Blog

yo....

ok so i know i left off the last post all like "ohh im not gonna take months to write about the next module once it's done" and then proceeded to do. exactly the same thing again. but theres a good(?) reason this time, and its that i was doing a bunch of work on the site that i wanted finished before i made this post because it included some stuff that would make posting a bit easier. ok? more on that later tho cos first i gotta talk about the new module. ok????

The Module Known Only as "Sir"

well, here it is. a module i've been wanting to make ever since i finished my first one. it's a distortion module based on the schematics for marshall's "the guvnor" pedal posted on electrosmash (rip ;_;7). i saw this article back in 2023 and the first thought i had was "making a guvnor clone and calling it "the module known only as sir" would be a pretty good bit", but back then i literally only had a delay module (and i hadn't even finished that yet) so it went in the ideas hole for years. but recently i'd been wanting something to rough up my sound a bit and here we are i guess. a stupid joke 3 years in the making.

designing this one was actually pretty interesting. i started out with the schematic i mentioned, stripped out the loop jack and bypass since they're not super relevant for a synth module, then started adapting what was left to work with eurorack power and signal levels. i ended up smushing the gain sections of the input and clipping stages together to create a single gain/attenuation stage, which only goes up to 2x (6db?¹) since eurorack signals are strong enough already that the original circuit's combined amplification of around 3220x (or ~70db, but that sounds much less scary) would be comical levels of overkill. this left me with a free op amp, which i used in the output stage to make up the voltage lost to the clipping diodes. this all meant throwing out the filters present in the original design, but i ended up trying to recreate them as closely as possble in the new gain and level circuitry. although, while i was breadboarding it i did try dropping the initial high pass filter and it made the sound wayyyy more yucky (positive) so, i miiiight add a switch to turn that one on or off for future revisions....

after that i added a tone bypass, and then set about figuring out how much i needed to amplify the output to get back up to eurorack levels, which turned out to be a whole ordeal.... it's simple enough with the bypass on, a gain of ~2.75x brings it up to ~10v p2p no problem, but when the tone bypass is disabled the signal level is all over the place depending on how the bass/mid/treble pots are set. i experimented a bit with adding a trim pot for adjusting the max amplification which at least helps with getting it to a value that's kind of ok in most cases, but eventually i gave up and went searching for a clipping indicator circuit instead so i could at least see when i needed to turn it down to avoid frying anything. eventually i settled on this one that's apparently adapted from an old electronics magazine from the 70s? it took a lot of messing with resistor values to make it work right in this context, but it does the job and more flashing lights is always a plus. obviously i could've built a simpler indicator using another op amp instead, but for some reason i'd decided i really wanted to stick to just the single tl072 for this... not really sure why i did that, but i learned some stuff about transistor buffers so i guess it worked out in the end??

as far as putting it all together went, well.... initially it was looking really clean! this was the first module panel i drilled that didn't require filing any of the holes into alignment afterwards, which i guess means my freehand drilling skills are improving? although i still wanna get a drill press eventually. and then the panel wiring, i got that all lookin real nice in there..... but then i realised i'd i put the bass and treble pots for the tone control in backwards. and also wired the bass pot backwards. so from there it kinda just went completely tits up. there's so many components soldered directly to the back of the controls that i didn't wanna have to redo and in my stubbornness i tried to move as few things as possible, which resulted in the foul mess u can see in the pics. it works, but.... i should prooooobably rewire it at some point for the sake of reliability. i really don't trust some of those connections.

anyway. i'm really happy with the resulting sound, although like i said i do sometimes wish i'd left that initial high pass filter out. it's also, a bit wide at 10hp... i don't have much space left in my rack now and don't reeeeeally have anywhere appropriate for sawing wood to build another, so i've been trying hard to keep my modules small so i can fit the last few things i want into this one. and on that note....

i'll small my module

look familiar? it's the "mystery vca"² with a fresh coat of, panel. back when i made it i had plenty of space free so i didn't think too hard on giving it a full 8hp, but to fit everything i want in here i needed an extra 2hp, so i smalled it. rewiring this thing was an absolute trainwreck, but it's somehow still working, and since i'm a little low on hookup wire i don't really feel like i wanna bother rewiring the whole thing right now. maybe i'll take a look at it when i finally clean up the distortion module wiring....

what was that about site updates?

oh right yeah! so the big thing i was working on that held everything up was, i've been writing an mdex plugin that'll convert multiple consecutive image embeds into an "imageset", which i guess is the name i've given to those collections of side-by-side images in my blog posts. i write all my blog posts out in markdown, but until now if i wanted to put an "imageset" in a post i'd been doing it by copying and pasting a big chunk of html with inline styles from a previous post, then editing all the image urls and descriptions. which was a huge pain in the tits!! now i wrote this plugin tho, i don't have to do that no more, plus i've also written another plugin that lets me do audio embeds. it uses the same approach as gitlab does (ie. "just look at the file extension in an image embed and figure it out"), but since the only post i've written that includes audio embeds has them side by side, i'll need to integrate that into the imagesets plugin before i use it. and i'm kind of sick of writing plugins rn. soooo......

as a bonus, since i was already rummaging around in the guts of the cool goth zone, i did a few bits of cleanup around the site as well. off the top of my head the main things i fixed are the menu going off screen on mobile (still not sure when that broke) and the rss feed being invalid due to an ampersand that wasn't getting escaped properly³, but there's probably other stuff i've forgotten too. i also updated the about page since the pronoun order has been out of date for most of a year, and since i'm trying out a new name rn. u know how it is.⁴ oh and as usual, i've updated the synth page. the schematics etc for the new module are up on the repo too, but that's not on my site so who cares. but u can look at it or dont if u want. its there either way.

ok i'm done typing. im not gonna promise there'll be less of a gap between this post and the next but. here's hoping. for now tho? i'm going back to fucking around with arduinos and playing simcity 4....

see u in the next!

– fray