CubuSynth Engine User manual

CubuSynth Engine - Build Guide PCB V1.1 May 2022

Page 1

Dual Complex VCO with wave shaping and modulation features

Build Guide

PCB V1.1 May 2022

Written and Illustrated by Ruben Sponar

CubuSynth Engine - Build Guide PCB V1.1 May 2022

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Introduction

This Build Guide is written for buiders with experience in soldering and assembling PCBs.

Due to the complexity of the build, the guide is focused on the steps that require special

care or techniques. Therefore, not every component value is described and listed as a

single step.

Tools Required

Soldering iron (+wire)

side-cutter

snipe nose plier

flat head screwdriver

Nut wrench / driver M6, M8, (M9/M10)

Digital Multimeter

Helping (third) hand / PCB holder

CubuSynth Engine - Build Guide PCB V1.1 May 2022

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MODS (optional but recommended)

Before you start, consider integrating these mods into your module. They will improve some of

its outputs significantly.

As the printing on the PCB still shows original resistor values, you should place these ones first to

minimize confusion.

WAVEFOLDER OUTPUTS:

R189, R190: change from 20k to 47K for higher Gain of wavefolder.

R236, R237: adjust for offset of wavefolder (usually 47k - 470k)

Leave them out until you Power up the finished module, then check the offset of the wavefolder

outputs on an oscilloscope with the wavefolding knobs on 100%.

If the Outputs are not centered around the 0V point, place 100k resistors and check again. Lower

Resistor values shift the output towards positive Voltages.

TRIANGLE OUTPUT:

R2, R3: change from 100k to 110k for offset of Triangle output, also improves sine roundness.

SINE OUTPUT:

R85, R92: change from 100k to 47k - 68k for better sine roundness.

Adjust R81, R96 to 220k –270k for higher amplitude

PULSE WAVE (VCO1):

C20: replace with wire (cutted resistor leg) for a straight Pulse on VCO1.

CubuSynth Engine - Build Guide PCB V1.1 May 2022

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BUILD GUIDE

STEP 1 (Switch PCB)

Take the small Switch adapter PCB and the 4 position slide switch. Place the switch on the side

that says SW3. It is recommended to use a helping hand to secure them together while soldering.

When soldered, cut the solder legs flush with the PCB to avoid shorting them later!

Then put it aside for later use.

STEP 2 (Main PCB)

Resistors

There is several ways to go, you might already have developed your own method to place

components and solder.

You can always select the resistors of the same value, place them, turn the board around and

solder in place. Trim the solder legs and move on to the next value.

Another method is to place all resistors and solder them from the top, without turning around

the board.

On the next page, you can find the list of resistors needed for the main PCB and a picture of all

resistors in place.

To help keep track of the already placed components, you can print the BOM and cross out the

parts you already soldered.

For the "10R/Bead" you can either use Ferrite Beads or 10R resistors.

CubuSynth Engine - Build Guide PCB V1.1 May 2022

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10R/Bead

L2,L1,L3

220R

R113

470R

R55,R44,R26,R18

820R

R56,R27,R101,R68,R37,R35

R214,R127,R126,R89,R88,R78,R67,R62,R50,R36,R16,R4,R95,R94,R83,R82,

R130,R129,R186

1k8

R46,R20

2k2

R196,R181

5k6

R54,R25

6k8

R195,R182,R61,R60

10k

R199,R194,R193,R192,R187,R184,R183,R178,R158,R112,R110,R64,R58,R121,

R120,R119,R118,R117,R116,R115

15k

R197,R180

20k

R205,R204,R203,R202,R201,R200,R175,R174,R173,R172,R171,R170,R66,R51,

R65,R57,R123,R109,R108,R107,R106,R105,R104,R103,R102,R190,R189,R188

24k

R49,R24

33k

R63,R59

47k

R198,R179,R166,R53,R30,R5,R142,R52,R237,R236

68k

R212,R145,R140

100k

R213,R146,R139,R92,R85,R77,R74,R73,R72,R71,R70,R69,R6,R111,R34,R29,

R7,R3,R2,R1,R122,R100,R75,R191

200k

R28,R8,R91,R90,R87,R86,R132,R96,R81

330k

R47,R22,R185

470k

R97,R93,R84

560k

R21,R15

R114,R98,R48,R43,R23,R17

1.5M

R45,R19

CubuSynth Engine - Build Guide PCB V1.1 May 2022

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STEP 3 (Main PCB)

