Generate audio sync signal for PO-33 K.O!

Software
1

I would like to generate an audio signal for syncing the Teenage Engineering PO-33 K.O! Its requirements are simple: send a single pulse, of around 20 ms width, in tempo.

I tried with a plain square wave generator, sending a C1 note on, with the minimum duration possible (0.1 step in the sequencer). It seems fine, but the resulting signal changes when I change the BPM. At 60 BPM, the signal starts high and keep the pulse for the correct amount of time. But when I set it to 120 BPM, it is inverted. Moreover, the synths that I’ve tried don’t start high on every note (some depend on the earlier state).

So, the question is: does anyone know a way to generate a signal like this? :

PO-33 sync signal
PO-33 sync signal1188Ă—199 6.31 KB

I don’t mind writing an LV2/native engine, if needed… :slight_smile:

2

You can configure a GPO output to pulse in sync. Maybe that will work for you.

You could record an audio pulse and load it into zynsampler then use a sequence pattern to trigger it.

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3

By “GPO”, you mean a General Purpose Oscillator? :sweat_smile: What is a GPO?

Yes, I already tried that, but in my first try I couldn’t mange to make it work, and I thought that it was overkill, so I desisted. I’ll give it another try.

Thanks @riban! :slight_smile:

4

Eureka! I’ve managed to make it work, using the ZynSampler (thanks @riban). These are the details, for future reference.

  • I’ve recorded a single tick from the OP itself, and put it into a WAV file, attached below. I’ve added two CUE points inside to mark the interesting region. You can download it to an USB drive, or copy it inside your Zynthian (I’ve called the file po-sync-tick-cue.wav).
  • To make it work, create a ZynSampler chain, and load the po-sync-tick-cue.wav. Set the loop mode to one-shot.
  • Create a new 16 step pattern on that chain, and add a C4 note on every odd step (1, 3, 5…). The expected sync signal is 2PPQN.
  • Configure the “Main chain” > “Audio Out” to be on “Output 2” only. This is the price you need to pay, audio will be mono from Zynthian out…
  • Configure the “ZynSampler chain” > “Audio Out” to be on “Output 1” only, not in “Main mixbus”.

And there you have! Connect the Zynthian audio output to your PO, with a TRRS cable, and choose SY4 as sync mode. Select a pattern in your PO and press play. Then, on your Zynthian, trigger the sync pattern you created earlier. You can adjust your tempo, and of course, play other instruments as well. :slight_smile:

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