Bill and Will's Synth
Our Medium Size Synth
Power Distribution

Early on, our plans were smaller - our synth plan just a little more than a Synthi-A's worth of modules and so, for power, we only planned on a 900 (+/- 15V) and also a 950 because the 510 Wave-Warper and 650 Midi-CV converter we ordered would require the +5V 575 ma power of the 950; and because we needed more 15V supply as well (+/- 15V, +5V).

But as our plans evolved, and our system grew to nearly the functional equivalent of a Synthi-100 and to be housed in four separate cabinets, we figured we'd need more power.

Exactly how much power?

Well - that's an interesting question.  Our ultimate design includes modules we won't be building for a while and that we don't even show yet in our synth design on our main synth page:

Table of Contents

This page has become really long, so here's a table of contents that we hope will make it easier to traverse:

Background - presents our thinking about our power distribution system

Parts - presents a Bill of Materials and notes about it

Indicator LEDs -

Construction -

Set up / Testing

Use notes


So we're building this chart to do a nearly accurate calculation.  For the modules we don't really know the value for we took a guess on the high side and marked them with a tilda.

Module Width Power
+15 -15 +5
Top Left Case - top row
1 JH Living VCO 7U 90 90 -
1 Fritz TZ VCO 2U 90 80 -
3 MOTM 300 VCO 6U 135 135 -
2 MOTM 310 VCO 2U 45 45 -
1 MOTM 910 Multiple 1U - - -
Top Left Case - second row
1 MOTM 101 Noise S/H 2U 30 30 -
1 MOTM 520 Cloud Generator 2U ~35 ~35 ~300
1 Mancato VCF 2U 35 33 -
1 YU CV Standards 2U 50 50 -
1 MOTM 120 Sub Oct Multip 2U 25 25 -
1 MOTM 730 VC Divider 2U 15 15 75
1 YU Saw Animator 1U 45 30 -
1 MOTM 830 Mixer 2U 15 15 -
1 TLN 904 Veeblefetzer 1U 50 14 -
1 TLN 867 Tuner 1U 45 27 -
1 MOTM 910 Multiple 1U - - -
Top Left Case Totals 695 609 375

Top Right Case - top row
1 MOTM 320 VCLFO 2U 45 45 -
2 MOTM 390 µLFO 2U 30 30 -
1 MOTM 380 Quad LFO 1U 12 12 -
1 MOTM 820 Lag Processor 2U 25 20 -
1 Oakley OMS820 1U ~25 ~25 -
5 MOTM 800 ADSR 5U 50 25 -
2 MOTM 850 Pedal Interface 2U 20 20 -
1 MOTM 650 MIDI/CV 2U 35 20 300
1 Oakley OMS EFG 1U 16 16 -
Top Right Case - second row
1 CGS Analog Logic/Dual ASR  2U ~30 ~30 -
1 TLN 904 Veeblefetzer 1U 50 14 -
1 Buchla 292c LPG 2U 16 16 -
1 MOTM 700 VC Router 2U 30 30 -
1 MOTM 510 Wave Warper 2U 22 22 -
1 TLN 712 Doomsday 5U 150 150 -
1 JH Frequency Shifter 4U 111 106 -
Top Right Case Totals 667 581 300

Bottom Left Case - top row
1 MOTM 410 VCF 2U 20 20 -
1 Oakley410 1U 18 17 -
2 MOTM 420 VCF 4U 36 36 -
1 MOTM 440 VCF 2U 25 25 -
1 MOTM 480 Resonant Filter 3U 25 25 -
2 MOTM 485 GX VCF 2U 40 40 -
1 MOTM 490 Moog VCF 1U 15 15 -
1 TLN 904 Veeblefetzer 1U 50 14 -
1 DFA Inverters / Multiple 2U ~15 ~15 -
Bottom Left Case - second row
1 YU Fixed Filter  4U 57 57 -
2 JH Polymoog Resonator 6U 42 40 -
1 JH Varislope Filter 3U 85 85 -
1 JH String Filter 2U ~30 ~30 -
1 Polyvoks VCF 1U ~20 ~20 -
1 YU EMS VCF 2U 30 29 -
Bottom Left Case Totals 508 506 0

Bottom Right Case - top row
1 MOTM 910 Multiple 1U - - -
1 RB Mix / Comparitor 1U ~15 ~15 -
1 TLN 904 Veeblefetzer 1U 50 14 -
1 MOTM 830 Mixer 2U 15 15 -
1 TLN 861 Dunsel 1U 38 38 -
1 TLN 862 Lag Processor 1U 38 38 -
1 TLN 863 Max Min 1U 15 15 -
1 TLN 864 Switching Compar. 1U 15 25 -
1 TLN 866 Gate Processor 1U 82 47 -
1 JH Scanner Chorus Vibrato 4U 50 48 -
1 TLN 156 Reverb 3U 70 70 -
Bottom Right Case - second row
1 JH SOST Flanger 4U ~70 ~70 -
1 JH Subtle Chorus 2U ~35 ~35 -
1 JH Triple Chorus 2U ~35 ~35 -
1 JH Krautrock Phaser 2U ~75 ~75 -
1 JH Tau Pipe Phaser 2U 33 30 -
1 MFOS Panner 1U ~20 ~20 -
1 MOTM 100 VCA 2U ~15 ~15 -
2 CGS Tube VCA 2U ~30 ~30 -
1 MOTM 190 VCA 1U 15 15 -
Bottom Right Case Totals 751 635 0


We ordered four power supplies from Paul - two each of the 900s and 950s - so we'd have four panels - one each for our cabinets with plug, fuse, and switch.  But instead of mounting the power supply units and power distribution boards on the panels, we'll mount them separately in the cabinets. 