Diodes

Before continuing with the build, check the time! You won't believe how much time has passed

while "only" soldering the resistors. Go to sleep if it's late or make a break. It is quite unlikely

that you will build the full module in just one day.

Identify the 1N400X* and 1N4148 diodes and put them in place. Orientation is Important! Make

sure the line on the diodes lines up with the stripe on the PCB silkscreen.

*can be any from 1N4001 to 4007 or 1N5819 (marked as 1N4007 on the PCB)

1N4001

D1,D2

1N4148

D3,D5,D4,D6,D7

STEP 4 (Main PCB)

ceramic capacitors

Find the ceramic capacitors

100pf is marked as "101"

1nf is marked as "102"

10nf is marked as "103"

100nf is marked as "104"

Orientation doesn't matter. Put them in place and bend the solder legs outwards, so they don't

fall when turning around the board.

Solder all ceramic capacitors in place. On the next page you can see how your PCB should look

by now.

100pf

C53,C52,C51,C46,C45,C44

C15,C11

10n

C22,C21,C9,C6

100n

C59,C57,C56,C55,C54,C40,C39,C38,C37,C36,C34,C27,C26,C23,C20,C17,C10,

C8,C2,C1

CubuSynth Engine - Build Guide PCB V1.1 May 2022

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CubuSynth Engine - Build Guide PCB V1.1 May 2022

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STEP 5 (Main PCB)

Transistors

Keep the 2N5457 for later, since it stands off further from the PCB. It is recommeded to start

with the 2N3904, then the 2N3906 due to the tight placement. Put them in place and make sure

the orientation is correct. The outline of the transistor has to match with the silkscreen on the

PCB. You can bend the 2 outer legs of each transistor, so they dont fall out when turning around

the board like shown below.

Lay the PCB down on a flat surface to make sure, the transistors are flush to the PCB.

The footprint for those is quite small, so stay focused and don't use too much solder to avoid

shorts.

Check your solder joints with a magnifier and/or multimeter when in doubt.

2N3904

Q16,Q15,Q14,Q7,Q6,Q5,Q4,Q2

2N3906

Q3,Q8,Q9,Q10,Q11,Q12,Q13,Q17

CubuSynth Engine - Build Guide PCB V1.1 May 2022

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STEP 6 (Main PCB)

IC sockets

Look for the dip-8, dip-14 and dip-16 sockets.

Orientation is important to know how to place the ICs later! The place for the notch is marked

on the PCB as "D shape" or with a dot on pin 1. In the picture below it is marked with a pink dot.

You can use tape to hold them in place, put the other PCB on top or bend 2 pins of each socket

inwards, so they don't fall when turning the board around. Then solder everything.

In this image, you can see the method of using the "control

PCB" to hold the IC sockets in place while turning around the

board.

IC Socket 16pin

IC Socket 14pin

IC Socket 8pin

CubuSynth Engine - Build Guide PCB V1.1 May 2022

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STEP 7 (Main PCB)

Polystyrene Capacitor

Place the Polystyrene (or other high quality) capacitors.

If it has a polarization, the marking on the capacitor should point towards the white line on the

PCB.

A normal ceramic cap will work as well, but since it may affect the stability of the VCO cores,

you should use high quality Plastic Film capacitors. Make sure, they are not taller than 10mm.

Here is different types of

polystyrene capacitors

STEP 8 (Main PCB)

2N5457 Transistor

Place and solder the 2N5457 N-channel JFET.

Make sure the outline of the transistor matches with the silkscreen on the PCB.

2N5457

1n Polystyrene

C13,C5

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