Modular Synth Masterclass: Build Your Own: Part One (Continued)

David Gale continues this first part of our huge guide to building your own Eurorack Modular Synthezier system…

We just love systems like this

Power
It is fair to say that the power side of a Eurorack system is one of the most important areas for consideration and, certainly among existing users, is the single area that prompts the greatest debate. This is for good reason, as a poor-quality power supply can result in unwanted noise.

If you are intending to fit your own power, the first decision to make is whether to go AC or DC, and for many the idea of playing around with 240v AC, and indeed having a large transformer handling frankly dangerous voltages lurking at the back of your cabinet, may be a no-brainer. At this point, I must clearly state that if you do decide to go down the AC route, you should be competent at handling 240v AC electrics and if this isn’t you, either steer clear or employ someone to check it, or fit it for you.

With the disclaimer issued, it is time to consider what the advantages are. Purists will argue that an AC power supply is better suited to certain modules, and in the case of a larger system, is less likely to result in unwanted noise or earth hums. However, regarding the latter point, AC power supplies are normally placed in the rear of a cabinet and, depending on the size, more than one might be required. Each AC power supply has a large coil, which will produce a magnetic field, so an argument against is that the field may disrupt the audio signal, resulting in unwanted noise.

We love Studio Electronics’ Boomstar modules, and now they’re available in rack form, along with the company’s new Modstar

Once fitted correctly, AC power supplies are perfectly safe to use. The transformer, or multiple transformers, will in turn feed ‘bus boards’, which again are mounted inside the cabinet or case. This is where you plug in your modules, which in turn will draw their power.

As might be becoming clear, AC power supplies seem to be the preserve of the few who feel competent handling 240v electrics, so it is no surprise that buying an AC power supply to fit yourself is quite a flexible affair. We have already mentioned Doepfer, and the low-cost (LC) Doepfer cases all use the Doepfer own-branded AC power supply, which can also be purchased separately.

A very similar design is sold by Clicks & Clocks, and offers lots of useful Eurorack components, especially if you are considering making the cabinet or case yourself. However, the AC power supplies that are considered to be the absolute best are manufactured by Hinton Instruments. Hinton has solutions to all your AC Eurorack needs and can deliver a perfectly clean and regular supply to the largest of Eurorack cabinets.

Switching to DC-based systems, these have moved on leaps and bounds since they first became available, and the convenience of a power supply that is easier to work with at installation may seem like a better solution. The advantage over AC, apart from being safer to work with for the novice, is that there are a number of solutions which are readily available in a plug-and-play format – ideal for the beginner who wants to get stuck in.

Tiptop Audio makes a couple of solutions that are ideal. The uZeus (Micro Zeus) is a plug-and-play solution, consisting of a panel with a power switch and a pair of ‘flying bus cables’, allowing for the connection of up to 10 Eurorack modules.

This can be expanded by adding additional bus cables. The uZeus is powered via a conventional DC ‘wall-wart’ power supply, which is connected directly to the front panel. It’s a minimal-hassle solution for a small system; in fact, Moog recommends this power supply for people wishing to use their Mother 32 Semi-Modular synth in a Eurorack setting with their own case.

If you are aiming a little higher than 10 modules, the next Tiptop solution is the Zeus. This is a very similar concept, with a DC power supply being plugged into a Eurorack mounted switching panel, which is in turn connected to bus boards.

Moog Mother 32, in a three-row format. Complete with three layers of Moog goodness

The boards can then be connected in series using readily available 16 core electrical cable. One particularly strong selling point is the quality of the studio bus boards, that are designed to go with this system. As well as promising a strong and regulated flow of power, they are designed to be very robust, should your system develop a fault. Thanks to three nice bright LEDs, mounted on each board, these will flicker should a problem develop, allowing you to reach for the off switch before any permanent damage is done.

Another very similar system, in concept, is 4MS Row Power. Similar in design to the Tiptop uZeus and Zeus, this system also has the ability to connect from one power panel to the next, reducing the possibility of earth hum issues. For the slightly more adventurous, Synthrotek make a power kit which you can build from scratch.

Not for the faint hearted, Synthrotek’s kit of components offers you everything you need to make your own DC power supply, from the ground upwards. Also reputed to be of good quality, and if you don’t feel like getting the soldering iron out, you can always buy it pre-assembled.

