Pet Rock

eurorack friend

by Jonah Senzel

Pet Rock is a rogue-like rhythm generator which changes daily, with monthly modulations in style.

batch 2 of Pet Rock is now available for pre-order,
$30 for kits, $35 for assembled modules

(Pet Rock is sold at cost of production)

buy here from synthcube

(currently sold out, but sign up for restocking updates here)

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↓what is it?↓

here's one day's Pet Rock rhythm, used in 3 different ways, accompanied by my friend Daniel Paleodimos, who kicks ass, think of it as a man-machine rhythm duet

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redmeansrecording did an amazing video on it

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This 4hp Eurorack module generates a new rhythm every night at midnight that you have 24 hours to use. Pet Rock is like rhythm Wordle - everyone who owns the module gets the exact same rhythm. No internet connected needed.Pet Rock has 2 independently clockable (gate in, gate out) 'A' and 'B' rhythms each day, so there's flexibility in how you use it/clock it. The ‘A’ and ‘B’ rhythms can be used together as one composite rhythm, split into two separate rhythms, etc.Rhythm generation parameters change according to the real current moon phase. The overall "Mood" changes with every 30 day moon cycle to help keep things fresh. With each “Mood” change, Pet Rock switches between several custom algorithms to produce distinct styles.

for questions and concerns email me at

Discord --->

<--- Email

(for some more theoretical talk on cost, read here)Pet Rock is sold at cost. What that means is a little more complicated than I originally thought. The price of this module will probably change over time (if I end up making more than my initial run of 40) Here are some of my questions and complications:One Time CostsMany costs of Pet Rock are one-time, like money I spent during the development of the module, so how much money I add to the cost of the module to recoup them would depend entirely on how many modules I sell. I’ve decided mostly to think of these one time costs as money I’m willingly putting into the project, it’s not a crazy amount of money, let’s call it less than half of one op-1 field’s worth. My final production cost of the modules ended up at around $20 - this is with little margin for recoup (in the manual I quote $18 including $2 recoup fee). The retail cost of $30 comes after a distributor fee of $10, which is pretty standard percentage wise as far as I've heard.Some unexpected One-Time costs- massive and random customs import fees- Modules breaking over the course of production- lots and lots of extra labor due to a mistake at the circuit board factory forcing me to re solder a tiny component on each board. And also due to some stupid clerical errors i made in board design that needed to be corrected- me buying some things on amazon for more money than i could have if I was patient and bought from a slower shipping storeLaborLabor on Pet Rock so far has been my labor. I have worked for free. Besides some help on T shirt design and Video (which was from friends who I paid mostly in beer) I have made everything in Pet Rock. All the hardware, all the software, the front panel design, the stickers, the manual, the website, and the assembly of each module. I have chosen to not pay myself for that. I don't see Pet Rock as a money seeking endeavor. As I explain in my manifesto, and in my writings, I am curious about Eurorack for Eurorack sake, and what it means to put out a module because I want to put one out having nothing to do with wanting to make money. The first run of modules is 50, 10 of which have been lost in the great war of me fucking up and JLC fucking up. If this thing becomes moderately popular, frankly, I'm kind of screwed hahaha - but if that happens maybe I'd have someone help me assemble, and that person will definitely would definitely be paid. As I say in the manual, the only reason that I do all of this for free as well, is that I already have plenty of income from my job as a composer. The concept of this new, no profit Eurorack, is about people who don't need to make a living from it.Luxury costsSome costs I'm not including are "Luxury Costs" things I didn't need to spend money on to have a module out. In my case that includes any and all promotion costs. So I paid some money for promo, and paid to exhibit at Knobconn, but I'm considering this a luxury cost, that I'm doing for my own benefit and fun, because it is. I'm not making any money off this anyway, so I don't need any promotion at all, I'm doing it because I think it will be fun and I want people to see this thing that I'm making. Also, little tip here, I decided to exhibit at knobconn almost entirely because it was a real life deadline, that I had to show up to in person, for which I would pre pay things like my table and hotel etc. - so that made it an actual deadline that I had to stick to, which was very instrumental in me finishing the whole project.What's up with the whole moral angle here, wise guyI think of this project as one experiment in how to do pricing totally differently than the rest of Eurorack. There are many others. People have pointed out that, if I want to increase accesibility, Eurorack is a bad place to do it, because you need to have so much invested to even want a module. People have told me that the only people buying this are going to be rich already, that I'm basically just selling something cheap to people that need it the least. And these people have a good point. I really just have been flabbergasted by the price of Eurorack since I started looking into DIY. Like many things, I have the great king HAGIWO to thank for this, who opened my eyes to the fact that most eurorack modules do not in fact contain any platinum inside of them, and are $7 of components slapped together behind a faceplate (really though, is there anyone cooler than HAGIWO). I felt like the whole industry was kind of a lie, like a hundred sweaty manufacturers all side eyeing each other and whispering "don't let the secret out, it's just an arduino with 4 thonk jacks attached to it". I think that was kind of a snap judgement, but the frustration at how inaccessible the format was stayed with me for longer. So this particular experiment is a direct reaction to that feeling I had.Here are some other experiments you (or maybe I in the future) could try, that would explore the accesibility of Eurorack- Sell a module at normal market price publicize all of your finances, including costs and profit, etc for your business (and if you're in individual, for your life too). This is my general response to the idea of a normal for-profit Eurorack business. If I'm going to pay $600 for a single module, I kind of want to know where my money is going. If I'm paying to put food in your mouth that's ok, I want to see it.- "community copies model" Sell a module at normal market price, take all of the profit you make doing that, and use it to make more copies of that module. These extra copies are given away for free to people that apply for a free module, given that they meet some sort of criteria, like being low income, etc.- Sell a module at normal market price, use 100% of the profits for charity- "one for them, one for me model" alternate between releasing a module that is very weird and experimental and fun, sold at cost, and a module that is sold at market value that is very practical and sought after, from which you keep the profits (certain module types, like a good and compact multi channel audio interface, would be easy to undercut the market with, since no one is making a decent one for a reasonable price)

