Bill and Will's Synth
MOTM 830 Two Dot Oh Construction
"Dual Mode Mixer"


We're going go right into building the thing.

Like we did in our first 830, we're going to apply the Dave Brown / Scott Juskiw 830 modifications to our module. So we're going to use 100K1% R8, and R17, and a 49.9K 1% for R18.

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:

Parts - presents a Bill of Materials and notes about it

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

Construction Phase 2 - Trimmers, Panel connections

Set up / Testing

Use notes


Will and I have developed a parts-list / bill-of-materials in the form of an XL spreadsheet based on the parts list in the 420 User Guide.

Click here to download the XL spreadsheet (apx. 350K).

Click here to download the .pdf Synthesis Technology parts section of the User's Guide.

Click here to go to our Bill of Materials Page.

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.

Resistors, Caps, Power, Semiconductors, Misc

As usual, whereas we are vigilant about orienting all the resistors, caps, etc. consistently so their values can be read easily (in case we need to trouble-shoot them later), we oriented the resistors with the "tolerance" stripe on the left (relative to the text on the pcb).  We got started doing it this way when we started building our synth and now we do it so all our modules are consistent with each other.  You might want to do it the opposite way - with the "tolerance" stripe on the right.

We decided to use IC sockets for the two OP285s.  If you're building this, you'll almost certainly be using OP275s - the 285s are extinct.  We acquired a few of the last ones Paul had and we were so nervous about damaging them by accident that we opted for the sockets. 

Construction Phase 2

All the stuff in Phase 2 gets soldered using "No Clean" Solder.


We cut the wires like this:

VR5 - 5" twisted triple Blue, Green, White
VR6 - 5" twisted triple Blue, Green, White
VR7 - 5" twisted triple Blue, Green, White
SW1 - 7" twisted triple Blue, Green, White
SW2 - 7" twisted pair Red, Black
J1 (IN 1) - 7" coax
J2 (IN 5) - 5" coax
J3 (IN 6) - 5" coax
J4 (OUT 2) - 4" coax
J5 (IN 1) - 7" coax
J6 (IN 2) - 5" coax
J7 (IN 3) - 5" coax
J8 (OUT 1) - 4" coax

In hindsight, you might consider making VR7 6", SW2 5", J4 5", and J8 5" - but our lengths worked out fine.

Pots, Wires

Out 2 Jack - Type 114B

Jacks In Panel - Jumpers on Inputs

We soldered the jumpers only into the top (switch) lug so we could easily solder the shield into the angled lug along with the jumper later on.


Will gives a thumbs-up - we're ready to "obseve carefully the wiring order."  Very funny, Paul.

Wiring the jacks


Wiring the switches

The Panel Mount Pots

Construction Done


Set up / Testing

Use Notes


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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

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