Buying electronic components online is always a dicey proposition. Some of the most reputable dealers are online, and I feature many of them on the sidebar. There are also some good sellers of vintage bits (many in Europe) on ebay. There are, of course, way too many scam artists and counterfeiters out there as well, so you have to be careful. I found a source for what was advertised as vintage (though the electrolytic capacitors appear to be modern axials - but that's actually the right choice anyway) parts to build an 18V Colorsound Overdriver / Power Booster pedal. It included 1/4 and 1/3 Watt carbon resistors, axial electrolytic capacitors, one ceramic capacitor, several "tropical fish" capacitors (which you've got to admit, are some of the coolest looking things ever!), and four transistors as well (though they're in modern form factors). I went ahead and took a chance and picked up a couple of them to see how they worked and compare the result to my recent Overdriver build.
Using vintage (or for that matter any non-standard) components on a modern PCB requires a bit of flexibility as they are typically larger than the space provided with wider lead spacing. For resistors, this just means angling them, which I've had to do on several builds. The axial capacitors were a little more tricky as I really didn't have room on the PCB to angle them, so I had to bring the negative lead over the top of the capacitor and down the side. I went ahead and added heat shrink insulation to the negative lead as the fit was a little tight. Where things got really hairy was with the tropical fish capacitors. These are fragile! I broke one trying to carefully adjust the leads to fit the PCB. If I ever do more of these, I'm going to have extra capacitors lying about. Fortunately I'd bought two sets of parts, but now I have to replace the missing capacitor from the second set.
The parts set also included a circuit diagram for the Power Booster itself (above), so I was able to cross reference the resistor and capacitors on that diagram with the circuit diagram in the AionFX build instructions. Of course, if you look at the diagram above and the PCB, you'll notice there are some extra parts including an eight-pin IC that look very modern sitting next to the vintage parts. As I mentioned earlier, the Power Booster runs at 18V, not 9V. This was originally done by putting two 9V batteries in series. The AionFX board simply adds an 18V charge pump to the circuit on board so the pedal can run on a conventional 9V power supply or battery.
I've highlighted the non-vintage portions of the circuit above. Most of what is highlighted is the 18V charge pump. There is also one modern metal film resistor (the pull down resistor) and the 100uF power supply filter capacitor in the bottom left-hand corner. As the sole function of this part of the circuit was to take my clean 9V power supply and boost it to a clean 18V power supply, I used all modern components.
Any time you're using older components, there is a larger risk that something can go wrong. I tested every part before I added it to the circuit board, and with the tropical fish capacitors, I double checked them on the board to make sure they hadn't been damaged during the soldering process. With everything checking out on board, I finished primary assembly and hooked it up to my tester. The LED lit up first time, so then I was off to the tone test.
I added it to the board and proceeded to play it against the Overdriver pedal. First, I'm going to say the tone is amazing. The volume knob gives you a very useful boost, and the treble and bass controls give you a lot of flexibility as well. More profound differences show up in the drive control. You seem to get a lot more distortion out of the Power Booster (if you want it) than out of the Overdriver. There could be a couple of reasons for this. First, the circuit is running at 18V which tends to be an advantage for boost circuits. AionFX even offers an 18V voltage doubler that is compatible with many of their pedals (for you literary types, that's foreshadowing). The transistor layout in my Power Booster clone is also different. I used Fairchild BC184 transistors for all stages of the Overdriver, but the first stage of my Power Booster build uses BC169 transistors. Unfortunately I didn't record the gain on any of the transistors used on either build - though I did check all of them on my Peak Atlas - largely to make sure I had the emitter, base, and collector correctly identified. I may have to build a few more of these using both vintage and modern components to really understand what benefits (if any) the vintage components are truly providing versus the simple change of voltage and transistor gain.
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| Original Gary Larson Far Side Comic from 1982 |
Unlike the Overdriver build, I decided to go with an original enclosure on this one - as honestly this is a pedal I could see myself selling a few of in the not so distant future. It pays homage to the original Power Booster enclosure, but the fonts, text, and name are all unique to this pedal. As to what a "thagomizer" is, it's the spikey end of the tail of a stegosaurus. Gary Larson coined the name in a 1982 Far Side comic, and the term has actually been unofficially adopted in the paleontology community since. I figured the name would work for a pedal that is supposed to give your tone a real whack!
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