Phase Lock Loop
  • Does anyone know how to make a phase lock loop in audulus?

  • Cool video, thanks for sharing! I've been looking back at PLLs, I built a synth based on torturing one about six years ago and I've just been dusting it off and trying to remember how it worked, it's nice to be reminded of some of these fundamentals now that I have some more practical electronics knowledge under my belt. No good answers right now, but it does seem like central bit is calculating the phase difference. Then if you have a frequency chirp in your reference and look at the rate of change of the phase difference, when the rate of change drops, you know you've found your sweet spot. At that point, maybe refocus the reference chirp and slow its rate. If there's a good way to make it an iterative process like that, it should iterate to the correct frequency. You'd get a nice series of chirps asymptoting to the target frequency, which would be a nicely complex sound.
  • I haven't watched the whole video, so he might recommend for or against this, but if you gain the heck out of your signals so they become digital and exclusive-or them, then average the output of that XOR, you could get this signal he's describing where higher numbers represent out of phase and lower numbers represent in phase, then you've got a phase detector, maybe?
    Screen Shot 2017-04-08 at 3.41.06 AM.png
    1766 x 1424 - 1M
  • Cool idea with the gain and clip to make square waves, I actually was just doing that to make an oscillator that morphs between wave shapes.

    I was messing around last night with sampling one waveform when the other crosses zero to calculate phase differential but just ended up making some weird bit-crushed dual oscillator. Interestingly if you get the two pitches close, the frequency of the sampled channel drops and you know you have found a sweet spot. But I am not sure how to model the feedback loop.

    There are of course several types of phase comparators so I look forward to exploring the XOR method as well.

    Also, I totally forgot about the mylarmelodies video on PLL. Check out the video around 5 minutes where he compares a complex wave table with it's square wave sub octave output.
    Screen Shot 2017-04-08 at 8.43.54 AM.png
    873 x 703 - 131K
    FM BUS Phase Chiptune.audulus
  • Ohh cool Doepfer module and video, those sounds really take me back, I should totally get or build some of those PLL modules. I love how crazy they get when they're struggling.