How to convert a stompbox into a Eurorack module

In this episode, we convert a DIY guitar pedal into a Eurorack module. First, I explain how we're going to do it. Then, we make the conversion. Finally, we hook everything up and play some drum sounds through it to hear how it sounds.
0:38 - The plan
4:49 - The build
8:01 - Hear it in action
Join the discussion:
/ leomakesstuff
When not making videos I run Strange Science Instruments,
a modular synth company based in Sweden & California:
www.strangesci.com
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www.patreon.com/leomakes

[@dimitris470]

The lm7809 family of chips and their similars are greatly improved with some capacitance at the input and at the output to run more stable and improve transient response. Check the datasheet for recommended parts and values

[@channelite]

I've been wanting to learn how to make 9v to 12v eurorack. I started soldering noise making kits that run on 9v and it will be much better to have them in a eurorack case. Thanks for this video.

[@tomvice]

Thanks for the kick+snare bus through rat trick🔥 I’ll be using it in my dumbed down version with a daw and prebought amplifying and level matching gear

[@iiWNMii]

Awesome safety advice on airborne particles.

[@howardhurtt6612]

I'd like to see how you did your fume extractor.

[@maxmatson1578]

The background music during the Montage was pretty badass!🎹 rivet heads for life!!¡!🎹🎥🎧💫😵💀👌

[@robbo916]

Great channel!

[@josuezacahua8331]

Thank you very much, now I can convert an eurorack to a guitar effect, cheers

[@almohadillaseisefes]

tnx for sharing!

[@mookie714]

I was thinking about doing this with a boss MT-2 metalzone pedal, but now that I see how it's done I'm going to give it a go.

[@axeman2638]

You might actually be able to do something useful with it as a rack module, it's useless for guitars.

[@HeavyListeningMusic]

It's far from useless with guitars. Check out Ola Englund's video where he runs it straight into a poweramp instead of a preamp.

[@electricarchaic]

Thank you! I know I'll need this info some day soon :)

[@masterluu8]

I don't know what that RAT is doing with the 9V you feed it, I saw a couple of caps on there, but in general it's good practice to add a couple of filter caps on the input and output lines of a voltage regulator. Just so you have a very clean 9V signal that you feed into your equipment.

[@samharding8201]

Just picked up a RAT clone kit, going to build it straight into a module. Thanks for much for the helpful video!

[@LeoMakes]

You bet! Good luck with your build!

[@scottharris7222]

Very good video..I think a few of us would like a couple of shots of how you mounted your board onto the blank panel. Cool project for sure! Subscribed. By the way this came across on my feed as recommended so the algorithm for youtube seems to be working for you.

[@_functionless]

Super love your channel bro caught me by surprise

[@RyanHarlin]

Pilot holes to stop bit-wandering! Duh... how have I spent all this time trying to put down masking tape to just create a little friction but then STILL using big bits that do indeed wander!? Great tip - among all the other good tips. :)

[@LeoMakes]

Thanks Ryan. I actually learned this tip from a woodworking channel on KZbin but it turns out it works well on metalworking too!

[@electrosquish]

@@LeoMakes One step further is to use a center punch first then pilot. Once you start packing in jacks for CV control and switches for all the crazy RAT circuit bends those holes will get close. Better that than more HP anyway.

[@chodnejabko3553]

If you bother with regulating voltage, especially for fuzz & overdrives, it is a common practiice to run them off different voltages for different tone (f.ex tube screamer) so it is better to use a variable voltage reg. like LM317 & a knob for voltage regulation from, 5v to 18v. I was really hoping you'd be going over schematic changes to convert circuit from single supply to split supply, because split supply is better for op-amps, gives them better characteristics.

[@MichaelScottPerkins]

Awesome video! You mention in the beginning that you'd like to mount the PCB "sideways" rather than flat against the panel. During the fast fwd build shot, however, I can see that you opted to fix it flat to the panel. The video moves too fast however, so I cannot see how you mount the PCB to the panel. Do you drill a hole through the panel so you can attach it with one or more turrets?

[@MaxedMusicArts]

What would you have to do to make the distortion and filter cv-able ?

[@valdiorn]

btw most pedals will run absolutely fine on 12v - a Rat definitely will work fine on 12v :) Some pedals might have slight changes in sonic characteristics due to bias changes, but generally op-amp and diode clipping pedals, like the Rat, will not be affected at all.

