A 2026 update of Mesotokyo's cheap power supply for eurorack modular synthesizers.
- Like many people, I have been battling weird, inconsistent power issues in my Eurorack modular setup. The Behringer CP1A and TipTop μZEUS are currently go-to budget PSU's and generally cause few issues. Not so for moi.
- I started building and adapting MST's open-source hardware solution around the same time as implementing a Meanwell RT-65B connected to 240V mains supply in my medium (x4 84HP) wood DIY case.
- I assumed that "More Amps meant More Good" but found there to be significant trade-offs with this setup.
- I forget cables, AC supply and powerboards at venues are 😬, kettlecords (IEC 60320 power cables) are chunky and not long long enough.
- Battery packs are also able to output increasingly high current and, while not ideal, the UGREEN 130W Nexode Power Bank (20000mAh, 72 Watt hours) from Amazon plus PD-protocol USB C-to-2.1mm cable off eBay have been able to run things well playing live in various venues and home studios, lasting ~3hrs 45min powering 27 modules and occasionally other synths/guitar pedals/gear.
- A Very affordable and reliable entry into the incredible world of modular. The most expensive component is the DC-DC isolation + regulator module for the -12V rail and that comes in a fine $5 AUD. All together I'd estimate it's $30 done DIY, possibly less.
- A powerswitch on your modular case is a feature that shouldn't be sneezed at. It's worth 4HP of space.
- Fully filled out supplier parts sheet so you don't have to spec anything - one-click order through JLCPCB.
- Intermediate friendly layout for those wanting to try SMD soldering.
- Lovely poochy paw prints + all the technical details on the silkscreen print.
- Faceplate/front panel can be PCB material, steel or cutout a template to follow and do wood mayhaps (coolguy points).
- 4HP - 128.5mm (H) x 20mm (W) x ~50.5mm (D).
- +12V at 1.5A, -12V at 500mA and 5V at 1A, enough current to supply a small to medium eurorack case, just needs any old external 15-18V DC powerbrick.
- Reverse polarity protection - accidentally using a negative centre powerplug won't do any harm, shorting the supply briefly also fine.
- Will run fine (hotter) on up to 25V DC but voltage will sag at input lower than ~14.7DC.
- Two 16-pin IDC headers on the board - use flying bus-cables or (ideally) passive busboards to distribute this to your modules.
- ISOLATED AND STIFF 12V RAILS!
- Resettable fuse (for transient spikes + inrush current) in-line with an optional 5V supply (pins 11+12 as per Doepfer standard).
- Pass-thru power jack internally/up the back of the device for power supply options. Allows use of one 15V powerbrick to supply multiple power modules.
- build repository here - https://github.com/mesotokyo/cheap-power-board
- changed most through-hole components to SMD.
- matched components to JLCPCB's library and supplier NSLC.
- changed DC-DC isolator to one that is in stock cheaply/easily from Australia.
- moved second DC barreljack to internal and "upper-back-left" to reduce power cabling on front of cases.
- roughed out frontpanel using a blank 4HP and a drill.
- moved components around to fit better.
- tried mounting heatsink to board using solderpoint (NC), found to be mechanically strong but space efficiency preferred by lying down.
- matched pinout of DC-DC isolator to the YLPTEC module, original specced in v0.1 out of stock sometimes.
- added some more text to the board as a guide/self-reminder while building.
- matched height of screws, switch and LEDs to front-panel and designed/printed first prototypes using EasyEDA/JLCPCB.
- fiddling around moving components slightly.
- tracing optimizations.
- specced right-angle 16-pin IDC headers so that euro cables may be inserted more easily in confined cases.
- specced PCB-mount DC 2.1mm barrel-jacks for mechanical strength/manufacturing ease/looks nice.
- some dimensions out between PCB and frontpanel (cursed z axis), reconfigured and printed another 10 prototypes.
- more fiddling/moving components around. Tried putting the big PTC fuse on the right side to prevent electrolytic cap being close to LM7812 (hot) but ended up moving back to left side and moving electro cap further right.
- aligned LM7812 footprint so it can be bent over 90 degrees (lying flat on the PCB) to save space.
- added some more labelling on PCB, particularly the DC-DC module's pinout.
- Widened global track trace-width to 0.75mm from 0.26mm (EasyEDA pro default). When pushing original prototype to failure, only first traces to positive supply DC barreljack burnt out. Soldered solidcore wire onto older prototype's traces as interim solution.
- fixed PCB-mount barreljack pinout, got wrong initially.
- changed unnecessary/problematic GND pins to NC (not connected), namely pin 3 of SPST switch (IMPORTANT - an on/off switch shouldn't short your power supply). Removed pin 3 on previous prototypes.
- very minor tweaks.
- added paw-print graphics to PCB and front panel.
- triple checked alignment and added instructions (Basic BoM.txt).
- added bone-shaped PCB solder mask exclusion to 3M eurorack slots.
- more notes and clearer font on PCB board.
- tweaked LM7812, inductor, electrolytic cap and switch positions.
- pictures and maybe video/audio of fully built/clean/working V0.6 builds.
- usable/meaningful power supply noise measurements if I can get a diff-probe and a better scope or two.
Many thanks to DIY legend MST Mesotokyo for his hard work creating a formidably powerful, efficient, accessible and cheap Eurorack power supply. This has helped me enormously to develop my DIY, electronics and PCB skills and spread my passion for all things synth. :D
Licensed under creative commons.
Build and use at your own risk.
For further notes and build advice, see Basic BoM.txt