Sunday, 1 June 2014

What Power Supply does my Modular Synth use?

  The Power Supply Comparison
This is a follower to the previous synthesizer module size post.
There are an ever growing number of manufacturers and many different PSUs (power supply units) to match.
This is a brief comparison of the main brands.
Do email me is there are any mistakes or recommended changes.(I'll try to keep this page up to date).

Most use a regulated dual polarity PSU.

Analog Solutions                                        +/-12, +5V
Analog Systems                                         +/-12, +5V
Blacet                                                         +/-15V
Buchla                                                        +/-15, +12V +5V 
                                                                   (+24V - rarely, in a few 200 modules)
BugBrand                                                   +/- 15v
Driscoll                                                       +/- 15V
Eurorack                                                    +/-12, +5V
Cyndustries                                                +/-15V
Doepfer                                                      +/-12, +5V

Metasonix                                                   12VAC  (D-1000, S-1000, KV100 
                                                                                    and TM modules)
                                                                      +/-12, +5v (Eurorack format modules)
Modcan                                                      +/-15V
Moog                                                          +12V, -6V , -10V
NonLinearCircuits (NLC)                              +/-12V
Paia                                                              +/- 15V
Serge (Sound Transform Systems)             +/-12V (+6V in early paperface systems)
--------------------------------------------------------------------------------------------------------                                        +/-15/+5V
Synth Tech (MOTM)                                      +/-15V
Synton                                                         +/- 15V (Fenix II/III)
Technosaurus                                              +/-18V
Wiard                                                            +/-15V

Useful links for building DIY PSUs.


Buchla Power Supply conventions 

These PSUs changed over the decades so are confusing at times.
As I work my way through the modules that I own I'll update this post.
Please let me know if there are any errors.

Buchla 100
+15V, +24V, single ground.

Buchla 200 (early - Black Knob modules)
+15V, -15V, +/-24V, +5V, -5V, dual ground

Buchla 200 (late - "blue knob" modules)
+/-15 volts, +5 volts, +12 volts and 2 ground lines

Buchla 200e
Power on a Buchla 200e module is delivered from a  edac 306-010-500-102 connector.
The 200e cases come with a12 volt DC wallwart that connects to 3 DC-DC converters.
This is much safer & probably also helps in reducing background noise.

I've made some backup Buchla power supplies and the DC-DC converters  that I have successfully
used are:Cincon CHB75-12S05 (for the 5V),and two CHB75-12S15 for the +15/-15 lines.
CHB75-12S12 for the +12V.
If +24 is requited use a CHB75-12S24 DC/DC regulator. These codes are Mouser numbers.
1 Black - quiet ground
2 White: -15
3 Red: +15
4 Dark Green: +12
5 Orange: +5
6 Brown: noisy ground
7 polarizing key - no connection (use this to correctly orientate the EDAC.)
8 Yellow: i2c clock
9 Green: i2c data
10 no connection - (I often use this for supplying +24v)


Non Linear Circuits 

RED = +12v


GREEN = -12V

These are pics from my first NLC system.
 Basic but works. Becareful of exposed wires ... they will kill.
The transformer is on the left.

The Power One Data sheet


Serge Power Supplies.

Serge being mostly DIY in the early days is super confusing and some of the early paperface
panels used whatever colour wiring was available at the time.
I have a number of early paperface panels and some use different colour codes

Early Serge (Paperface) number 1.
This used +12v, -12V, +6V, one ground.
 The Serge colour convention on this old synth is:
-12V - White
+12V - Black
+6V   - Red
  0V   - Green

Here is a second system I have.
It's from the late 70's or early 80's I think ..

A post shared by jono (@dj_jondent) on

This used the following colour code

Red = +12,
White = -12V
Black is ground.
You can always double check by looking at what the pads on the PCB are labeled.


Early serge panel # 3

A post shared by jono (@dj_jondent) on
The current Serge PSUs use these types of cases:

This is a PS4A - enough power for 4 panels
The connectors are 5 pin DIN connectors

There is an inline AC/DC converter with a grounded
AC wall cord at one end and a Molex connector at the other designed to
mate with the distribution board inside.

