Sunday, March 20, 2022

Well, You Can't Win Them All!

Sometimes life slaps us in the face just to see if we're still paying attention. One such instance for myself was the other day when I was trying to put the finishing touches on what I felt was my most ambitious guitar pedal build yet. This pedal was meant to be my foray into JFETs, but it didn't go as planned. I was already anxious about the project because I finished the circuit board back in October of 2021, but I didn't have the JFETs or the enclosure to put it into until more recently.

The project in question is a RunOff Groove Umble. I was instantly intrigued by how good this pedal sounded in the demos I found online. The build seemed simple enough, but I was nervous about the need to manually bias the JFETs. To compound my anxiety about this build I used perfboard instead of stripboard, as I was running low on stripboard. I had made a few pedals using the perfboard and they turned out alright, so I figured I may as well, right? HA!

It will look pretty cool once it's done though, right?

I originally planned on this to be the first pedal I finished for the 2022 season, but instead I built two other pedals. Even though all this project needed was wired up and the JFETs biased, I was still putting it off until I felt I couldn't put it off anymore. Wiring didn't take as long as I had feared, which was nice, because I really do hate wiring guitar pedals. With everything setup it was time to put the board into the housing, bias the drains and bask in the glory of finally having built what I consider to be my most complex build so far. That's when things took their turn.

I cautiously plugged the pedal in, as I always expect something to blow up the first time I plug in one of my builds. Can you guess what happened next? Well, nothing exploded, so that was a plus. I was relieved to find that 9 volts was flowing into the pedal as it should and nothing was smoking, smoldering or exploded. Time to bias the drains. Right? Nope, what I had worried about the most became the issue I wished it wouldn't have.

I think my first problem was the layout I used calls for 100k, but I used 10k because that's all I had at the time, but that simply didn't work whatsoever. In an attempted Hail Mary I removed the 10ks and installed proper 100ks. Can you guess what happened next? Nine volts goes into the pedal, the 100k biasing pots turned all the way down only brought it down to 8.5 volts. Yep, something's fucky!

Handwriting FaIL too.

It was at this point I decided to activate Plan B, which was to cut a completely new board out of stripboard and attempt to build this pedal all over again. I've had to tear down pedals and rebuild them from scratch a few times, but I really didn't want to have to build this pedal more than once. For over an hour I sat there harvesting all the parts off the perfboard failure and testing them to make sure they were still within spec and could be reused for the rebuild. Everything checked out good enough, so I just bagged them up and decided to wait a few days before giving this project another try.

After a few days of rain the sun finally came back out, so I decided it was now or never. I rebuilt the whole pedal and set everything up to bias the JFETs. Well, it turns out I am an idiot and didn't know the JFETs need to be in place to be biased. See, I assumed I could bias the sockets I installed to accept the JFETs prior to putting them into place. NOPE! That's not how that works. Lesson learned, we're moving on. The reason I used sockets is because I had to build my own J201s from the surface mount size and convert them to through-hole. Also this gives me the option to change what's in there right now for TO-92 version J201s in the future.

While testing the pedal it sounds very thin and weak until the volume was cranked all the way up, but then it started screaming because it was cranked all the way up. I've had the screaming issue with a few other pedals and I'll figure out a fix for this someday, just not today. The EQ section seems to work, it's just the bias is still off, even at the suggested 4.5v. I guess those are rookie numbers and I'm going to have to pump those numbers up. For now the pedal is what I would consider finished, even though it still needs some tweaks, which will hopefully bring it around to working properly. I have dubbed this pedal the Humble as this pedal has well and truly humbled me.

Update: 12, April 2022

After sitting on this pedal for a while I finally decided to tinker with the biasing and was able, rather quickly, to figure out which JFET was the offending party. To be honest all of the JFETs needed a little voltage adjustment, but I blame myself in building the adapters to make them through hole from SMD. I still want to track down genuine TO-92 formfacter J201s, but for now it's functioning. I'm not exactly sure this is how it should sound, but I managed to dial in a much better effect than it was the day I put it in the enclosure. Now that I'm confident with biasing JFETs I will continue to tweak this pedal and I may even attempt more JFET based projects.

Tuesday, March 15, 2022

Pedal Building: The Centaur Clone

My guitar pedal building season 2022 started Monday March the 14th. It was a blustery day and the shade of the back deck made it almost unbearable, but I knew I had to get started sometime. My first pedal build was the Klon Centaur clone kit that I had just gotten a few days prior. I put this one ahead of my other builds as I felt time was important. Should there be any parts missing or issues arise with this pedal I would need to contact the seller as soon as possible. At present everything seems to be fine, for the most part.

My workspace on the back deck.

I started off as I always do; lowest components first and work upwards from there. I tested one of each component to make sure they were all labelled correctly. Can't be too careful! Everything was well marked on the main board, with the exception of one of the 100k resistors and the 821pf capacitor being a bit off, but I knew where they went after everything else was soldered up and they were the only parts left and their slightly misaligned places were left empty.

Stage 1

Stage 2

Stage 3

Once the main board was populated it was time to put everything into the housing and do some wiring. Wiring has to be my least favorite part of pedal building, but it has to be done. My distain for wiring was compounded by the fact the provided instructions are extremely vague on what wire goes where. I've wired up enough pedals to know how to wire up the input, output and DC jacks, but where on the board they go is the main mystery here. After doing some research I felt I had a good enough grasp on what went where and I went to work soldering it all up.

Stage 4

The problem is, I was wrong. Even after watching a few videos of people building it from start to finish and reading through some tutorials I still managed to get the output jack wired wrong. Once that was all squared away I had built a really nice pedal. Now, the elephant in the room is that this is a clone of an extremely well known and exceedingly sought after pedal that costs more than a decent used vehicle. That's exactly why I decided this was a project I was more than willing to tackle. I'll never own a real Centaur and even if this pedal doesn't replicate the tone exactly, what this pedal does still sounds pretty good to me. That means it's time for me to start my next project. Stay tuned!