I finished up a creation that I've wanted for a long while, but never could have done it without the amazingly generous nature of @Sushi Box FX . His DIY Space Heater board gave me the flexibility to make a lunchbox preamp/DI that not only works great, but exists in a form factor that makes it more practical to me than a standard pedal. When playing Double Bass, I really don't like using pedals. I don't like the cables and board on the ground where my end pin rests, and I've pulled pedals off the top of my amp when I just have a single one sitting up there. I know, I know... first world problems for sure. I almost bought a Sarno Black Box, but it doesn't have the DI option I wanted. So I cobbled this together and it works so nicely for me. I've used it on 6 or 7 gigs already and it does exactly what I need. Don't get me wrong... I also love my HW UA on electric bass and it's become an essential part of my tone for both fretted and fretless bass.
The details:
I took the DIY Space Heater PCB, and put an HPF filter in front of it. The HPF did two amazing things for me. First, it's an HPF (yay). Second, it gave me a buffer that helps with the high impedance of my Yamahiko pickup and feeds a signal into the Space Heater that is a more palatable 100 ohms on the output side. Plus, when I'm playing DB those are the only two things I ever really want in my signal chain. That Space Heater with a Psvane 12AT7 is just the most wonderful combination for Double Bass ever. Not really fuzz, not really tube compression, but something else entirely. It's intangibly perfect when my piezo runs through it.
(We're not gonna talk about how I accidentally swapped the position of the Level and Gain labels... I was holding the PCB upside down when creating the artwork and this is my only piece of waterslide decal paper... for Gods sake Jim I'm a musician not a graphic artist!).
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Everything is powered by a Mean Well RS-15-12 that gives me a steady 12v and 1.3 amps. This is especially great for me because everything else I use takes a standard IEC power cable. I always have 4 or 5 of them in the back of my car. I only have a single One Spot. As great as it is... my odds of forgetting that One Spot are extremely high. This helps significantly with that potential issue. I also chose to put a Lightning Boy transformer in there, because they're awesome. The toggle lets me flip a switch to determine if the XLR balanced out is run through the Space Heater, or bypassed and just run direct from the input signal of the bass and the HPF. The small button on the lower right is the true bypass for both XLR balanced out and the 1/4" output to the amp. The black knob is the HPF.
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The wiring could be a little cleaner, but this is the first time I've used silicon hookup wire and it was a little weird to work with. It is a little more squiggly (?) than the regular old hook up wire I'm used to... but I like it. If I ever build another I'll plan out some better runs and maybe incorporate some sort of loom or harness to clean things up. The other tiny PCB coming off the push button is an Uber relay switch from TH Custom. A super cool little true bypass that also has a momentary mute capability when switching off and on. It allowed me to use an illuminated LED ring momentary switch on the front panel that flush mounts. Oh the enclosure is a Hammond 513-0900 steel enclosure. Now that I've built it, I realize I could have gone a little smaller... but from an ergonomic standpoint this really does work out nicely. Plus adding that drawer pull to the top that I found in my parts bin really helps.