Now available: Ouroboros Gemini PCBs and front panels.

Gemini is a beginner-friendly DIY synthesizer existing at the crossroads of a primitive rhythm box and a chaotic west-coast system. With a low part count consisting only of common thru-hole components and a pre-drilled front panel intended for mountable legs; Gemini is a very approachable and ideal entry into the world of synth DIY while also being a very worthwhile instrument in its own right that would still satisfy an advance builder. Gemini consists of two individual resonant low pass filters which are each pinged by separate LFOs to create percussion such as clicks, crackles, pops and bubbling sounds inspired by Serge and Hordijk sonics, as well as rudimentary bass drums, toms, rim-shots and claves akin to those of early drum machines. The LFOs each have gate outputs and rate modulation inputs, and there is a third, slower LFO with a gate output as well which can modulate either or both of the other LFOs. Using the banana jacks, the LFOs can be patched together to create syncopated rhythmic interplay between the two resonant voices or patched to create modulated patterns of spontaneity and unpredictability.

The resonance on the filters can also be brought into self-oscillation, and one of the voice's LFO can be brought into audio rates for thick, acidic bass drones. Individual outputs allow the possibility of panning and processing each voice individually. It can also be connected via an optional ground jack for use when cross patching with other banana gear. The Gemini PCB and front panel set is now available for $50USD + $8.50 shipping within the US.

To order - email: ouroboros.electronics.us@gmail.com

or you can order through the listing on Reverb.com:

https://reverb.com/item/42283365-ouroboros-electronics-gemini-pcb-front-panel-diy-synth-kit


Gemini is based off of an previous one-off instrument that I made; the Dual Resonant Voice: It is exactly the same with the exception of the new enclosure and a slight tweak to one of the voices to provide more sonic variety.




Ouroboros DIY KIT BOM:

(Quantity x component description followed by recommended part #)


3 x White Banana Jack

108-0901-001


2 x Black Banana Jack (+1 extra if you want a ground jack)

108-0903-001


2 x 3.5mm mono jack

MJ-3507


7 x B100k 9mm Potentiometer

P0915N-EC15BR100K


7 x Knobs

1900-H


1 x Battery Snap

BS61


1 x Red LED

LTL2R3KRD-EM


2 x IC INVERTER

CD4069UBE


2 x IC Socket

110-13-314-41-001000


1 x 120uf Capacitor

UPW0J121MDD


2 x 100uf Capacitor

USF1C101MDD


1 x 10uf Capacitor

UST1E100MDD1TP


6 x 0.1uf Capacitor

K104K15X7RF53H5


7 x 10k Resistor

MFR-25FBF52-10K


4x Hex Standoff

4506-440-B-12


4 x Hex Nut

9600





Ouroboros Gemini DIY Q&A:


Q: Is the Gemini a good DIY project for beginners?

A: Yes! The Gemini is a simple and straightforward project with a low part count that will be approachable for beginners, but still a worthwhile build for more experienced builders.


Q: Around how much will the project end up costing?

A: Assuming you already have a soldering iron, solder and the basic tools required - the pcb/front panel set + all of the components required for the build will end up costing less than $100 total. Of course this will also depend on which exact components you buy (you can cut some costs by selecting cheaper components) and where you buy them from, plus shipping and tax, etc.


Q: Do I need to order the exact components listed in the BOM, or can I use other components of the same type and value? Can I choose other cheaper components to save money?

A: Aside from the ICs which must be the exact ones which are specified in the BOM - you can use different components with the same values. Just make sure the voltage rating is high enough and other specs are comparable, and the parts are roughly as small as or smaller than the parts specified so that they fit well on the PCB and in the enclosure.


Q: The knobs specified on the BOMs are pretty expensive, could I order some different ones to cut costs?

A; Definitely! The knobs are the second most expensive part after the PCB and panel itself. As far as cutting costs, you can save a significant amount of money by choosing different knobs than I specified, which will be very pricey if you are not buying in bulk. As far as selecting alternative knobs, just be sure to look at the datasheets and make sure that the knobs will fit onto the potentiometers.


