No subject

To make sure, I tested using a sine wave and the instability occurs at the same Q as with PWM or saw.  

Higher f values restrict the range of Q.  A combination of too high f with too high Q causes instability (nasty).  Limiting f to a reasonable maximum seems to mitigate.

Thanks for everyone's help, so far, so good.

-- ScottG

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-- Scott Gravenhorst
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