NPD - DIY Germanium Fuzz Face (OC42)

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MrShake
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NPD - DIY Germanium Fuzz Face (OC42)

Post by MrShake » Thu Jun 02, 2022 5:12 am

Knocked another one out, this one was a struggle.

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I rigged up a germanium Fuzz Face board with trimpots, and when a pair of transistors showed up, I plopped 'em in to see where I stood. I could get sound, but real weird and I simply couldn't get the voltage at Q2's collector below, like, 8.5. Clearly, something was wrong. I checked my wiring and layout (a verified GGG-based vero layout). I built a second board. Same layout blueprint, new soldering iron, working exceptionally carefully. Same result. Unable to get the collectors anywhere near acceptable. Since it was my only set of Ge transistors, it was hard to determine where the fault was.

Okay, break time. Got a breadboard, worked for two hours following Small Bear and Beavis Audio's Si Fuzz Face breadboard tutorials. Nothing. Okay, go to bed, try again tomorrow. Fresh components and a fresh breadboard.

Worked immediately.

Seriously, I did both tutorials TWICE that first night and nothing. And I kinda understand the schematic and stuff, it wasn't just paint by numbers! I did find what I believe to be an error in the BA fuzz pot hookup (it was sweeping backwards for me), but that could very well be on my inexperience. I know it's a novice that blames the tools, and I'm a novice, but something wasn't adding up. I'll have to check it's continuity later.

So, then I took the plunge. I swapped out the transistors for my Ge pair, flipped the polarity of the two electrolytic caps, and swapped where the battery leads connected.

And it worked! PNP germanium goodness!

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So, inspired, I went back to the box. This time, I backtracked. I snipped out everything but the bypass wiring (that worked fine) and started fresh. This time, I built from the SILICON fuzz face layout sheet I'd had success with twice recently. But I was very mindful to reverse and double check the electrolytics and +/- rails. Fresh wiring to snipped and cleaned pot terminals, and no LED or DC jack to worry about, so that simplified things. I held my breath and hoped for no magic smoke.

And it worked. Sounded pretty good. Got the voltages to -0.5/-4.5 on my multimeter (though, side note, why does GGG suggest (-)1.5 for Q1? That seems really high...) and then it sounded GREAT. Spent a while just playing big saturated "Echoes" and shoegaze type stuff until I realized it was 11:30 at night.

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Went back to it this morning and checked the bias after a big weather drop overnight and still measured around the same... within .03, so I'm willing to let it be for now. Reading up on the transistors (assuming they're not fakes, which I don't think they are), they're late-'65/early '66 UK military spec OC42s. So, period appropriate, if not the vaunted NKTs or AC128s.

As for the sound, I really like it. I had a big red germanium one in the mid-'00s, but my rig wasn't right for it and I was too inexperienced to wield it, so it's hard to compare.

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I've got another set of lower gain GT308V transistors coming from a seemingly reputable seller, so I'm probably gonna build one more germanium FF, from scratch, maybe with a few more bells and whistles, put the best transistors in the best build, maybe leave the "spare" at the practice space for full volume stuff. Time to flex elsewhere, but not too far. Maybe it's time for the Colorsound/Vox builds. I've got some "tested but no values listed" Ge's coming too, so maybe it's time to get around to a germanium Fuzzrite too.

Even the failures on this ones were lessons, though. What size trimpots to use, how to debug, building techniques and mistakes, and even learning when to scrap it and start over. And worth the time and work for a killer fuzz pedal at the cost of a few clipped boards' worth of secondary components (i.e. not transistors).

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Now that these two can keep each other company, maybe I can figure out why I can't get my Hofner Buzztone up and running.

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