Q: What do I need besides the PCB/front panel?

A: You will need to order all of the components listed in the BOM, as well as a soldering station (preferably with adjustable temperature). You can pick up a Weller soldering station at Home Depot for around $40 to get started. You will also need some lead-free solder, wire, wire snippers, needle nose pliers, and a 9v battery. Additionally, you may want an anti-static bracelet to use while handling the chips, and a solder sucker for any mistakes that happen while soldering. After you have finished building it, you will need two 3.5mm to 1/4" cables to connect the Gemini outputs to your mixer or audio interface. You do not need any banana patch cables to use the Gemini, but it makes it more fun! I'd recommend either making or buying three 6" banana patch cables to patch it with.


Q: Is the Alea thru-hole or are there surface mount components as well?

A: The Alea uses only surface mount components.


Q: I don’t know how to solder. Is there any hope for me?

A: Yes! Watch a couple of Youtube videos and buy yourself a soldering station and some solder. Practice soldering some with wire or old spare components, and then once you’re comfortable, you should be able to take on the Gemini.


Q: Where and how should I source the parts?

A: All necessary parts should be available via digikey.com. You can copy and paste the part numbers from the BOM (listed below) into the search and it should pull up the correct part, then you just have to enter the quanitity (specified by the BOM) and enter it into your cart!


Q: How to I know which way to insert the components into the PCB?

A: The components should all be inserted into the top side of the PCB - the side with the text and footprint of the component on it. Some components such as the electrolytic capacitor will have a ground symbol on one side of the footprint. You will want to insert the short leg of the component into the side with the ground symbol. There is usually a ground symbol on the correlating side of the capacitor itself to assure you that you’ve inserted it correctly.

The LED will need to be placed on the board following these same rules - with the short leg next to the ground symbol on the board. All of the other components are non-polar and do not need to be placed on the board with polarity in mind.


Q: How do I need to position the ICs on the PCB?

A: You will notice there is a notch in one side of the ICs on both the PCB footprint as well as the sockets and the ICs themselves. Make sure the notch in the socket matches up with the notch in the footprint, and make sure you insert the ICs into their sockets with the notch matching the notch in the socket, and they will be positioned correctly.


Q: Do I need to worry about the ICs being damaged via static shock from my touch?

A: Yes, an anti-static wristband and other anti-static precautions should be own while handling the chips to avoid damaging them.


Q: How do I connect the banana jacks?

A: You can connect them via wire going from the jack to the large circular holes/solder pads which each jack goes through, or you can bend the ends of the jacks down (once all of the jacks as well as PCB are all mounted in an enclosure) and solder the ends of the jacks directly to the circular holes/solder pads. I personally bend the ends of the jacks down and solder directly to the pads, but connecting all of the jacks to the pads via a short bit of wire can be a safer and easier route to go when it comes to disconnecting and reconnecting the jacks from the pcb for troubleshooting on the front side of the PCB (incase that happens to be necessary). The one exception to that is the pad next to "SQR OUT" that will need to be connected via wire to the banana jack on the top left for the square LFO output where the cutout in the board is (since that jack couldn't fit fully on the PCB).


Q: I finished building my Gemini, but something is wrong. How should I troubleshoot it?

A: If it doesn’t appear to be working at all, or something is significantly non-functional, then I recommend checking the polarity of the battery snap leads, then checking the orientation and individual legs and solder points of the ICs and IC sockets. Your ICs may have been damaged by static shock, and if so, then they will need to be removed and new ICs should be inserted using an anti-static wristband. If something minor, or one aspect of the synth seems not to be working, then I suggest checking over each solder joint and orientation of the components (making sure negative leads are inserter correctly, etc). Sometimes, after a long day of soldering, it’s best to just take a break and sleep on it, and it’ll be easier to evaluate everything and continue troubleshooting the next day. Please feel free to send me an email if you are having any problems and I will do my best to help out!


Gemini Diagram:

Please note that Ouroboros Electronics does not accept returns on DIY materials and do not accept responsibility for non-functioning builds.