[@LeoMakes]

You’re right on all counts! I discovered this about the Rat (and many other diode clipping based pedals) after posting this video but I left the video up as the concept can still useful for some viewers. Thanks for watching and your insightful comment!

[@92JelaniMusic]

Cool video, can you add CV next? Adding CV is 500x more useful than the form factor and 99% of pedals lack this.

[@MDJ5]

interrupt the pin of the potentiometer that is neither the ground nor the wiper with a switching jack for a quick and dirty CV and the knob will now also act as an attentuator for your incoming CV signal

[@Mike-gy2xd]

Is there any impact on signal level when going back into the 12V environment?

[@Jeremysfx]

great video and nice detailed instructions with tips you don't normally get. I really thought you would put some CV control in there. That is actually what I am most interested in. Any chance you know how to do this and are willing to do a video? That would be most excellent!

[@LeoMakes]

CV control is a great idea and one that I’ve been thinking about as well. I’d love to do this at some point but I’ve got some other videos in the pipeline for now so it may take a while to get back to this. Thanks for watching!

[@mackk123]

Gonna turn all my pedals into a 19" rackmount now.

[@drewmendez8293]

Awesome! Curious though, how would one go about adding attenuators + modulation inputs on the three parameters?

[@els1f]

The easiest way would be to use Vactrols (a light dependent resistor and an led sealed together). You ESSENTIALLY can replace them with potentiometers, but nothing's ever that easy lol 😋 The resistance in the vactrol is almost certainly not the same, but it's still fun. Look up the "Vac pak" by Synthrotek and start there. There are other more accurate ways, but they require a lot more fiddling, math and parts.

[@paulbergel9191]

Excellent video! I stumbled on your feed today and just finished watching all your videos! I may have missed it: what ended up being your solution for mounting the pcb perpendicular to the panel?

[@LeoMakes]

Thanks for watching, Paul! I tried test-gluing the PCB to the panel off camera but it wasn't working well at all, so I just ended up bolting the PCB to the panel with the hex nut around the switch. That happens around 7:08 in the video. It's not the most robust solution but it still works fine after 2 months.

[@ryanpwm]

How do you bypass where the power button is supposed to be wired. I have a turbo rat that I've modded to go an a panel.. FIY cutting the actual rat board and jumping wires actually fits on a panel just fine... only I did not read how the stomp pedal was wired correctly and have no sound on mine. Just the power light and nothing else. So I'm close... Just wondered how you have the pedal go while skipping the 3x3 matrix of the stomp pedal.

[@jamesnolan1270]

Great video Leo! I've a noobie question. You used the +12v supply from the doepfer power bus to power this module. Could you use the -12v to power a another stompbox module and get the 2 powered off of the one socket?

[@LeoMakes]

No, using the -12V would not be a good idea but if all your stompboxes use the same voltage (like 9V) and the Doepfer's wall wart power supply provides enough amps of current, then you should be able to power multiple stompboxes with one output. I wouldn't power too many stompboxes, though, since the voltage regulator is going to get hot as you pull more and more current through it. I didn't bother putting a heatsink on mine in the video since I only had one stompbox to power but you may need one if you're powering lots of things. Hope this helps and good luck!

[@neuesmusiker]

This video is awesome! Kinda curious though about lack of spdt switch in the construction the euro module. Does the lack of a switch in a circuit design that originally has one create any issues. I'm way more of a modular guy, but I've built a pedal or two and the wiring of those switches can be kind of intense, so i'm wondering if not installing a switch could potentially cause problems. Cheers!

[@LeoMakes]

Hey Michael, I don't think the switch will have any effect on the sound. These SPDT switches can be a bit of a mystery and it always takes a minute to remember how they route signals, but all it does here is to either route input to the PCB (where the distortion happens) or connect the input straight to the output (i.e., a hard bypass). So skipping the switch and connecting jacks straight to the PCB's input and output shouldn't really have an effect on the sound.

[@piotr803]

I really enjoyed this episode. Great job! Since you're planning to have a dedicated box for guitar stompboxes, then you don't really need a eurorack power bus board, instead you could just use a regular 9V power adapter to power the small case you have there, no? In which case the exercise becomes really about re-mounting the guitar pedals in a eurorack like case for easy interfacing, etc. Or have I missed a major point? thanks again for the video:)

[@edenmeden]

It might be a dedicated case now, but if you were to do that you'd be left with a bunch of stompbox modules and a case that are rather bound to each other. This way leaves the option to mix in eurorack gear in any way you want, as it should be lol.

