Bill and Will's Synth
"Dragonfly Alley DFA-930"
Inverter / Multiple Construction


January 2008, May 2009 -

We set out to build some multiples or at least to plan for them (we're trying to determine how many 1/4" jacks we'll need overall so we can order them in large bunches and get them cheaper).

While we were thinking about the YUSynth Filter, we thought about how handy it would be to have a few inverters around.  So we planned this module with eight inverters and a four level cascading multiple (the equivalent of a MOTM910).

Table of Contents

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

Background - presents an explanation and Jurgen's initial description of the effect

Parts - presents a Bill of Materials and notes about it

Panel - presents how we came up with our panels' design

Construction Phase 1 - Resistors, Capacitors, IC Sockets, Power Plugs, MTA headers

Construction Phase 2 - Trimmers - OK, this is where we've left off for now



We're going to use two Tellun Industries MUUB4s to build our eight inverters.  Here's what one inverter circuit looks like:

R1 = 100K
R2 = 100K
R3 = 1K
C1 = 22p


The DFA930 uses two MUUB4 PCBs.  Here's how they look:

Image courtesy Scott Juskiw.

Component Layout / Connections

Here's a diagram of the circuitry of the MUUB4 (click on any of these images for a larger one):

And here's a diagram of how the components will lay out on the PCB:

Two MUUB4s are, of course, required. The power input only needs to go to one of the MUUBs; the second can get its power from the first. This diagram shows the power connection and the inputs and outputs from the inverters:

Cascading Multiple

There are four rows left on the panel where we can put a cascading multiple a-la the MOTM-910 only re-arranged a bit on the 2U wide panel.

Paul Schrieber describes it (roughly) this way:

This is "a passive (needs no power) multiple with..." six "...cascaded 4-way multiples. Switching jacks are used to 'daisy-chain' the..." six "...sections together. Inserting a patch cord in any of..." five "...special locations (indicated by the arrows) breaks the chain... to the mults below. In this manner, you can configure..." it "...many different ways:

  • 1ea of 1 in - 18 out
  • 1ea of 1 in - 3 out and 1ea 1 in - 15 out
  • 6ea of 1 in - 3 out
  • and so on.

Here's a diagram of the multiples connections - the view is the back of the panel:

For reference, you can see the wiring of a MOTM-910 here.


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

In the BOM, the left-most column is the "part."  The parts we've ordered have a green background.  These parts we have a high (but not perfect) level of confidence that we've specified correctly.  please double-check us and let us know of mistakes you find.

Corrections to BOM:

None yet -


None yet -

You can click here to download the spreadsheet (apx. 35K).


Scott at Bridechamber made it up for us (he made extras in case you want one).  Here's how it looks:

Construction Phase 1

All the stuff in Phase 1 gets soldered using "Organic" Solder.  At every break in the action, we wash the board off to get rid of the flux.

First, we soldered in these jumpers:

Then these resistors:

The axial capacitors:

IC jacks:

The power elements - electrolytic caps, ferrite beads, MTA header:

Construction Phase 2

All the stuff in Phase 2 gets soldered using "No-Clean" Solder and the PCB doesn't get washed off from here on.

First, we decided to figure out what the length of the connection and power jumper wires should be by temporarily mounting the PCBs on the Bridechamber 3-jack mounting bracket and panel:

Here are the screws, spacers and stand-offs:

Assembled like this:

Attached to the panel with a 112A jack:

We put a length of hook-up in one of the furthest places on the PCB:

That's how we figured out that 7" lengths of coax will be plenty long for the 16 inverter jacks.



ground lead - PCB end

The coax prepared, we soldered them into the PCB:

And then we soldered jacks onto the coax:

With all but the last bit of soldering done, we figure it was time to put the TL072s in:

Then we turned our attention to the multiples.  We used 22ga buss wire for all but the right-most ground connections.  For those, we used hook-up wire (white) so we could wrap the wire around the left of the jacks to avoid the very close right edge of the panel:

Time to solder in the power wires - red for -15V, white for +15V, black for ground:

Then for the inverter jacks.  We started with the three jacks which hold the bracket on - INV OUT 4, INV OUT 6, and INV OUT 8:

Then the rest of the jacks from the lower PCB - IN 5, INV OUT 5, IN 6, IN 7, INV OUT 7, and IN 8:

We screwed on the upper PCB and installed the remaining jacks - IN 1, INV OUT 1, IN 2, INV OUT 2, IN 3, INV OUT 3, and IN 4:



Set up / Testing

Use Notes


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