Saturday, November 5, 2022

Guitar Pedal Building: Learning as We Go.

Three years into pedal building and I'm still learning the basics of assembly, modifying and troubleshooting. After each build I go through a process of comparing my build with the genuine version from as many possible sound examples as I can find online. Sometimes I'm fairly close, sometimes I'm really close, and other times I need to tear the whole thing down and rebuild it from the start. The other alternative is to accept the results, but make notes in my paperwork to fix it later.

The problems all started with a few pedals I've built using LM741 op amps that I bought from Amazon, whose notes say *checks paperwork* weak op amp, question mark. I've bought a lot of op amps from Amazon and initially it seemed to be good value for money. Sadly, heaps of op amps started to come in weak, fizzy and in the case of a pack of TL071s I bought a month ago, not working at all. This has taught me which sellers to purchase from and why you spend a little more on a trusted seller, rather than save with a questionable seller.

The main example is my Rata Blanca pedal; for those who do not speak Spanish it's a Rat clone. I know some people demand any Rat circuit to have a 308, some will even accept an OP07, but I was going super cheap and wanted to use the 741 stock that I had. Not yet knowing the ones I hadn't used yet were all poor quality, I was in for a very bad time. Initial testing was extremely frustrating as the pedal would squeal at any gain above 30% with a very faint hint of a hissy effect underneath. I checked for solder bridges, etc. and found absolutely nothing wrong with the circuit. After going back through my notes I started to put 2 and 2 together and got 741. I may not be good at math, but I can deduce that the 741s are the issue.

After ordering a new set of 741s from a reputable seller I was actually quite blown away and smitten by the circuit. It no longer squealed (as much), was a lot more dynamic, and the hissy mess was completely gone. Now, I'm admitting it's a 741 in a Rat circuit, so sure I may not be getting the whole Rat "thing", but simply going from a potentially fake 741 to what I assume is a genuine one really brought this pedal to life in a completely new way. Would I like a 308? Sure! Will I buy a 308? No. Even if I'm not getting the true Rat experience by using a 741 op amp, I'm still super impressed with the circuit as is. Maybe I'll build another and use a true Rat connoisseur approved op amp in that one. Maybe.

As I said earlier there are a handful of other pedals that have the shitty 741s in them, so I'll be doing surgery and swapping out the op amps soon. The most important lesson I've learned is quality parts are important, especially the op amps. As I move forward in my journey to build all the effect pedals I want I will implement all the lessons I'm learning along the way, and I'm sure there are still more lessons to be learned. I'm excited to get the 2023 season underway in a few months. I have five kits already setup for myself and some parts on order to complete them. Over the winter I'll find more ideas, I'm sure, but the 2023 season will be one of exploration in new territories with even more lessons to learn and mistakes to make. Let's just hope I don't do too much damage.


The three main pedals that had the faulty 741 chips in them were my Morley MOD D1B clone, my Crowther Hotcake clone and my MXR Distortion Plus clone. After a bit of fiddling about with each pedal I removed the op amp and put in sockets, which were later filled with better quality 741 chips. After some audio testing and comparison I can say the Morley and Crowther clones are both amazing circuits and I'm super happy with the results. The distortion plus however seems to still suffer from a bit of fizz. I've listened to it side by side, to the best of my ability, with youtube sound clips and it sounds similar, but not as close as the other two sound to their genuine counterparts.

I've learned two lessons from this little experiment, the first of which I acknowledged in the original writing of this entry which is do NOT cheap out on op amps, buy from reputable sellers. And two is do NOT solder an IC, including op amps, directly into the circuit. I had a terrible time getting my desoldering tool to remove them, but once all was said and done, sockets were installed and these circuits are now working to their full potential, with the exception of the distortion plus. I'll continue to troubleshoot the MXR Distortion Plus clone, as now the op amp is socketed and can be easily swapped. After realizing just how good 741 circuits can sound, I've got a few ideas floating around in my head. We'll just have to see if they fit into the 2023 build season.

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