[@dachimp4879]

What’s the voltage regulator you used?

[@syntheffects]

Some people plug the Rat into a 12v adapter no problem. How do you go about doing it, -12v into -9v, ground to ground and +12v nowhere?

[@madmac66]

Very cool, now how to go the other way. I want to put a vcf into a stomp pedal

[@graysonschiller3288]

link to the IC chip used?

[@ChurroLightyear]

Anyone got a way to make the knobs also take cv in or where I should look. Is there a way to use I dunno transistor gates to control the resistance from the pots

[@256k_]

I have a cheap amazon bought digital reverb pedal that i converted to euro module but the audio out is line level, how can i find the raw output? or do i have to add an opamp to add gain?

[@LeoMakes]

It's tough to know without studying the circuit but the most likely scenario is that you'll need to add gain. Or bring it into a module that has extra gain. Good luck with your mod!

[@TriangleWaveRecords]

Couldn't the rat circuit be powered by 12V also? I see that those IC chips can take a pretty wide voltage range.

[@Lalaland.001]

Also as far as my knowledge would go, would it not be safer to use a buck converter or step-down converter as far as my knowledge goes linear voltage converter produce a lot of heat when their input voltage is much higher then their needed supply voltage...wouldn't that thing overheat and drop out constantly....unless of course you would use a big heat sink...

[@TravellingSynths]

Man, this is super useful! I'm curious, did you convert more guitar effects to fill that case? I am now considering to convert my Robert Keeley compressor into a eurorack module.. Saying that I can't help but wondering if there's an "easy" way to add a side chaining jack.. 🤔 Would be pretty amazing!

[@ramongonzalez3000]

Hi, i starting this service. I will post it in ebay and reverb soom. You are very welcome in to send your stomps and we will return then to you converted in eurorack modules. We can do it based on your request.

[@TravellingSynths]

@@ramongonzalez3000 thanks, but I'm doing it for the learning as well. Will you share the knowledge, like Leo here?

[@ryanpwm]

How do you account for the eurorack signal being way hotter than a regular guitar line signal? Wouldn’t this drive the pedal too hard and need to be attenuated on the input and then raised again on the output?

[@LeoMakes]

The eurorack level is way hotter than guitar, so I found I had to keep the input gain knob closer to the bottom of its range otherwise the input was too hot. To avoid this, you can do is attenuate the signal on the modular side (before the pedal) using a simple passive attenuator. The output side seemed fine but if it were too low, you can gain it up. Hope this helps.

[@ryanpwm]

@@LeoMakes Ok makes sense. I settled on getting a stereo guitar module. Just makes things simpler and I don't have to use up a vca slot.

[@ericohman]

Where did you get the solder vaccuum flex tube?

[@LeoMakes]

It comes with the Metcal BVX-200 fume extractor. Quite good but probably overkill for a home lab.

[@snellcheeks]

Hi, great tutorial and an inspiration for "euroracking" stomp boxes! What type number of the regulator you used? Is it the LM7809? I see it's quite hard to get it nowadays, but maybe i'm looking at the wrong things...

[@LeoMakes]

Yes, it's a LM7809. The last two digits are the output voltage (9V in this case). Just FYI: I've heard that many stompboxes can take a pretty wide range of input voltage so if you can't find a 9V, you might be able to use a 5V or something else. Of course, you should do your research before trying this!

[@snellcheeks]

@@LeoMakes Ah right, very informative, thanks for your reply! I don't want to risk any damage to it, so I'm gonna add this regulator. Just to bother you with 2 more questions (sorry for that): shouldn't a heatsink be attached to the voltage regulator, or is that overkill? Q2: the LM7809's are hard to get in the Netherlands, but I see there's an UA7809 available here... is that compatible or even better, the same thing but with a different name? My knowledge about electronics isn't that great. elektronica-online.nl/product/ua7809-7787

[@monomakes]

Thanks for the video, but it would be good if you made it clearer what was going on with the converter board. A schematic would be cool.

[@schtickkicker]

There's a schematic for the converter board at 4:07 and about a minute of description of the parts used leading up to it.

[@MrLanceDaily]

I wonder if this could be successful with an MXR Blue Box

[@ryanpwm]

What about impedances?

