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

The guide is for the revised version 1.2 of the PCB. This should be labeled bottom right on the smaller PCB.
If not, see the instructions to build the older version.

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

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See Bill of Material

Required Tools

  • Standard Pliers
  • Cutting Pliers
  • Soldering Iron + Solder
  • Small flathead Screwdriver
  • Eyeprotection

Step 1: Resistors

Start with soldering the resistors on both PCBs

  • 220 Ω: R1-R12
  • 1 kΩ: R13
  • 4.7 kΩ: R14
  • 10 kΩ: R15, R16, R17
  • 1 MΩ: R18

Be patient with R15, R16, R18. 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.

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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.

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Step 3: IC Sockets

Check the orientation of the IC sockets IC1 and IC2 and align 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!

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Step 4: 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 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 -.

3. Solder the double row 10 pin power header. Be careful to check the right orientation, else the keyed power cable won't fit later.

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Step 5: 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 6: 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.

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Step 7: Transistor

Carefully pull the PCBs apart again.

Solder the transistor Q1 on the large PCB. Orientation is vital.

Normaly you have to align the transistor with the marking on the PCB.
But unfortunately the orientation on the PCB does not match with the pinning of the provided transistor.
You have to mount and solder the transistor rotated by 180° like in the photo shown below!

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Step 8: 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 should also be possible to just bend the thingies several times back and forth with a standard plier until they go off.

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Step 9: Mount the Hardware

Mount all potentiometers, jack sockets, the switch and LEDs, but don't solder yet.
Read ahead for instructions on how to mount the different parts.

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9.1 Potentiometers

Mount the potentiometers by applying some soft force and they should click in the PCB.

9.2 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.

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9.3 Switch

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

9.4 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 10: 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.

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Turn the module upside down. The LEDs should fall into the drill holes in the Faceplate through the miracle of gravity.
Cosmetic: if you don't want that the LEDs protrude the panel, temporary put a stripe of adhesive tape on the panel.

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Step 11: 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.
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Step 12: 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.

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Step 13: Knobs

Just put the knobs on the potentiometers.
Typically it is best to leave some space between the knobs and the potentiometers to prevent grinding of the knobs.

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Step 14: 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 play.
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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
Check for the right orientation of the power cable.
When I turn the Clock Divider 1 knob I can select max 2-3 divisions!
Did you solder the transistor rotated by 180° ?
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-R12 package THT; tolerance ±5%; bands 4; resistance 220Ω; pin spacing 400 mil
1 1k Ω Resistor R13 package THT; tolerance ±5%; bands 4; resistance 1kΩ; pin spacing 400 mil
1 4.7k Ω Resistor R14 package THT; tolerance ±5%; bands 4; resistance 4.7kΩ; pin spacing 400 mil
3 10k Ω Resistor R15, R16, R17 package THT; tolerance ±5%; bands 4; resistance 10kΩ; pin spacing 400 mil
1 1M Ω Resistor R18 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

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