The Synthrotek DLY is a PT2399 bucket-brigade style delay Eurorack module.  The PT2399 IC delivers lush analog-sounding tones (the IC is partially digital). The DLY is similar in tone to our ECHO Eurorack module, but its features make it unique in its own right.

Unlike the ECHO which always has a wet signal (i.e. the echo effect is always mixed in with the input), the DLY offers a true wet/dry Mix knob.  When the Mix knob is fully counter-clockwise, you get a dry signal. When it is fully clockwise, you get a fully wet signal.  This allows the user to incorporate this module into effects sends, etc. Also, the DLY allows for CV over Feedback and has an internal Feedback amount trimpot for precise adjustment.

Another added feature is the delay Rate range internal trimpot, which allows you to dial in the delay range of your choice. Adjust the trimmer and main Rate knob to dial in clean short slap-backs all the way to the extreme, chaotic sounds of an over-clocked PT2399 chip.



  • CV over DLY Rate
  • CV over Feedback
  • True wet/dry Mix
  • Feedback amount trimmer adjust
  • Rate range trimmer adjust
  • Rate/delay range: ~30ms – 1.13 seconds
  • Overclocked PT2399 “glitch” effects from fully turned Rate knob
  • 4HP
  • Depth: 1 13/16 inches (4.6cm)
  • Current draw: -12V = 10.1 mA;  +12V = 56mA





  1. Paul Whitt says:

    I just finished building the DLY. What a great kit! Super easy step by step instructions, well illustrated, pictures on the bill of materials, and it works flawlessly! Keep up the good work on the DIY kits.

  2. Steve Harmon says:

    Thanks for your support!
    -Zach at Synthrotek

  3. dorian says:

    would it be possible to modify the module to add insert connections to route external modules/FX into the delay line?

  4. Steve Harmon says:

    It would require modifications to the design itself but may be possible. I’d reccomend looking at the datasheet for the PT2399 to help you. Use the pinouts for the various inputs and outputs.

  5. charonme says:

    what do you mean by “the IC is partially digital”? there is an ADC, digital memory and DAC

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