[@chriscopeman8820]

I'm going down a similar path. I want a hint for a source for the eurorack power connectors. I've got power supplies, + & - 12V or any other voltages too, but I want to buy the connectors that will work with the eurorack modules I can buy or make. A manufacturers name would help.

[@LeoMakes]

For Eurorack, you can just use straight double-row headers that you can cut to the right number of pins using wire cutters. Alternatively, you can get a shrouded connector that will keep you from plugging it in backward (the ribbon cable can only go in one-way if you have a shrouded connector). To be honest, I just buy whatever is cheap so I don't have a specific brand I can recommend. Good luck with your build!

[@tiefklang]

Thought that the eurorack level is to hot to plug directly into the stomp boxes..?

[@RandomNeeds]

Thank you for the video. I have a question regarding the audio levels, do you find that you need to boost the audio more than usual to match eurorack audio level?

[@LeoMakes]

Hi Ebrahim, good question! I was worried about the input level also, but it turned out work quite well without any modification. If anything, this pedal/module is expecting a guitar input (instrument level) so giving it Eurorack (line level) input might be "too hot" but, again, I think it sounds quite OK. I can always use the module's input gain knob to control too-hot levels.

[@justingaylord9639]

You're using the effect at the end of your chain here, but if you were to patch the Rat's output to another eurorack effect unit then how much amplification do you think might be required to restore the signal to eurorack level? If you ever get a chance to patch the Rat into another Euro effect unit then let us know how it goes.

[@ZeroesandOnes]

Euro is something like 10v peak to peak and IIRC instrument level is about 1/2 volt but I could be talking nonsense (please someone who knows more than me step in!)

[@LeoMakes]

Thanks for watching! You and Justin raise valid points, so I might make some followup videos to address these questions. I've got some other videos in the works right now so it might take a little while... :)

[@pakiw2]

you cannot use same voltage regulator for all pedals, they have to be isolated. each pedal has its own voltage regulator, if not the things start to be awkward - noises, ground loops.

[@LeoMakes]

I've heard this can be the case and I've seen "premium" power distribution systems for pedalboards that have separate regulators for each power output. I can imagine cases where sharing a regulator might be a problem. That said, I did some quick tests on this back in June (when I was making this video) and I didn't notice any obvious problems when I ran this RAT Clone and a Big Muff clone off the same regulator. I'm not a guitar pedal expert by any means so there may be cases where this is really needed to get a good sound but in my informal tests, everything worked and sounded fine.

[@pakiw2]

@@LeoMakes problems occure when more than 3 pedals are used, and also different type ones. Then comes an issue if pedals don't have buffers... 😀 I'm not an expert too, I just ran on that kinda issues, learnt that hard way. At work at moment I'm making koma elektronik field kit fx and erica synths drum sequencer😁👌

[@ManuPro3]

hi, can you give me the precise name or data sheet for the voltage regulator??

[@craigjohnson6867]

Can CV control be added to the pots at all?

[@LeoMakes]

I pretty sure it can be done, but I haven't had time to explore it. It's a good idea and I'll probably get back to it at some point (but I'm not sure when). Thanks for watching!

[@RayMcNamaraMusic]

You can do it quick and dirty style by adding a jack into a vactrol at an existing potentiometer. CV into the vactrol is turned into resistance. Not sure about long term effects, but it works! I'm more of a hack at it 'til it breaks type. haha

[@argumentchannel]

How do you deal with guitar levels compared to eurorack Level?

[@LeoMakes]

To be honest I didn’t worry about it. Most modules and pedals have an input gain so you can turn it up or down to get a healthy level into your product. Basically, it’s never been an issue for me in practice. Thanks for watching!

[@osten5419]

Awesome tutorial and video but you know you could just use a Hendrikson module by Bastl Instruments.

[@arlingtonhynes]

DJ WUD “Did you know people sell Eurorack modules” No, that fact was not previously known to modern science. I salute you, visionary! You’re a regular Prometheus! Why, I’ve even heard rumors that the ProCo Rat pedal can be bought, but that sounds like crazy talk to me. But did you know you can just buy a CD instead of making your own music? Sounds crazy, but believe it or not, it’s true!

[@osten5419]

@@arlingtonhynes I liked your comment.

[@soundmapper]

I came to KZbin wondering if this was a thing.... Yup. :)

[@HashtagPULSE]

Which transistor would this require?

