#33 ARP 2600 suffers denormal with zero inputs to filter

admin
closed-duplicate
7
2009-03-07
2009-03-04
No

If the filter inputs are all dropped down towards zero the engine tends towards 50% or higher CPU load. Probable cause is denormals on the low signal level so some form of prevention needs to be applied.

Discussion

  • Nick Copeland

    Nick Copeland - 2009-03-04

    The problem, reported by Colin Fletcher with a good description of the reproduction, is easy to demonstrate. An initial fix has been sent out where -84dB of noise is injected into the filter whenever the net input signal levels drops below -84dB. The S/N ratio at full mix to no mix is then actually better than -84dB since multiple inputs can be mixed, it resolves the denormals and additionally the noise ensures that the filter will 'self' oscillate, not previously possible - it always required an input signal to oscillate. OK, now it always has one so it is not really self oscillation but the net effect is.....

     
  • Nick Copeland

    Nick Copeland - 2009-03-05

    This should be closed and tracked as a duplicate of bug id 2665269 which requests denormal be addressed for all the filters rather than just for the ARP 2600.

     
  • Nick Copeland

    Nick Copeland - 2009-03-06
    • status: open --> pending-duplicate
     
  • Nick Copeland

    Nick Copeland - 2009-03-07

    Closed

     
  • Nick Copeland

    Nick Copeland - 2009-03-07
    • status: pending-duplicate --> closed-duplicate
     

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