NOV 20th 2023 Update

greetings earthlings! update - batch 1 (~500 units) is slightly delayed from what I expected , still looking on track for January, December may be overly optimistic. Some people may get their units earlier than others. New preorders will also open soon, hopefully in the next few weeks. The good news is once its out, I can start cranking out batches much fasterWhy The Delay:#1 power redesignIn my initial small run batch, 2 of the units died during use because of a poor choice on my end using too small of a power regulator, which in turn overheated and failed. No one reported any damage to any other part of their system, and the issue seemingly only happens when the module is powered for long periods (in one case overnight, in another case ~2 weeks straight). Both units were replaced for free - anyone who has a V1 module that experiences a dead module can email me and I will send you a newer module for free. This was an oversight on my endbecause of this, I decided to redesign a small part of the board to better handle heat, and I also replaced the power regulator with one that is rated for higher temperatures/longer use. I have now succesfully left the new design on for 3 weeks straight, without issues (this test, as one may imagine, required waiting for 3 weeks). That doesn't mean it's going to be completely bullet proof for all heat situations, but as far as I can test, and with the constraints of the board size, it seems to be an acceptable fix for nowhuge huge thank you to the discord community for helping with all sorts of stuff solving this issue, and reporting it in the first place!#2 small redesignsI also have made some other small improvements to the board, like smaller board pads for the jacks on the PCB, to help align the lights better, and also added support circuitry to inputs for plug in detection, as a futureproofing measure for some possible software updates I have kicking around in my brain#3 factory scalingI now have to make one more "test run" - which will probably be the first 100 shippable orders of this next batch- the factory just informed me that they only support "reordering" on specific types of orders (basically those with 50+ pieces) - reordering is when you can directly re-buy a prototype you've already tested and received without having to reupload all the files and re-confirm placement of each part with an engineer - this confirming process is often where tiny details get messed up on either end, so skipping it massively improves your chances of a no hassle production run. So I'm planning on ordering 100, then re-ordering more. It's also just a lot more complicated to order larger batches - now instead of being lumped in with all the other tiny orders, I have my own production run at the factory, which means I have to deal with all the ins and outs of mass production - details that used to be taken care of for me are now up to me to decide/figure out. I'm also dealing with parts shortage and having to order extra parts to be waiting for me when I order#4 life!I continue to do my lovely job as a composer/sound designer for Daniel Mullins Games, been travelling, been living, been working on Pet Rock through it all - and also dreaming of starting prototypes on a new module, but holding out until things start shipping.The support and kind words of so many people have made me feel incredibly happy and fulfilled. And they have validated my feelings that Eurorack can be a "bonsai project" for people with jobs/stable income. I like not having to care about profitability, or maximizing anything, the freedom that comes from that - I like that the project is about my love of the idea. I was initially worried that it would feel great to announce a project like this at cost, but be a slog to make it real - that the fun of being controversial would wear off. But I actually feel the opposite - now that I'm scaling up and doing the real production stuff, I feel like its even more fun to make this naïve idea a real thingBest!- Jonah