Schematics, eagle files and build notes for the umodular

As promised, attached to this post you’ll find the schematics in PDF and the eagle files for the umodular. Released as open source hardware, so hack away and please provide feedback! The eagle designs are not editable using the free version because of the size of the PCB, sorry. Check the list below; one of the outstanding wishes is to divide the large board into smaller, attachable boards – all below the 100mm x 80mm constraint.



Following is a list of todo’s, build notes and other observations I did while building the prototype. Future versions will include features and fixes from this list.


vco: own design, open source and open source hardware

vco: replace CA3046 with modern matched transistors BCM847DS

vco: pulse should also work, even without controlling it through PWM width with a voltage

vco: triangle out

vco: sine out

vco: trimpot for base frequency

vco: option to follow osc 1 pitch

vcf: for now working with MFOS “Simple State-Variable VCF” design, open for non-commercial use but © Ray Wilson

vcf: replace ray’s filter with own variant

vcf: voltage controlled resonance in LP filter

vcf: more filter options (BP, HP, LP)

vcf: dual filter?

adsr: Working with a design by Rene Schmitz, permission for use granted.

adsr: vc for d and s?

vca: cost effective to develop version without THAT 2180?

mix: Update mixer volume control. Sounds like highpass filter now

pcb: all TL274 -> TL074

pcb: fix potentiometer orientation. All pots are inverted! full left is now +5 should be -5

pcb: check log pot instead of lin pots

pcb: footprint 78xx != footprint 79xx! Replace footprint of 7909 with actual footprint!

pcb: a nice manual routing, reducing the amount of via’s. Busses for power.

pcb: general layout

pcb: add small capacitors for decoupling

pcb: integrate Arduino more

pcb: split pcb in two for better shipping etc? multiple parts, max 100*80 to also enable eagle free software

pcb: add designators for capacitors! value, type and placement. For all components!

power: work on a DC adapter solution

power: replace the 6 3300’s with 6×1000’s because 2×3300 seems to be enough power

functional: Have “standard” switchable (flip switch) connections between vCO’s VCF VCA and mix out

functional: Dual/triple VCO mixer

functional: all individual modules with dedicated cv and audio paths? Save in shipping, saves in prototyping costs.

functional: have a module connector with +9v, GND, -9v and 4 audio and 4 cv paths. Modules can grab audio or cv from one of the paths and return audio or cv on the paths.

functional: 4 oscillators with LFO switch

func: digital LFO using Arduino


vcf: 560nF -> 560pF

adsr: replace 10uf with 10nf or 1nf

adsr: R72 -> 1k

adsr: R86 -> 1k

vca: 1n34a -> 1n60 (1n4454)

vca: QUAD_OPADMPP TL274-6A should be non-inverting

vca: add 100ohm to GND and 1000uF to GND inbetween TL274-6C out and THAT2180A pin 2.