The power connectors  for these modern panels look like this:

Sound Transform Systems offers a “M-Boat” chassis.
It is approximately 17” x 7” x 4.5” in dimension.

MBoats have a central power/indicator (called the “Obelisk”)
which has LED indicators for +12/-12v, as well as a power LED.
PSD vs Obelisk
the psd (power supply distribution) is for shop panels while the Obelisk is for m-odules. The obelisk contains a PSD like distribution board - but with only 4 connectors instead of 5.

Power Connector
The standard inter-connector used by STS is a Tyco Rectangular 4 pin Connector. The body and pins are sold separately.
Pin & Socket Connectors PLUG W/O EAR 4P inline is PN: 770078-1
Pin & Socket Connectors 24/18 AWG TN/BR SKT is PN: 770146-1
Pin & Socket Connectors RECPT 4P DETENT LOCK in-line is PN: 770075-1
Pin & Socket Connectors 24/18 AWG TIN/BRASS is PN: 770147-1
The PSD has the female connectors.

Pin 1 is at the point. Pin 4 is at the flat (for both male and female).
Pin 1 = Ground 1, Black
Pin 2 = -12V, White
Pin 3 = Ground 2, Green
Pin 4 = +12V, Red

STS also uses a 5 pin XLR connector for power distribution. Coming from the power supply (PS4 for example) is a 5 pin female XLR. It is intended to be plugged into a panel mount 5 pin male XLR connector which then terminates to a male Tyco Connector (for plugging in power to the PSD). I used an Aphenol panel mount 5 pin male XLR connector, PN: AC5MDZ for a replacement part and it worked fine.
Here is what my PS4 XLR connector pinout is (note, I am not sure if this is standard or not, i would assume it is, but I dont want to be responsible for plugging anything in backwards):
Pin 1 = +12V, Red
Pin 2 = Ground 1, black
Pin 3 = -12V, White
Pin 4 = Ground 2, green
Pin 5 = Not Connected


EuroRack PSUs.

The first rule one must never forget is the stripe = -12V.
When I was a newbee I made the cardinal error of plugging in my module backwards.
Mostly, the stripe will be red, but sometimes it's blue.
As eurorack manufacturers don't have to comply to any laws re the position of the stripe
it's really up to you to check with the manufacturer what the correct orientation is.
So be careful when you plug your module in for the first time.

The power distro bus is usually made up of 16 DIP header pins (2 rows of 8).
I've also see some older distroboards made from 10 pins (2 rows of 5).
Most these days ccome in the 16 pin format.

Counting from the -12V pins, the bus goes thus:
1.  -12V
2.  Ground,
3.  Ground
4.  Ground
5.  +12V
6.  +5
7.  CV
8.  Gate

So your PSU needs to supply +12,-12, & maybe +5v.
The connections between the module & bus is achieved with a 10 or 16 ribbon cable.
This is a 10 wire cable. for a module that only uses +12,-12.
The 10 pin header fits into the module & the larger 16 goes to the bus board.


Pin 1 : +12V (red)
Pin 2 : Ground (Green)
Pin 3 : -6V (Blue)

-10V is used on some modules.
================================================================== (Dot Com).
6 pin MTA female

1= +15V White
2= Key
3= +5V Red
4= Ground Black
5= -15V Green
6= No connection

MOTM - Synthesis Technology

-15V , Gnd, Gnd, +15V

Mos Lab :
+12v/-12V see above
The Kobol VCO is +/-15V

The Oakley power buss comprises of +15V and -15V lines with two grounds. These grounds are not connected together as in the MOTM. They are joined only at the power supply in pure Oakley Modular.

Modcan A & Cyindustries (Cynthia)
The Modcan-A format uses a module height of 9", and a horizontal unit of 2.25". Banana jacks are used.
A yellow jack indicates an output of some sort;
A gray jack is a signal input;
A white jack indicates a control voltage input;
A red jack is a trigger or gate input.

The format uses ±15V power. The power connector used is a 3-pin MTA-156 connector.
It's very similar to the MOTM format, in which a distribution board connected to the power supply is connected to modules using short power cords with female connectors on both ends.


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