The Pittsburg Modular Cell 90 – expandable, cool aesthetics and a small footprint

Power Supply Manufacturers & Suppliers
● Tiptop Audio – Zeus & uZeus Power Supplies – www.tiptopaudio.com
● 4MS – Row Power – www.4mspedals.com
● Doepfer – www.doepfer.de
● Synthrotek – www.synthrotek.co.uk
● Hinton Instruments – www.hinton-instruments.co.uk

Loading Bus Boards
Whether you ultimately decide to look at an AC or a DC system, you will need at least one ‘bus board’ or ‘distribution board’ (described as ‘distro boards’ by some companies). Traditionally, bus boards are fitted to the base or rear of your case or cabinet, parallel to each row of modules, in order to distribute power to your modules. As such, it is normally the case that bus boards are securely fitted in place.

It is always best to follow the manufacturer’s advice, but methods will vary from the relatively easy double-sided sticky pads to more permanent fixings with screws. Be forewarned, power units and bus boards can get hot, so it is often advised that ventilation holes are in place, especially in larger systems, to allow for airflow around your chosen case or cabinet.

Mounting bus boards with spacers, or standoffs, will help airflow around the boards, allowing them to stand proud of the case by a few millimetres. If in doubt, always follow the advice in the manual of your chosen product. It’s worth getting it sorted from the outset, rather than taking everything out of your cabinet twice!

In the case of the Tiptop Audio uZeus, and some other small power head units, a ‘flying bus’ cable will be used. As the description suggests, these cables are just that, and not rigid in design like their bus board counterparts, but they can be very convenient for smaller systems, and certainly excellent if you’re working to a tight budget. They are also pretty fool-proof, and superb as an off-the-shelf option to get you started quickly.

12V and 5V
While most Eurorack modules draw their power from a 12v DC connection, via a bus board or flying bus cable, some modules may require a 5v connection. These units are very much in the minority and are often of the digital persuasion.

It is worth noting that most Eurorack power solutions include a 5v connector. However, some, such as the Doepfer A-100 power supply, do not. Helpfully, Doepfer also makes a 5v adaptor, that can be fitted, but this is in addition to the main power supply that it manufactures.

And Finally…
The final part of the power equation is to consider the ‘loading’ of your system. The eagle-eyed will notice that while salivating over descriptions of modules, part of the technical specification will describe ‘Power Usage’ or ‘Consumption’, measured in Milliamps (ma).

This is the measurement that is used to describe the amount of electrical current drawn by each module. Some units require more current than others, and your total module current consumption requirements cannot exceed the rating of your nominated power supply. Ultimately, this is pure mathematics! There are 1,000ma to 1 amp, so if you have 10 Eurorack modules, which total 500ma consumption, you will need a power supply with a rating of 0.5 amps or more.

The good news is that the manufacturers understand this, which is why most power supplies tend to be quite generous in rating. One point that you should be aware of when considering your next module purchase is that analogue modules generally require a small amount of current.

However, digital modules often require far more – as much as five to 10 times more, depending on the module. Again, always refer to the manufacturer’s instructions to be completely sure; and, if in doubt, fit a power supply with a higher rating to be safe.

In the next part, we look at modules and examine the bare minimum that you will need to get some useful noise, and consider the options for expanding this to a killer modular set-up.

Pittsburgh Modular makes some of the best rack synths – feast your eyes on this system

One Last Thing: Polarity
One ‘rooky’ (and costly!) error that can easily be made is ‘frying’ a module by connecting the polarity to the bus board incorrectly. The Eurorack format requires that the negative connection, on the module and connected ribbon cable, is at the bottom.

Many companies put a stripe (often red!) on the lower part of the cable to indicate the -12v connection (it’s worth checking that the cable is connected to the module correctly too!). Despite this, it is still possible to connect the Eurorack plug upside-down if your bus boards have exposed pins – which many do – and in doing so may well cause a module to ‘smoke’ or ‘fry’.

Thankfully, this doesn’t tend to be as serious as a fire, but it will render your module unusable, thanks to blown components on the module. Many companies know that this is indeed a common faux pas, and allow for components to ‘blow’, which can then be replaced; but it is a costly mistake, and one that can be avoided by checking carefully before throwing the power switch. Be aware – always look for the stripe!

Next Time: From Cables To Oscillators