Power supplies choices?

so im starting this topic as I get a lot of questions regarding power supplies, and there are a heck of a lot of options!

the great thing is with this format is the power supply is the same as eurorack. so with that in mind. you can use the options open to eurorack. I guess it limits out things like the 4ms power as that has a eurorack power input module. but there are lots of options!

the go to for me is the mfos style wall wart power supply and I always suggest either the wall wart one by mfos of a very similar one by Frequency central the power diy pcb. these require a hefty AC power brick. But its what I have been rolling with for years.

another option is using a PC power supply I know people have had success with that!

currently I dont have a solution available. but im trying out a few different options and seeing what they are like.

after some research i found the befaco excalibus. its a hefty power bus and to be honest compared to other options it isn’t a bad price! I have ordered one to try with a whole kosmo synth voice and ill do a video with how I get on with it! it uses the same dc to bipolar brick as their jump skiff. but the excalibus is. well at least I think a relatively cheap option. Still quite a chunk more than the wall wart option which overall will set you back about 50 quid after buying the plug and the rest of the components. anyway I will relay back with my findings!

anyone else have any suggestions?


I was just starting to wonder about this. My case will hold 14 10cm kosmos. I have two frequency central power busses, only one built so far. Can I power both busses in series with one wall wart?

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Assuming one AC wall wart and two FC power supplies, and that your wart has enough amps to power both supplies, you can connect them in parallel: same wire from the wart to AC1 on both supplies, the other to AC2 on both supplies. EDIT: See this picture.

If you mix things up, you’ll short the supplies (see this post for why).

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yep as fredrik said! I use 3 amp wall warts and I connect 2 fc power supplies to them each, and the AC1 and AC2 must be the same. if they turn off the second you plug 1 module on 1 power supply into another module on the other power supply you’ve wired em up wrong. (trust me I did it once lol, no smoke tho!)


Only problem there is that PC power supplies use switching, not linear regulators, so there will be high-frequency components possibly messing with things (hopefully inaudible, but…)

E.g. Doepfer’s current supplies use switched 15 V supplies followed by linear regulators to get around this.

(also PC supplies are designed for heavy load on 5 V and not so much on +12 V and even less on −12 V, but if it works it works…)

If you don’t mind switching, a cheaper/more compact alternative to a PC supply is a dedicated triple output supply, e.g. a suitable model from Meanwell’s RT-B series that philippejadin@ mentioned here. Very inexpensive, and a quality brand, but make sure you put it in a suitable enclosure.

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I use the uZeus by TipTop Audio, more outputs than you’ll need as it has 3 busses for ribbon connectors, 13-15VDC 2000mA. pic =>

I also use the Frequency Central MicroBus pic =>
Personally I prefer the TipTop uZeus, but it is really an Eurorack module but it would be easy to mount it (or three :crazy_face:) on a Kosmo format panel :+1:, It’s not cheap but it is a quality build and noiseless :+1:


I’ve been meaning to start an “Adventures in Power Supplies” thread for a while :yum:

I started out with a wimpy 1A MeanWell dual 12v switching supply:

I then worked through several designs and false starts to build my own based loosely on the MFOS LM317/LM337 schematics. I used a 2A center tapped transformer and built it into a repurposed 1989 server supply housing:

I was super proud of that one until it started dropping voltage drastically after 8-10 modules. At first I thought my VCO builds were busted, but turns out the positive supply was down to 6V.

In the meantime, I also built these massive bus boards that I ordered from JLCPCB off files I’d found in the This is Not Rocket Science github repo. Here’s one in the process of being built:

And you can kinda, sorta see one powering my three-row 84HP Kosmo case here:

Before that, I built a bus with indicator LEDs into a old 1U rack unit:

To replace the MFOS supply, I ordered one of the 3A MeanWell supplies:

But I haven’t installed it yet, because this weekend I finally built a thing that had been rolling around in my mind for a while. I found this schematic a while ago in the Intech Studio/Otto’s DIY repo:

It uses two DC wall warts in series and adds 5V with a regulator. Well, if there’s one thing I have enough lying around of, it’s old DC wall warts. So, riffing on this design, I dug out the beefiest ones I could find and I now have +12V@3.3A, -12@2A, and 5V at 5A:

Theoretically, anyway. For now, it works like a charm with very minimal voltage drop with everything, Kosmo and Eurorack, plugged into those massive bus boards. If it starts flaking out, I’ll deploy the new MeanWell as well. And my MFOS supply, I’ll use for the bench :smiley:.


Yes, I’ve got quite a few redundant 12VDC power supplies, so in principle at least I could just use them as part of a +/-12V DC supply. I’d just need to check that none of them are tied to the earth pin in the UK mains supply (instant short circuit, every breaker in the house 15W main turns off.)

I’ll pass on the centre-tapped transformer idea. I like music but I don’t want to bet my competence in electrical power engineering against the possibility of electrocution or fire.

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AVOID this AC adapter if you are in the US and looking for a “wall wart” style ac plug…
I have blown up 2 of them…


I’m using the Frequency Central Routemaster. So far no problems. For cooling of the LM3[13]7 I used some heatsinks I took from a broken PC-power supply I had lying around. The supports I printed using my Prusa 3d-printer. The power supply’s parameters are: +12V 1A, -12V 1A and 5V 100 mA. For my small euro rack this is more than enough.


That’s what I got LOL


me too… but to forewarn you - it is my third… lol (too lazy to search for a new one so just re ordered on amazon each time lololol)

Because of the half wave rectifier used in the AC wall wart style design, that 1000mA transformer can only provide a maximum of 500mA to the +12V rail and 500mA on the -12V rail.
If you want to use the full 1A that the 7812 and 7912 are capable of regulating, you need a 2A transformer.


Could that be because there’s something wrong elsewhere in your system? Jameco is a quality US brand and two of their supplies blowing up sounds fishy.

Great, I just bought a 2000 ma one of these on Amazon. :disappointed_relieved:

I only have had like 4 or 5 modules connected at once, all work fine, only ever been connected to my FC microbus which so far seems to have never faulted. lol
Only thing that has gone has been those ones from amazon.

Could be bottom of the barrel clones??

This look right? Granted I had a 3A wart?

Must be connected in parallel, not in series.
Like @fredrik said above


Yeah, you need to connect the same wart lead to the same AC input on all supplies. Like this:


You’re the man Fredrik thank you bud!