implementing frequency modulation in a delay path?


    May 18 2010 | 2:04 pm
    hello everyone
    im pretty new to all this stuff but i thought i'd give it a go as i have always wanted to build my own VSTs, etc. Anyway, i'm trying my hand at emulating (or trying to) a tape delay and am having difficulty in implementing frequency modulation into the feedback loop and i have tried and tried and all that happens is the audio drops out and everything is unhappy until i disconnect it.
    has anyone tried this or know what it is im doing wrong?
    thanks
    Hugo

    • May 18 2010 | 2:31 pm
      Sounds like you have an "illegal" feedback loop. Try using tapin~ to tapout~ or send~ and receive~ in your feedback loop. Send~ and receive~ introduces a delay of one signal vector which allows the audio signal to be fed back to itself.
    • May 18 2010 | 2:48 pm
      its really odd - i am only using send~ and receive~ and all other effects (dist; amp mod; filt) work fine. it is just the freq mod that makes it bad. in all honesty, i am not entirely sure that i have connected the patch into the loop correctly which is why i think it is giving me problems. it is also odd that when i directly connect the freq mod patch to the tapout~ inlet, the feedback loop is modulated but i obviously loose control of the delay parameters which i don't want to do. i am confused about the freq mod because i have never had to do it like this, i have implemented it into synthesisers but i don't really know how to use it here. sorry - i am, like i have said, very new to this...
    • May 18 2010 | 2:54 pm
      Can you post your patch so we can give you some concrete feedback? ;)
    • May 18 2010 | 2:58 pm
      aha-let me just have a tidy up and i'll sort something out. any other pointers would be welcome too ;)
    • May 18 2010 | 3:23 pm
      right - here is the delay line
    • May 18 2010 | 3:24 pm
      as you can see i have left the freqmod disconnected
    • May 18 2010 | 3:25 pm
      and here is the freq mod patch
    • May 18 2010 | 3:27 pm
      this is definitely wrong... i know it is. i just don't really understand how it needs to be implemented. to be fair - i used to do a bit of MSP a few years ago but am rusty as they come.
    • May 18 2010 | 3:28 pm
      woops, need to actually post the damn thing.
    • May 18 2010 | 4:26 pm
      You probably mixed up frequency modulation and ring modulation. For FM you modulate an oscillator's frequency (or it's phase aka phase modulation).
      For Ring-Modulation you simply multiply one signal with another (typically a sine).
      In your patch you add "frequency" to your modulating signal and add that to the original signal. So "frequency" will end up as a nasty DC-Offset.
    • May 20 2010 | 9:11 am
      he invented DC modulation^^  
      btw, you could use a signal to cotrol tapout (try putting a [line~] before it) that gives you more options. and with tapout, always make sure, you do not feed too short arguments for the buffer ( can crash or crackle.