AtoVproject cDVCA - DIY kit

Written By Arthur Gibert

Introduction

Thank you very much for purchasing one of our DIY kits.

This manual is aimed at guiding you step by step through the process of assembling an AtoVproject cDVCA. If you have any questions or if you are missing a part please contact us at Support@atovproject.de.

Required tools and materials

First, to successfully build this DIY kit, you will need a few tools and materials.

  • Soldering Iron

    • No need for a high-end iron. Temperature control is preferable to avoid burning the flux in your solder and leaving residues. With prolonged use, higher than necessary temperatures will damage your soldering iron tip. We recommend the TS-100 or TS-80 digital soldering irons for hobbist use. As professional tools we use the JBC CD-2BQF with a range of tips.

  • Solder

    • We recommend lead-free solder as it is gentler on the environment and your health.

    • We have tested a lot of solder over the years and we now recommend the Stannol Kristall 611 TSC - Sn96.5Ag3Cu0.5. For a good all-rounder we would recommend 0.7 mm diameter solder. This is a truly no-clean solder; leaving very little residue, a great finish and with odorless flux fumes. (They do not sponsor us, we just very much like their product and we use them in our production line -Bonus- Their customer service is great!)

  • Side cutter

    • We like flush cutters but side cutters will also work. Any cheap cutters will do but higher quality tools will last longer. Knipex is our go to in the workshop

  • Multimeter

    • This is important to have for testing and troubleshooting. Use a multimeter with continuity mode. Our reliable and inexpensive multimeter recommendation is the ANENG AN8009. If you are in the market for a professional tool, we use the Brymen BM867s (or BM869s if you need temperature probing)

  • Flux (optional but recommended)

    • Liquid no-clean flux is sufficient for such a build. In our workshop we use Stannol 32-10/i no-clean flux pen.

  • Oscilloscope (optional, could be a good investment if you want to get serious into electronics)

    • We use the Siglent SDS1104X-E which has been fulfilling our needs until now. Unfortunately, we don't have experience with cheaper oscilloscopes. But I would recommend getting a digital one instead of analog as they have measuring tools, memory, take snapshots, can decode digital signals etc… Good oscilloscopes are expensive and this one is a great budget option.

Secondly, to build this kit you need to know how to solder. If you want to learn how to solder, our recommendation is to purchase an inexpensive DIY kit from your local electronics shop. This will allow you to train yourself at soldering and build confidence before building a more complex kit.

If you need a small refresh on soldering techniques, here is a tutorial https://www.youtube.com/watch?v=Qps9woUGkvI

Opening the kit

The kit should contain:

  • 1 x panel

  • 1 x PCB populated with SMD components

  • 1 x bag of parts

  • 4 x knobs

  • 1 x Eurorack power cable

Open the bag cDVCA Parts. Make sure this bag contains the following.

  • 4 x potentiometer + nuts

  • 6 x jacks + nuts

  • 2 x trimmer

  • 2 x LEDs

  • 1 x 2*5 pin header

Check if the kit is complete as well the state of the provided parts. We inspect inspect everything in the workshop but it's possible that damages occur during shipping. If there are any obvious defect on any of the parts provided please contact us, we will provide a replacement.

Part 1 - Back Side

There is only one part to solder on the back of the PCB, the 2*5 pin header used a Eurorack power connector.

Put the connector in its location and solder one pin. I would recommend soldering a pin in a corner of the connector. The central pins are connected to ground and because of the internal ground plane take a more heat to solder.

When this is done, check if the connector is flush against the PCBs. If this is not the case. Reheat the pin you previously soldered and push the connector down with your finger. Remove the iron and let the solder resolidify.

When everything looks good, proceed then to solder the rest of the pins.

Part 2 - Front Side

Start by placing the 4 potentiometers. These are “snap in” they will therefore snap in place and hold on the PCB. Make sure they are pushed all the way against the PCB.

Once done, you can proceed to place the rest of the components, the 6 jacks, the 2 trimmers and the two LED. Be careful the LEDs are polarized. The + (long leg) goes to the bottom.

Place the front panel and use a nut to secure it in place. Then place some tape on the LED holes (painters tape works great because it is designed not to leave traces). Push the LEDs into their holes and against the tape. This will hold them in place.

Then you flip the module around and solder the components. Little noteworthy details, near the A of the Atovproject logo, are two pins very close to each other. These are both connected to ground, it is not a problem if they are shorted.

