Sync Unit AC

What is it?

Sync Unit AC is a free solution for reliably syncing hardware instruments in software based music setups.

It uses generic audio ports instead of the latency and jitter plagued midi system to provide you with the best possible synchronization.

What do you need?

Requirements for Sync Unit AC:

  • any available audio output (mono)
  • a device that sync to line level audio
  • a recent audio unit or vst host application / DAW


  • Tape Sync (aka FSK Sync) compatible. (Roland MC-202, TR-707, Korg KMS-30, ..)
  • FSK double frequency: Böhm Digital Drums
  • 16th's (Korg Monotribe)
  • Rapid Pulse Sync (384 pulses per quarter note)

Get it now!


After installation, load the Audio Unit in your host software. The clock signal gets triggered by any note. When using FSK, you might have to configure your hardware device to respond to it.

Example: with Roland TR-707, you have to adjust the sync mode (SHIFT+SYNCMODE while in Track Play) until the display says "S-t". You have to press "play" on the 707 itself before activating the external FSK clock. Downside: when pressing stop on the 707, it will default to internal sync again.

The 16th pulse mode should work fine with Korg Monotribe (not tested yet, Monotribe isn't available here)

Rapid Pulse mode sends a 384 ppqn clock signal, so far this is just an experimental mode and probably has no use

Audio Interfaces known to work


Known issues

  • Looping cannot work accurately due to the note on/off trigger mechanism in Sync Unit. Use long notes instead.
  • Won't work with older host applications on OSX (e.g. Live 6).

Contact me

Suggestions, experiences, bug reports? Send me an email.

Follow me on twitter for updates:


I'd like to thank everyone who helped me out so far with contributions, advice and feedback. The people on KVR Audio, #musicdsp,, matrixsynth... Thank you all! Special thanks goes out to antto for fixing my n00b programming mistakes in the beginning and giving optimization tips.


The information contained within this document is subject to change and may contain errors. Sync Unit AC is free software and comes with no guarantee whatsoever. It sends clocking signals through your audio cables which should be safe. I cannot be held responsible for any damages caused by using Sync Unit AC.