Choosing a Eurorack case

Molten Modular 04 – Choosing your Eurorack case and power supply

Right, modular then, we’re going to need a case. This is undoubtedly the first barrier we hit on our road to modular loveliness. It can be a bit mind-boggling but before we can start using modules we’re going to need a Eurorack case to put them in and a power supply to make them light up.

It has historically been very DIY – so not only do you need to be an electronics engineer to understand modular but you also need to be cabinet maker to make the case to put it all in. There’s a large amount of this going on – and it’s awesome. You couldn’t ask for a more extraordinary hobby than building yourself a synthesizer. Am I allowed to call it a hobby?

But hopefully, I’m trying to show, that it doesn’t have to be this way – and that’s ok. Not everyone has the carpentry skills to build a case – and that shouldn’t prevent people from entering this world any more than playing the guitar doesn’t require you to build one. There’s a range of decent off-the-shelf options so you don’t have to do it all yourself – unless of course you want to.

So if we don’t have to worry about building one then it’s more about making the right decision on the size, shape and powering needs of the system you’re trying to build.

Video version below – text continues after…

So what are these cases about? Well, these modules are 3U tall, with only a front panel and are designed to sit in a rack like other audio gear. The width of the modules is measured in HP which may mean horizontal pitch or hole point, it doesn’t really matter, but when Doepfer designed it 5HP equalled one inch giving you 95hp in a standard 19″ rack unit. Simple modules are commonly 4hp wide – wide enough for a decent sized knob and a jack socket or two. More complex ones tend to be 8hp, 12hp and as big as you like my Mother-32 here being 60hp

Your Eurorack case can be as simple as a set of rails on an audio out-board style rack, but more commonly they are built into boxes and skiffs, flight cases or sometimes beautifully made wooden cabinets. You can easily shell out over £500 for a decent case, thousands for a big one – this is just the case, you haven’t put any sound making modules in there yet – so you can see why people would resort to making their own out of cardboard or Ikea drawers.

So let’s try to get this a little more under control. There are a number of more pocket friendly options that are slightly more modest in size that are perhaps a better way to start than an enormous 12U behemoth. Although one piece of advice to bear in mind that I hear a lot is that you’ll always need a bigger case.


The literal idea is that it’s the size of a box in which you’d pack your sandwiches. Typically these are around 40-54hp in width and so could realistically carry half a dozen modules, or lots of little ones. These are more commonly used by people with bigger systems who want to take a handful of modules out for a gig, or connect various lunchboxes together. If it’s your entire rig then it’s not going to have a whole lot going on in there.

Doepfer box

The A100 range from Doepfer are, I guess, the original Eurorack case. There are posh flight-case style options or much simpler and cheaper ones made of untreated wood. These can look a bit like a suitcase of modular, or maybe a guitar cabinet. The untreated ones are ripe for customisation – in fact Red Dog has a great blog post on how to add metal corners and a handle to a basic doepfer case. On the one hand they are a bit unlovely, but they can also be a bit edgy, rock ‘n’ roll and portable.


A skiff, I think, tends to refer to a single 3U row enclosure, often 104hp wide, that sits flat on the desktop. They tend to take up less space and be a bit cheaper than most. They don’t always have the depth of an upright case so you have to be aware of the depth of your modules just in case they won’t fit.

TipTop Happy Ending kit

This is probably the best budget route. It’s some rack ears with rails between and a built in power supply for £140. It’s designed to fit in a regular 19″ rack, although it’s completely happy sitting on your desk, you just have to cope with all the wires and ribbons hanging out the back. 19″ will give you about 95hp of room, which isn’t half bad and is half the price of many other options. Tiptop have developed a future looking case called Mantis, which has 2 rows of 104hp in a plastic shell that’s fully powered and can sit at interesting angles. It’s the sort of innovative case that I think we’ll start seeing a bit more of.

So what did I do?