Calibration

Calibration PWM

Method 1 - With a Multimeter in duty cycle mode

  1. Power the module using a Eurorack power supply.

  2. Set the frequency potentiometer in its center position.

  3. Connect your black probe to the GND point on the back of the PCB.

  4. Connect your red probe to the TP2 point on the back of the PCB.

  5. Adjust the D% trimmer until the duty cycle is 50%.

Methode 2 - With an oscilloscope

  1. Power the module using a Eurorack power supply.

  2. Set the frequency potentiometer in its center position.

  3. Connect your ground to the GND point on the back of the PCB.

  4. Connect your measuring probe to the TP2 point on the back of the PCB.

  5. Adjust the D% trimmer until the duty cycle is 50%

Methode 3 - With an audio interface and an oscilloscope application

  1. Power the module using a Eurorack power supply.

  2. Set the frequency potentiometer in its center position.

  3. Set the VCA and VCF potentiometer fully clockwise.

  4. Set the Drive potentiometer full counter clockwise.

  5. Plug the output of the cDVCA into your audio interface input

  6. Fire up your oscilloscope application. I would recommend the MedalProduction MOscilloscope, mostly because it’s free very easy to use and come in a bundle with a lot of very useful plugins.

  7. Monitor the waveform and adjust the D% trimmer until the duty cycle is 50%.

Calibration V/Oct

Important Notes:

The cDVCA is not designed to be an accurate oscillator, the tracking will not be perfect over the whole range and it is not temperature compensated so it will drift overtime.

Different tools can be use to measure the frequency of the module

  • Multimeter in frequency mode

  • Tuner

  • Computer with audio interface and tuner application, I would recommend the MedalProduction MOscilloscope again because it is faster than a traditional tuner (i.e. like the Mtune).

  • Oscilloscope

Procedure:

  1. Power the module using a Eurorack power supply. Leave it connected for 2-3 minutes for everything to warm up and be stable.

  2. Set the Freq, VCA and VCF fully clockwise and Drive Fully counter clockwise.

    Optional step to save time:

    1. Set the frequency potentiometer fully counter clockwise.

    2. Measure the Voltage at TP1

    3. Adjust the V/Oct trimmer until you measure 2.56V

  3. Connect the output of the module into a Tuner/Frequency counter/Oscilloscope

  4. Set up equipment to generate 1V and 3V. This can be in multiple ways:

    1. Using 2 offset generators (16n, Maths etc…), set one to send 1V and the other to send 3V to be able to switch rapidly

    2. Using a CV keyboard, this should be C1 (1V) and C3 (3V), check with a multimeter until you find the key generating these voltages.

  5. Send 3V (MIDI to CV or a keyboard) a into the FREQ and tune the cDVCA to C5 (523 Hz)

  6. Send 1V (MIDI to CV or a keyboard) into the FREQ adjust the trimmer to tune the cDVCA to C3 (130.8 Hz)

  7. Go back to step 5 until the tuning is accurate in 10 cents (between 130.04 and 131.55) (more accurate tracking can be achieved, this is the objective we aim at in the manufacturing process)

Testing

Important Notes:

Don’t overthink it, if it sounds good that most likely means that everything is fine. The testing can be done ear

  1. Set the potentiometer in the following positions:

    • FREQ CW

    • DRIVE CCW

    • VCA CW

    • VCF CW

  2. Decrease the frequency potentiometer, you should hear a square wave, the lowest frequency should be around 6hz so in the high LFO range.

  3. Set the FREQ potentiometer back to CW

  4. Send a signal from an oscillator into the input (either sine, triangle or sawtooth)

  5. The sound coming out of the VCA should be similar to the input signal (maybe with a little bit of distortion as the cDVCA is not designed to be clean). The LEDs should light up with the when the signal feed in.

  6. Set back the FREQ to CW, Set the DRIVE to CW, the signal wave should be clipping and turn into a square wave at CW

  7. Leave DRIVE to CW

  8. VCF potentiometer applies a low pass to the signal.

  9. VCA potentiometer should control the amplitude of the signal.

Any issues? Contact us at Support@atovproject.de

Part 4 - Final assembly

When everything works well, then you can finally install the remaining jack and pot nuts. Put the push on knobs onto the potentiometers. Finally, use the included washers to mount your new module to avoid any marks from the mounting screws.

Congratulations! Your AtoVproject cDVCA is now complete and fully functional.

Arthur Gibert
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