Each 900 has an HAA15-0.8-AG dual Power-One (click here for .pdf spec sheet). Each 950 has an HTAA-16W-AG Power-One  (Click here for .pdf spec sheet).  We'll put one HAA15-0.8-AG and one HTAA-16W-AG in each top cabinet (that's where the +5V is needed).  In each of the bottom cabinets, we'll put an HBB15-1.5-AG; 1.5 amps of +/- 15V.



We want to have LEDs to indicate when the power is on - green for each +15V "rail," red for each -15V "rail," blue for each +5 "rail."

We didn't know exactly how to go about it, so we asked Dave Brown. He wrote us back:

"LEDs on all three supplies is a good idea. I always make sure that there are modules on every power supply that have LEDs. The brightness of the LED will tell you that the voltage is reasonable, but not accurate. For example, if for some reason the +15 was only at +12, the LED brightness would probably be indistinguishable.

"...Sometimes a power supply will "crowbar" meaning the inrush current was sufficiently high that it goes into current limit. LEDs will tell you that they all came up.

"Figure out how much current you want to drive the LEDs with for a reasonable brightness. If they are all the same, then make each of the currents be the same. LED brightness varies with color and efficiency so I run my blue LEDs on much less current. Also, the voltage drop varies with color.

"Assume a standard red LED with 2.0 volt drop. 3 - 5 mA would be enough current.

"For the +15 volts supplies: (15-2.0)/5 mA = 2600 ohms. Use probably the next higher value, so 2K7. Use this for both the + and - 15 volts supplies. For the -15 volt supply, just turn the diode around. Connect the cathode to -15 and the anode to ground.

"For +5 volts, you want the current to be the same. Use the same formula to find that resistor. Using 2K7, (15-2.0)/2K7 = 4.8 mA. (5-2.0)/4.8 mA = 625R. Use a 620 ohm resistor.

"You could probably get away with higher resistance values. It depends on the brightness you want."

But we're total idiots so we asked Dave to show us exactly how to do it.  We mentioned that we were going to use a blue LED for the +5V indicator.  He reminded that these are a little brighter that the green and red.  He provided us with this little diagram - thank goodness - easy as cake.  (Thanks Dave!)


Here's the distribution plan for the top cabinets:

Here's the distribution plan for the bottom cabinets:

Power cables illustrated...

The above synth layout (four cases - each two rows high and 18U wide) can be accomplished with a couple power cable layouts.

One uses all standard 20" MOTM power cables, but with two distribution points. This may have advantages, given power distribution considerations:

Another layout is with mostly 20" power cables (red), but some custom  24" cables (or 30" cables) (green) and centrally located distribution. 


Will and I have developed a parts-lists / bill-of-materials in the form of an XL spreadsheet.

Click here to download the spreadsheet (apx. 250K).

1/2 in spacers and 1 inch #6 screws for the distribution boards

1 in nylon spacers and 1-1/2 inch #8 screws for the power-ones


OK - the cabinets built, it's time to empower them.

Distribution Boards

We attached the distribution boards to the tops of the cabinets.  Starting with the upper two cabinets— here's how we layed out the distribution boards.  Upper-right cabinet first:


holes marked

we drilled pilot holes

screwed down the distribution boards

top left layout is the opposite - there's a slight advantage in this because of the location of the modules that need the +5V. 

screwed in...

In the case of the bottom cabinets, the layout is simpler - it's shown later on this page

The Power-Ones

They were connected to the AC power using the switch/plug/power-panels we got from Synth Tech and incorporated into our case designs.

the grounding wires got connectors soldered to them

we connected them to the power-one cases like this

and then we connected the power lines

The upper cabinets:

We mounted the power-ones so their calibration variable resistors are accessible from the rear of the cabinet

here's how they go in the upper-left cabinet— one of the power-ones had been part of a traditional MOTM 900 power module

with the power lines attached and screwed down to the case

the upper-right cabinet has the power panel on the opposite side

Here's what they look like with the power-ones and distribution panels

The bottom cabinets:

We connected the power-ones to the AC power using wire-nuts.

We adjusted the voltage to satisfy ourselves we'd done it all correctly. Worked like a charm.

Distribution Wiring

We soldered pan connectors to distribution wires

Then starting with the upper cabinets, we ran the distribution wires from the distribution boards to the power-ones first the upper-right one.

We ran the distribution wires around the side of the cabinet opposite the AC power panel and we figured it out so none of the wires had to cross each other in the process.

Then the top-left cabinet

Connecting the Power Ones

The distribution wires get soldered to the power ones.  First, a bottom cabinet.

The top cabinets have the two power ones.

One of the power ones was used in a stock MOTM 900.  Rather than unsolder the connections, we soldered on pan connectors to do the job.

Jumper cables for the power delays

We made little cables to connect the poser delays in line

Power indicator LEDs

Then we prepared the LEDs with resistors in line pre our diagram (far) above.  We cut the wires to 28 in.

The LEDs went into the cabinets' center facings.

First we drilled holes for the screws that would attach the facings to the cabinets.

The we threaded the LED wires through the indicator holes in the facings.

We attached plugs to the LED wires

And bound them together with ties.

We put the facings in place - threading the bound LED wires around the brace like we had planned.

And we plugged them in.


Some of the LEDs didn't light when we tested them, but we fiddled with the plugs and found loose connections. In the end, all the power ones, the power delays, and the LED indicators worked great!

Set up / Testing

Use Notes


Bill and Will's Synth Main Page
Send eMail to Dragonfly Alley

The fine Print:
Use this site at your own risk.
We are self-proclaimed idiots and any use of this site and any materials presented herein should be taken with a grain of Kosher salt. If the info is useful - more's the better.  Bill and Will

© 2005-2011 all frilling rights reserved