Steady Slew LFO

[jh]

>Something I've wanted to see for years is an LFO that has adjustable slew
>rate  instead of speed. Changing the depth would simultaneously increase or
>decrease the LFO fequency so the slew rate would remain the same. This
>would be especially nice for time delay effects that cause pitch bending,
>because the amout of bend would remain constant (with linear waveforms),
>regardless of the "depth" of modulation.
>
>Should make for some really interesting knob twiddling. Just imagine being
>able to crank up the frequency range of a flanger without changing the slew
>rate. Then, if you ran it through the exponential input...
>
>Has anybody done this? I've never seen it.

Haven't done this, but it should be easy. Asuming you have the garden
variety integrator / schmitt trigger (triangle / square) LFO, normally
you make the integrator time constant adjustable, and you have an output 
level pot. Now discard the output level pot and make the hysteresis of
the schmitt tigger adjustable instead ...
But think of some lower limit, as zero hysteresis coresponds to "infinite"
frequency (though with zero amplitude). Nevertheless, might be quite
interesing within a certain range. Just start with making one of the resistors
in the positive feedback (of the schmitt trigger) variable.

JH.