Well as I mentioned in my last video my starting point is the Moog Mother-32. Now that semi-modular synth is 60hp wide which puts me in a bit of a dilemma. Any decent sized case I buy is going to have a large chunk of it used up by the Mother-32. If I get a 104hp skiff I’ll only have 44hp to play with – which simply isn’t enough for what I want to do. Well Moog have a sneaky and quite cost effective solution. They offer a 60hp Eurorack case that can fit to the Mother-32 with a pair of brackets for a cool two tier system – in fact they also do a three tier which would give you 120hp of space on top of your Mother-32 – plenty! I have ummm and arrrr about this for weeks. It seems like the perfect solution – it’s affordable, expandable. But every time I look at my Mother-32 it just looks small and I feel I would outgrow that space pretty quick. So, taking the advice to always get a bigger case I’ve discovered that Moog also do a 104hp case for not too many pennies more than the 60hp. Then if I keep the Mother-32 out of it for the moment then I have a whole 104hp to play with and if I spill over into another 104hp case then I can incorporate the Mother-32 neatly back into it. Sounds like a plan and honestly , if you come up with a plan then your best bet is to stop thinking and go with it.


Right, let’s check the pricing. My aim was to get a case solution for under £300, because if I was willing to pay more I could probably get something quite posh. 1 x 104hp Moog case – £109, brackets £47, PSU – £79, wall wart £10 giving me a total of £245. That leaves me room to expand at a later date and end up with a nice looking, wood-ended, angled console modular system with the flippin’ word MOOG written on the back. Even thinking about it now I keep flip flopping to a simpler, more rock-n-roll square case that might be more mobile…. But then I don’t like the poor access to the knobs – I like the console style…. Aaaaa.

Power Supplies

So these are a pain in the arse. You might expect them to come with the case and would not normally be something you’d have to worry about, but that’s not always the case. It’s taken me a while to tease out from people exactly what this is all about. I hear it time and again that you need to make sure you get a beefy PSU – but no one ever explains what that actually means in terms of physically available PSU product. I went to a great lecture at the SynthFest last year where a bunch of modular luminaries gave some great information for getting into modular and they talked about the importance of the power supply – but again they just said it was vital and important but gave no other detail. So… do we have to hand wind our own transformers or what?

No, at least not any more. A Eurorack power supply is made up of three parts. There’s a bus board which gives a load of ribbon sockets for your modules to plug into. This is connected to a transformer which provides the +12 and -12 volts that most modules require and usually a 5v as well. Finally you have the wall wart – usually a laptop style power supply, bringing the power in from the wall socket. Now which part of this has to be “beefy” is not entirely clear but the rule of thumb is that to have a happy system you need to add up the power requirements of all your modules and it mustn’t exceed the power available on the power supply. Simple yeah?

So how the heck do you know that? If you’re starting out and buying a case and a couple of modules how on earth are you going to know what power you’re going to need by the time you’ve filled it up? Most cases do seem to come with a power supply, or a choice of one and you’ve got to assume, haven’t we, that they will be suitable and up to the task for the number of modules you are likely to install. Or that the shop you buy it from will sell you an appropriate one.

I’m not promoting a DIY approach to power supplies here – I don’t have the experience or the courage to do that. There’s a lot of information on the Muff Wiggler forum – I know, terrible name but it’s the best forum for modular – that goes into massive depth on power, distribution and connectivity. But I’d suggest it’s for people who are really doing the whole thing themselves. The rest of us – just get it off the shelf!

The reality is that there’s actually only one or two to choose from that are readily available from modular shops. There’s the MicroZeus from TopTop audio and then there’s the beefier one from 4MS that can handle double rows. From what I’ve seen most people using a single row skiff are using the uZeus – and it’s very cost effective. The 4MS comes in two versions, the Row Power 30 which is equivalent to the uZeus and the Row Power 40 which they reckon could power more than 200hp of modules, so 2 rows of 104hp shouldn’t be a problem. All of these power supplies come with the flying loose bus board ribbons. This, for me is the best solution for a modest case.

It’s at this point that I will introduce you to the most marvellous resource on the entire internet –

Modular Grid is an extraordinary website that lets you build your dream modular system right on the webpage. You can lose hours in here dropping in modules and working out what’s going to fit in your chosen case. Then you choose a larger case and start again. But what’s really important here is that it totals up the power consumption as you go. So you can see exactly how much power your selection of modules is going to need – that’s phenomenal. It’ll also give you a price which is flippin’ alarming.


If you buy a case from a shop then they should be able to supply you with the right PSU. If you need to buy a PSU separately then get the Tiptop or 4ms one. If you are building some huge wall of rails then I suggest you talk to a specialist about powering it properly. Use to test out the size of your case and play with combinations of modules.
Right, it’s finally time to start talking about modules….