Modular Synthesizer Power Distribution

Three Jumpers Jumping

Let's start with the little cables that come along with every module that we ship. These are called "Power Jumper Cables" and have either 3-pins going to 3-pins, 4-pins going to 4-pins, or 3-pins going to 4-pins.

They're referred to as "three to threes" "four to fours" or the crossover type "three to four" Power Jumper Cables.

The latter are the most popular when combined with our Distro Cards because they're so versatile, however if you have a Modcan brand of rack mount enclosure, in most cases you should ask for 3-pin-to-3-pin or "three to three" Power Jumpers.

They are all typically 18" inches long.


There are presently two different types of power distribution boards that we offer...

Original Combo-Distro Card

The first was simply the Combo-Distro Card which ~combined~ the 3-Pin Modcan power headers with the more popular 4-Pin power headers used by other modular companies.

This facilitated the "cynthiafication" of other brands of modular circuits to the Modcan and Cynthia format by opening up the architecture.

The board also introduced a miniature 4-pin Auxiliary Bus to the system allowing the easy distribution of ~pre-patched~ Gate and Trigger signals, as well as up to two different Pitch or Modulation (LFO) signals. The decision was made to add the fourth pin in order to support duophonic keyboards, such as made by Arp, and Aries.

This Auxiliary Bus is used by the Cynthia Dual ADSR modules for example, to link multiple envelopes to a common Gate and Trigger source - simply by pulling-out the ATTACK knob switches on the Envelope's front panel.

The SixPac-Distro Card

Then along came our aluminum SixPac enclosures, and a newer distro card was developed with Duplicate sets of Screw Terminals allowing the ability to daisy-chain a few cards together for smaller set-ups of no more than (3) SixPacs total.

For obvious reasons, these new cards are called SixPac-Distro Cards. They have six of each power header connector type, (instead of eight as the original Combo Distro cards do), and are completely interchangeable with the other cards.

It does not matter which type of distro cards you put into a SixPac. (The actual green or beige color of the boards has to do with what ~batch~ of cards they were made in and has nothing to do with the board type).

When developing the newer SixPac-Distro cards, we wanted to add more current capability fearing that someone out there might attempt to daisy chain more than the maximum of three boards chained together.

This limitation exists because no matter how many boards one might chain together, the very ~first~ board in the chain must handle the current of *all* subsequent boards in the chain.

On a single-layer board there was not much we could do except to remove the solder mask itself to allow thicker metal traces.

Kissing the Ground

Ground is an indefinite voodoo science, talk with four engineers, and you will hear four theories on "proper" grounding.

For this reason, the distro cards have a bus wire LINK to one of the mounting hole pads on the board in order to facilitate grounding of the power supply to the chassis. This Link is easily snipped if desired.

Theoretically, the very best method of system grounding architecture is the "Star Ground Configuration", where there is only One true system ground at the 0-Volts terminal of the power supply. (the Green Banana jack on your Cynthia supply panel).

In a Star Ground Configuration, you would never daisy-chain power from card to card, but instead have all power and ground emanating from a central wiring harness.

On SixPac configured systems of larger than three SixPacs, (or WoodWork cabinets with more than three Combo-Distro Cards inside) it is best to wire-up a terminal block strip to fan out power and ground from a central source.

We sell what we call a "Wiring Harness" for this purpose, which has all of the wires and a special little board with the proper screw terminal strip and mounting holes.

In actual practice, we find that real world systems out there, (as opposed to theoretical) are usually a combination of distribution methods. So if you have a configuration that works... Don't "fix" it!

For example, I have Six WoodWork Cabinets in my own system now, each with it's own power supply. After setting-up the cabinets, I plug all six power supplies into an AC Mains power strip, and then I take a handfull of green patch cords and connect the ground jack from five different cabinets - gathering the cables into the single green jack on the center cabinet's power supply. This forms a star grounding network of six power supplies. Some are Major Supplies, and some are Medium Supplies, that does not matter.

What would happen if I used short cables and daisy-chained the ground from cabinet to cabinet ~instead~ of all of those long green banana cables going to one central supply?

Probably no difference at all, but IF there were by chance any rare noise problems, then I'd try a star configuration as a possible cure.

Supply and Demand

Medium Power Supplies are good for up to about (18) modules maximum. Major Power Supplies are good for up to about (36) modules maximum.

Our Power Supplies are incredibly robust. If there are any shorts in the wiring for example, they will shut down instantly to save your modules. I have to say that with all of the experiments going on around here, we've never had a problem. For this reason I absolutely love these supplies!

As long as you see two Green Lights lit - then you're Good to Go!

(The upper green LED indicates that the Positive side of the supply is working (+15V), and the lower green LED indicates that the Negative side of the supply is working (-15V).

All the components of our power distribution scheme are conservatively rated to provide maximum current handling and protection.

We use beefy thick cable throughout for maximum bass response and current handling.


A new third type of distro card is in development here which may become the new standard. We're waiting for a few test boards to return from the PC board house to see how well the improvements work. For example these are multi-layer boards with more current handling full solder mask, and larger screw terminals that are more forgiving with large diameter wire.

Rest assured that these are all interchangeable!

Hope this answers a few questions!

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