way through the existing hole with this slightly larger diameter, I’d gain a little space.
I was able to fit a stepped drill bit into the enclosure, then stick the end of the driver through the opposite hole to bore out the indentation. Whew!
I made putting the rest of the circuit together a lot harder than it should have been. I mounted the connectors, then soldered it together in-place. I should have soldered it outside the enclosure, then stuffed it all inside. Live and learn.
So, what’s next? Decorating the case, of course! I think we’ll go for a robot head theme, since it kind of already looks like a robot head. We’ll experiment with a few different things. I think we’ll go for a vinyl sticker first, then maybe try laser engraving. I definitely want to try giving it a brushed finish and some clear coat to give it some class.
I’d like to thank Richard at Brand New Noise for making Krankie, and for spending time with me to debug the situation. Without his help, I wouldn’t have figured this out.