This guide is intended to help you building the Ultima Ratio Eurorack Module from a Kit.

Introduction and Disclaimer should not discourage you

The Ultima Ratio is considered to be an easy to intermediate build with a low part count.
All components are "through hole" and there is no wiring involved.
Still, some of the solder joints on the IC sockets and headers are very close to each other and you should have enough practice to solder these without shorten them out. The warranty covers only defective parts (those you didn't destroy yourself), so you have to be confident in your skills and know what you are doing.

That said: if you manage to build your Ultima Ratio you will feel like an evil mad scientist. So heat up your soldering iron in your secret vulcano missile base and go for it!

In the Box

Gezeiten Ultima Ratio
See Bill of Material

Required Tools

  • Standard Pliers
  • Cutting Pliers
  • Soldering Iron + Solder
  • Small flathead Screwdriver
  • Eyeprotection (really!)

Step 1: Resistors

Start with soldering the resistors on both PCBs

  • 220 Ω: R1-R13
  • 1 kΩ: R14
  • 4.7 kΩ: R15
  • 10 kΩ: R16, R17, R18
  • 1 MΩ: R19

Be patient with R16, R17, R19. These resistors are connected to ground on one side. That means the solder will not "glue" as easily. If you have problems try to increase the heat on your soldering iron for these joints.

Gezeiten Ultima Ratio

Step 2: Diode and Crystal

Solder the diode and the quarz crystal on the small PCB.
Orientation of the crystal does not matter but on the diode it is vital!
Align the stripe on the diode with the mark on D1 on the PCB.

Gezeiten Ultima Ratio

Step 3: Power Regulator

Bend the legs of the power regulator with a plier to 90 degrees... Gezeiten Ultima Ratio

... and solder the power regulator on the small PCB.
Be prepared, the middle pin is connected to ground and therefore the hardest pin to solder. Gezeiten Ultima Ratio

Step 4: IC Sockets

Check the orientation of the IC sockets IC1 and IC2 and allign the notches on the PCB. Put them in the PCB, turn the PCB upside down and solder swiftly and confidently the 14 plus 28 solder joints.
Double check for any shorting!

Gezeiten Ultima Ratio

Step 5: Headers

There are three header connections on the PCBs: One with 4, one with 8 and one with 10 pins.
Connect all the male and female header parts, then stick them in the PCBs. Female headers are connected to the large PCB.
Do your best to keep the PCBs as parallel as possible and solder all the joints (22 on each side).
It may help to just solder the two outer pins on each header first and then continue with the remaining ones.

Gezeiten Ultima Ratio

Step 6: Transistor

Carefully pull the PCBs apart again.

Solder the transistor Q1 on the large PCB.
Orientation is vital, align the transistor with the marking on the PCB.
This is a thermal critical part, so don't apply too much heat.

Gezeiten Ultima Ratio

Step 7: Capacitors and Power Header

1. Solder the two small ceramic capacitors C3 and C4. They have the same specs. Orientation does not matter on these.

2. Solder the double row 10 pin male power header.

3. Solder the electrolytic capacitors C1 and C2.
C1 is the smaller 3.3 μF capacitor, C2 is the bigger 33.0 μF capacitor. Orientation is vital on these!
The longer leg is +, so put the short leg in the square hole labeled as -.
There is also a stripe on the capacitors which should face to -.

Gezeiten Ultima Ratio

Step 8: Debug LED

Solder the red LED on the small PCB. Orientation is vital: the longer leg goes into the square hole.
This LED is only there for debugging purpose, but I recommend to solder it anyway. Gezeiten Ultima Ratio

Step 9: Prepare the Potentiometers

Prepare the four potentiometers by clipping the upper unnecessary thingies with a cutting plier.
Wear eyeprotection! These things are deadly shrapnels.
Edit: it may also be possible to just bend the thingies several times back and forth with a standard plier until they go off.

Gezeiten Ultima Ratio

On one potentiometer (Clock Divider 2) also clip the leg. This is important, else the leg will shorten some resistors which are in direct proximity when mounted.

Gezeiten Ultima Ratio

Step 10: Mount the Hardware

Mount all potentiometers, jack sockets, the switch and LEDs, but don't solder yet.
When you are done the PCB should look like the image below.
Read ahead for instructions on how to mount the different parts.

Gezeiten Ultima Ratio

10.1 Potentiometers

Mount the potentiometers by applying some soft force and they should click in the PCB.
The potentiometer with the clipped leg is the second from left in the image below.

Gezeiten Ultima Ratio

10.2 Jack Sockets

Mount the jack sockets on the PCB. Every socket has three pins, the external ground pin is facing up to the top of the PCB.

Don't solder yet.

Gezeiten Ultima Ratio

10.3 Switch

Mount the switch. Orientation does not matter. Don't solder yet.

10.4 LEDs

Stick the green LED to LED1 and the two blue LEDs to LED2 and LED3.
Orientation is vital. The longer leg of every LED goes into the square hole which unfortunately is hard to see. Everything is right if the long legs face "north" to the top of the PCB.

Don't solder yet.

Step 11: Faceplate

Instead mount the Faceplate carefully.
If everything fits put the nuts on the potentiometers, on the switch and on the jack sockets and tighten them.

Gezeiten Ultima Ratio

Turn the module upside down. The LEDs should fall into the drill holes in the Faceplate through the miracle of gravity.

Don't solder yet.

Gezeiten Ultima Ratio

Step 12: The Bridge of Sorrow

Due to a software change of the Reset functionality you have to apply a bridge to the Ultima Ratios reset jack socket to reflect that change on the hardware side.
To easily do this you can craft a small bridge from one of the clipped legs of a resistor in the shape of an U.

