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Davac 5 is new design of voice/SSB keyer for Tucnak. Although version 5 may appear to be a successor to version 4, is not true. It brings some advantages but also lacks some features.

To choose the version that best suits your requirements, please look at the table:

Davac versions comparsion
Davac 5 Davac 4
Size small bigger
Drivers required No Yes
Isolated No, use the USB isolator Yes
Band output No Yes
USB Micro-B or A male B
Soundcard Is the soundcard itself Uses PC soundcard
Audio cables Shorter Longer
Modulation relay Solid SPST Mechanical SPDT
Separated grounds No Yes


Davac 5 inside box with cables
Recommended assembly is stencil, paste and reflow oven


  • Simple assembly
  • All parts are SMD
  • Designed for SMD reflow
  • 3.5 jacks
  • 3D printed box
  • SMD LEDs + light guides on the top side
  • power supply from USB

Circuit diagram

Circuit diagram of Davac 5.1


  • R1, Y1, C2, C4 are not assembled in case of CM108B
  • Althrough preferred chip is the CM108B, is possible to assembly older CM108
  • The 93C46 is optional but recommended
  • The JP1 - Turns ON/OFF the audio mixer - please consult datasheet of the CM108B
  • I used LCBB-600 also instead of R9 and R16
  • R11 and R17 are for possible coarse attenuation

Connecting to the radio

  • MOD - Modulation output to the microphone input of radio
  • PTT - Push to talk output to switch Radio to the transmit (active low)
  • GND - One ground (ground plane on the bottom layer)
  • MIC - Modulation input from headset
  • BIAS - Microphone supply (from soundcard, not from radio)
  • CW - CW output to key to the radio
  • REC - Recording input to record band traffic

=Example for IC7400



  • PWR lights up - Device is powered from USB
  • PWR blinks - Soundcard is playing or recording
  • PTT - Push to talk is active (SSB and also CW)
  • CW - CW in the rhytm of Morse code
  • MIC - The SSR connects MIC to the MOD (off/disconnected if CQ is active)


  • CQ - Modulation level to the Transceiver
  • REC - Record level attenuator


Davac-5.1-gerber.zip Gerber files to order PCB at Elecrow or jlcpcb.com.


Davac-5.1-box.zip STL files for 3D printer.


  • Nozzle 0.4mm
  • No support, maybe brim in case of bad adhesion
  • Layer height - first 0.3mm, others 0.2mm
  • PETG or PLA

Light guides are made from transparent PETG filament.


Davac51-bom.csv Bill of material for tme.eu .

(not including cables)

Set USB string to EEPROM

Only if the 93C46 is installed. From menu Setup, CW keying, Davac5 options.

EEPROM edit in Tucnak