#70 Pro 52 Pulse abnormalities

Andrew C

Playing around the middle range of the keyboard results in the prophet 52 to literally 'screech' as the two pulse oscillatros clash.

The attached memory should make it more obvious.


  • Andrew C

    Andrew C - 2010-04-21
  • Nick Copeland

    Nick Copeland - 2010-04-21

    The issue is the Sync flag, the oscillators are not clashing but you are trying to sync one osc to another where the following osc is at a lower frequency. There are a couple of things here:

    1. If you want to sync then the source should really be at a lower freq than the dest.
    As they tend to the same frequency and especially where the following osc is at a lower frequency you will get a bad signal: one of the oscillators never completes a cycle before it is reset.

    2. You will get better results if not syncing pulse.

    3. I think the bristol code is actually wrong here and am searching for sources to confirm: I have OscA as the following oscillator, it should be OscB following.
    If OscB follows then the FineTune gives some interesting harmonic changes. This does not really affect your problem: if the leading osc is higher than the frequency of the following osc you will get odd results.

    Regards, nick.

  • Nick Copeland

    Nick Copeland - 2010-04-21

    So, OscA following OscB appears to be correct according to the owners manual.

    I will have a look into the Prophet sync though. The bitone oscillators do this differently - an oscillator can generate a sync output signal as well as accept a sync input. In this implementation the sync output signal is a perfect square wave and when used to drive the sync input of another such bitone oscillator the sync is easier to derive. Perhaps I need to push this back into the prophet DCO too.

    Regards, nick.


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