Gezeiten Ultima Ratio

Stick your bridge in the pin holes on the PCB for the RESET jack socket.
This might be fiddly, be patient and you will succeed.
As an alternative you can just solder a small wire between the pins of course. But resist your urge to just dump a large clot of solder on to it.

Regardless of how you do it, you have to shorten the external ground pin with the next adjacent pin on the the RESET jack socket.

Gezeiten Ultima Ratio

Step 13: Solder them all!

  1. Solder all three LEDs
  2. Solder all five pins of every potentiometer
  3. Solder the three pins of the switch
  4. Solder the three pins of every jack socket, pay attention to the Bridge of Sorrow
Gezeiten Ultima Ratio

Step 14: ICs

Gently push the 14 pin DA converter and the 28 pin microcontroller in the sockets of the small PCB. Orientation is VERY vital.
Align the notches on the ICs with the notches on the sockets.

Gezeiten Ultima Ratio

Step 15: Knobs

Put the knobs on the potentiometers and use a small flathead screwdriver to tighten the screws.
Typically it is best to leave some space between the knobs and the potentiometers to prevent grinding of the knobs.

Gezeiten Ultima Ratio

Step 16: Finish him! Also congratulations, you did it!

  • Stick the PCBs together.
  • Connect a cable to the power header, Red Stripe down!
  • There is no calibration necessary
  • Mount the completed module in your rack, switch it on and pray play.

Appendix

Troubleshoot

If something is not working as expected, as always, check your solder joints first.
Look for cold joints or shortened ones.

Nothing happens
1. Check for the right orientation of the power cable.
2. If the red LED on the backside of the module does not light up, something is not right on the small PCB.
The LED for Clock Divider 2 does not light up
Did you solder the Bridge of Sorrow?
When I turn the Clock Divider 1 knob tempo AND Clk1 change simultaneously?
That's a feature, not a bug. It only happens when no cable is connected to the IN jack due to the lack of available knobs. Check Mode 2: Clock Generator in the manual.

Bill of Materials

Amount Part Type Label Properties
1 Electrolytic Capacitor C1 package 100 mil [THT, electrolytic]; capacitance 3.3µF; voltage 6.3V
1 Electrolytic Capacitor C2 package 100 mil [THT, electrolytic]; capacitance 33µF; voltage 16V
2 Ceramic Capacitor C3, C4 package 100 mil [THT, multilayer]; capacitance 15pF; voltage 0.1kV
1 Rectifier Diode D1 package 300 mil [THT]; type Rectifier; part # 1N4001
1 Atmega328 IC1 package dip; version Atmega328-20PU; type ATMEGA328; variant dip28 THT; part # ATMEGA328P-PU
1 MCP4922 IC2 package DIP (Dual Inline) [THT]; hole size 1.0mm,0.508mm; true; pins 14; pin spacing 300mil
1 Green LED - 3mm LED1 package 3 mm [THT]; leg yes; color Green (570nm)
2 Blue LED - 3mm LED2, LED3 package 3 mm [THT]; leg yes; color Blue
1 Red LED - 3mm package 3 mm [THT]; leg yes; color Red
1 BF245C N-channel FET Transistor Q1 package TO92 [THT]
13 220 Ω Resistor R1-R13 package THT; tolerance ±5%; bands 4; resistance 220Ω; pin spacing 400 mil
1 1k Ω Resistor R14 package THT; tolerance ±5%; bands 4; resistance 1kΩ; pin spacing 400 mil
1 4.7k Ω Resistor R15 package THT; tolerance ±5%; bands 4; resistance 4.7kΩ; pin spacing 400 mil
3 10k Ω Resistor R16, R17, R18 package THT; tolerance ±5%; bands 4; resistance 10kΩ; pin spacing 400 mil
1 1M Ω Resistor R19 package THT; tolerance ±5%; bands 4; resistance 1MΩ; pin spacing 400 mil
1 Voltage Regulator - 5V package TO220 [THT]; voltage 5V
1 Crystal package THT; frequency 16 Mhz; type crystal; pin spacing 5.08mm
1 Generic double row male header - 10 pins package THT; hole size 1.0mm,0.508mm; row double; form ♂ (male); pins 10; pin spacing 0.1in (2.54mm)
1 Generic male header - 10 pins package THT; hole size 1.0mm,0.508mm; row single; form ♂ (male); pins 10; pin spacing 0.1in (2.54mm)
1 Generic female header - 10 pins package THT; hole size 0.7mm,0.508mm; row single; form ♀ (female); pins 10; pin spacing 0.1in (2.54mm)
1 Generic male header - 8 pins package THT; hole size 1.0mm,0.508mm; row single; form ♂ (male); pins 8; pin spacing 0.1in (2.54mm)
1 Generic female header - 8 pins package THT; hole size 0.7mm,0.508mm; row single; form ♀ (female); pins 8; pin spacing 0.1in (2.54mm)
1 Generic female header - 4 pins package THT; hole size 0.7mm,0.508mm; row single; form ♀ (female); pins 4; pin spacing 0.1in (2.54mm)
1 Generic male header - 4 pins package THT; hole size 1.0mm,0.508mm; row single; form ♂ (male); pins 4; pin spacing 0.1in (2.54mm)
1 DIP socket - 14 pins Example
1 DIP socket - 28 pins Example
4 Knobs E.G. Volcano knob VC-MINI
4 Potentiometers 10k Ω linear E.G. Alps RK09L1140A66
1 Switch SPDT On-On E.G. Gemini A101SYCQ04
8 Jack Sockets - 3.5mm E.G. Thonkiconn

Ultima Ratio on ModularGrid