Modular Power Supplies


Speaking as a designer, not someone troubleshooting specific power issues, I wonder if DSP firmware can be designed for a more gradual power up.

The ARM Cortex-M chips that I’ve developed on have individual power enables for each internal peripheral. Of course, it’s common to immediately turn on every peripheral interface that’s needed, but it seems like it would be possible to have a time delay in the firmware startup such that the inrush current would not be so drastic.

I guess the real question is: How much of a problem are DSP modules and initial power draws? If it is a significant problem, then it might be worth pushing manufacturers to update their firmware. We humans won’t notice a few extra milliseconds - even hundreds of milliseconds - at startup, but the power supply would!


Hardware makers: throw more hardware at it!


That works for analog modules. However, I’m fairly certain that a digital module that needs a lot of current at the start will freak out with soft start. Instead, it’s necessary for the digital firmware to control the current draw on the “load” side rather than have soft start on the “supply” side.


Something like this was happening with the Teensy 3.6 when I put it in the Teensy 3.2 slot in my TXo module. In order to use the 3.6 (and get the extra horsepower), I had to make a little daughterboard with a voltage supervisor that delayed the start of the Teensy using the reset pin. Not all Eurorack power supplies caused this, but enough did that it was critical to implement the workaround. (It was maddening until I found the thread over at the teensy forum and the solution suggested by user neutron7 - J.Matheson, creator of the Orgone Accumulator.)

Here is the silly little board I made for the workaround:


sorry, I didn’t fully explain the concept. since most modules already have a 2x5 male connector, each 1x5 row could accept a 1x5 cable - only one 1x5 row is needed to power Module A, so a second cable could connect the unused 1x5 row to Module B to carry power down the line in a marginally more graceful and easy to rearrange manner.

I’ve made plenty of my own daisy chain cables and am using 2 or 3 now, but in many situations it is hard to connect various modules together due to the lack of consistency in power header placement/orientation and I end up needing to make new cables to connect different placements of modules when I swap out a module or rearrange my case. sometimes the modules that I want to chain aren’t next to each other - I try to isolate my digital modules from analog to avoid noise issues, for example, so my daisy chains sometimes have to leapfrog other modules on a separate power cable due to where I want them ergonomically.

granted, some completely reasonable solutions are to simply use such daisy chain cables, passive bus boards, or flying bus boards to split power when one has plenty of power but not enough sockets, but I could imagine a use for a lower-profile solution to try to make a case as slim as possible.

also, there is something that irks me from a purely conceptual standpoint about the design decision to use the 2 row ribbon cable for Eurorack power and this felt like an idea which could, at least in concept, be a more logical solution (removing the redundancy of two separate, side-by-side wires carrying the same power/ground/signal to the same place) while remaining backwards compatible…but I also acknowledge that there likely isn’t much appetite for a widespread change at this point.

in any case, using a single 1x5 row to power 1U and small 3U modules (2hp and similar) does offer the advantage of taking up much less space on a PCB.

I readily admit this is a nuanced and sort of stupidly specific issue! I’m also thinking of this in part as I would like my next case (if I end up building or buying another at some point) to be as low profile as possible, and minimizing excess volume taken up by power cables and power supply PCBs would help with that.


It’s certainly a todays reality but unless your are running at the limit of your PSU - I don’t think it’s a huge problem. Only few modules are known to be really problematic in this regard (I’m looking at you, Roland Aira range). People are hacking their power supplies with additional capacitors to ease the peaks. But sure, if you are hardware designer and can come up with better power rails that survive whatever you can throw at them - that would be awesome. :ok_hand::wave::clap::yum:


I was thinking more along the lines of designing the modules themselves to draw power more gradually during startup. After startup, if the power draw is too great for the power supply, then you simply need a bigger power supply. I might have gotten the wrong impression, but I thought that one of the problems mentioned was modules that draw a huge, but temporary, in-rush current.


Jumping in on this bit of the thread, I am also interested in solving a power / ground problem.

I have a Rene in a DIY skiff which is not responding very well to touch unless I actively hold on to one of the rails with my other hand (one of the workarounds recommended by MN as I understand it).

While that does work for interaction, the other issue I see is that there appears to be ghost triggers occurring, as if I were touching the key pad, even when I’m not - a built in source of uncertainty right there I guess but not quite what I’m liking for :slight_smile:

The skiff is powered by a Synthrotek PWR module (not the Deluxe Power, but the earlier DIY model), which came to me with a bunch of other power parts, including a power brick that seemed a bit questionable.

I got a Meanwell GSM60A12-PJ1 to replace the random power brick, and I can see on the specs list that this as has -ve connected to the AC frame.

The new power brick hasn’t improved the Rene’s behaviour on it’s own. Trying other power outlets hasn’t improved it either.

I could try grounding a rail with a wire to something large, instead of having to hold on to it myself.

I’m up for replacing the PSU or replacing flying bus cables with a better bus board but Rene seems to be a fussy enough module that I could go through a few things that may not make any difference, so I guess I’m trying to understand the issue better to start with. It seems to be s common enough issue, but I haven’t yet found much that helps me understand the situation.

If there’s any good resources that people here can point me to, I’m all ears.


keep eliminating the variables. can you try the module in another case? i’d suspect your power module itself.


For sure. I have tested with a 4MS RowPower 40 in place of the Synthrotek and had similar issues with Rene, even though other folks report no problems with a RowPower. My next step is to replace the flying bus cable with a proper bus board, though I have learnt on this thread that not all bus boards are equal. I’ll also try some kind of grounding arrangement from the rail in place of myself, and will report back.

At the end of the day there seems to be lots of variables. I feel like I already have a functional “workaround” - it’s just not very ergonomic. But then again neither is a cello and I learnt to play that back in the day :slight_smile:

It’s all a process of learning so I don’t mind encountering a few challenges along the way.


I would connect it with ground of the PSU. Would that improve things? Not sure about this with switching PSU…