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EuroPi CVecorder - An open-source 6-bank, 6-channel CV recorder and playback module

CVecorder ("Sveecorder")

author: Nik Ansell (github.com/gamecat69)

date: 2022-04-13

labels: sequencer, CV, performance

CVecorder is a 6 bank, 6 channel CV recording and playback program that runs on the EuroPi from Allen-Synthesis. It can be used to control the CV of any module in a really fine-grained way, rather than spending time creating CV patterns with sequencers, envelopes or LFOs, you simply record the exact CV pattern you want and have this played back into your modules.

Also, because CVecorder has 6 banks you can record 6 different variations of 6 channels of CV, then smoothly change between them during a performance without skipping a beat!

Note, due to limitations in the Raspberry Pi pico (the hardware running behind the EuroPi), only positive CV can be recorded and played back.

Demo video: https://youtu.be/Crj0P7pr2YA

Controls and Display

Operating Diagram

Getting Started

The following sections provide instructions for recording and playing back CV using CVecorder.

Initial Connections

  1. Connect a 50% duty cycle gate input to the Digital input
  2. Connect a CV source to the analogue input (0 to +5V works best)
  3. Connect each output (1 to 6) to modules you want to send CV to

Recording and Playing back CV

CVecorder records CV using the following format:

  • Each CV channel records a total of 64 CV values (samples).
  • Two CV samples are recorded for each received gate. One sample is captured on the rising edge, another on the falling edge.
  • Each CV channel is looped with every 32nd gate into the Digital input.
  • Each CV sample is captured with a resolution of 0 - 9.99, providing a resolution of 1000 potential CV values to record.
  • Each CV channel relates directly to each output. CV channel 1 sends the recorded CV to output 1, CV channel 2 to output 2 and so on.
  • There are 6 banks of 6 CV channels, allowing you to record 6 variations of CV recordings in each bank and move smoothly between them during a performance.

To record and playback CV:

  1. Send a 50% duty cycle gate to the Digital input, this will automatically start the CVecorder. You will see this on the display on the bottom left-hand side.
  2. Select the required bank using knob 1
  3. Select the required channel using button 2
  4. Press button 1 to queue CV recording to the selected bank:channel. You will see indicator at the bottom of the screen change to '. .' , CV recording will start at the beginning of the CV channel. 'REC' will be displayed when recording has started.
  5. At the end of the channel, the recorded CV is output from the corresponding output.
  6. Select the next required CV channel using button 2, then repeat step 4.
  7. Once you have everything the way you want it on bank 1, select the next bank using knob 1 and record your next set of 6 CV channels to the next bank.
  8. During your performance, you can move smoothly between each CV bank using knob 1. This allows you to switch between 6 variations of CV to all 6 outputs.

Saving CV between power cycles

Every time you record a new CV channel, CV is automatically saved to local storage on the Raspberry Pi pico. This means that you can power off your module at any time (other than during the recording of a channel) and it will always be available when you power back up.

To overwrite saved CV simply record over it. However, if you would prefer to clear an entire bank or all banks use button 2 - see 'Clearing banks' for more info.

Clearing banks and channels

If you want to update the CV recorded into a channel, simply record over it. To clear a bank, repeat this process for all channels in the bank. However, if you would rather clear a channel completely hit record and send no CV into the channel during the recording period.

Patching ideas

Painting quantized melodies

This patch allows you to paint melodies using a CV source like a joystick. CV is recorded and played back by the CVecorder, which is quantized to scale and sent to a VCO.

  1. Connect a 50% duty cycle gate to the Digital input
  2. Connect a CV source to the analogue input (0 to +5V works best) for example a joystick

If your quantizer has a trigger input:

  1. Mult / Divide the gate input and connect to the quantizer trigger input. This will sample CV from the CVecorder each time it receives a gate
  2. Connect CVecorder output 1 to the quantizer input
  3. Connect the quantizer output to a VCO
  4. Play around with subtle movements on your CV controller and hear the melodies come out of your VCO!

If your quantizer has no trigger input:

  1. Mult / Divide the gate input and connect to a sample and hold trigger/clock input
  2. Connect CVecorder output 1 to a sample and hold CV input
  3. Connect the sample and hold output the quantizer input
  4. Connect the quantizer output to a VCO

Extreme FX control

This patch provides super-granular control of FX modules, allowing you to control the value of each FX parameter up to two times with each clock cycle. Doing this can create both smooth and whacky FX changes.

  1. Connect a 50% duty cycle gate to the Digital input
  2. Connect a CV source to the analogue input (0 to +5V works best) for example a joystick
  3. Connect each of the outputs to parameters on your FX module
  4. Play around with different combinations of CV across the different channels to have fine-grained control of your FX CV parameters

Creating percussion variations

This patch allows you to add interesting variations to your percussion.

  1. Connect a 50% duty cycle gate to the Digital input
  2. Connect a CV source to the analogue input (0 to +5V works best) for example a joystick
  3. Connect each of the outputs to parameters on your percussion modules, for example connect to inputs that control pitch, accents, timbre or sample.
  4. Play around with different combinations - if it sounds good stick with it!