[@HazeAnderson]

TO-92 😏

[@HashtagPULSE]

@@HazeAnderson Cheers!

[@wurzel6857]

@@HazeAnderson since it seems you know about it, is the same transistor stated as Q1 - 2N5457 on the build doc?

[@ZeroesandOnes]

I really enjoyed this and was very educational, but it would be nice to touch on some problems you might run in to with euro level being that much hotter than instrument level - you'd surely need a lot of attenuation on the way in? Can this be done passively? Would definitely love to see more DIY euro/pedal projects though, I know there was some Electro Harmonix ones floating around, and a Chris from Million Machine March recently modded a Korg Mini KP for me: alijamieson.co.uk/2017/12/korg-mini-kp-for-eurorack-modular-kaoss-pad/

[@LeoMakes]

Awesome Mini KP mod--looks really cool! I think passive attenuation would be pretty easy to add in but it works pretty nicely for me without anything, so I didn't bother going any further. Maybe I'll dive deeper into this subject later on, though. I just had an idea: What would be really cool is if I/we/someone could figure out a simple way of adding CV control of the various parameters on these pedals...

[@tegenfase7010]

Some vactrols would probably do the trick. They combine an LED and a LDR into one package, giving you a voltage controlled resistor of sorts. You could DIY them as well by putting these components opposite to one another in some lightproof enclosure (e.g. heatshrink/black hot glue) In the RAT circuit one could put these in parallel or series with the GAIN and FILTER pots. However getting the scaling just right will probably be a pain in the ass... As the LDR will act in reverse of what you actually want (more light is less resistance, thus lower gain/higher cutoff frequency). This can be fixed with some, adjustable gain, inverting op-amps, but to call this a "simple way" might be a bit of a stretch.

[@chupathingy5862]

@@tegenfase7010 Synthrotek sells something called a "vac pac" for just this purpose.

[@anechoicmedia]

a RAT can run at +15vdc no need for a regulator

[@LeoMakes]

You're absolutely right! I knew the Fat RAT would run at up to 18V but a pedal aficionado friend of mine just pointed out that the other RATs can also work at higher voltages as well. I had no idea. Still, I need 9V for the other PCBs I am planning to build and modularize. Thanks for watching!

[@tomvice]

I thought the timbre was voltage dependent

[@johncougar526]

steamorfry it is. The more supply voltage, the more headroom before distortion. I'd suggest making the voltage variable, perhaps all the way down to 5 volts, to get all that wholesome, bad battery squish.

[@josephjankowski1153]

@@johncougar526 Not on a RAT. The RAT produces distortion primarily from diode clipping. The diode transfer function is not based on the supply voltage. It's 0.7v of headroom regardless of how high the supply is. You can get some bad battery squish if you lower the voltage far enough that the opamp starts hitting its rails, but you have to go pretty low.

[@linstate007]

How do you end up mounting pcb to the plate? Switch is holding all of it?

[@halidex]

There were several comments regarding the line to euro levels. I had come across this 1U product that helps with that: syinsi.com/shop/tiles/pedal-io/

[@jackb5524]

no need for heatsinks?

[@LeoMakes]

In this case, there's no need for a heatsink due to the small power requirements (the regulator itself dissipates the heat and barely gets warm to the touch).

[@jackb5524]

oh wow cool, have you tried multiple modules hooked up to the same supply? would it even get any warmer?

[@LeoMakes]

The regulator would definitely get hotter if you draw more current (i.e., more modules), and in that case you might need a heat sink to dissipate the extra heat being generated. That's why the various Eurorack power supplies and distribution boards tend to have regulators with beefy heatsinks on them. If you only hook up one module to those boards, the heatsink would be largely unnecessary, but since those systems have 10+ or more modules drawing from them, then the heat dissipation becomes more important. Hope this clarifies.

[@jackb5524]

Ah yeah, makes sense! Thanks. One more question, do you do any attenuation or amplifying to get the modular signal level down to instrument level? I've poked around on Muffwiggler for an answer but no one seems to know for sure.

[@d42kn355]

I would suggest mentioning that many circuits need power conditioning, and to just use a regulator is a a bit strange.. I suppose youre not utilizing the negative rail but even so.

[@vishnuhareesh281]

you sound like john krasinski.

[@LeoMakes]

You know, if I got a $1 every time I heard that, I'd have a few dollars!

[@baddriddimworkshop]

use your brain what a revelation! this is how you get views in this world; come on!