Another interesting implementation (especially for guitarists) is from
an article by Harry Bissell:
http://go.cadwire.net/?3572,3,1It uses three peak detectors which are continuously reset. I did a
digital implementation as a Mac Audio Unit, and the responsiveness for
guitar is quite nice.
I don't have the wavefolder, but I patched up a rudimentary EF by
sending an amplified guitar signal to both inputs of the 110 ring mod
followed by an 820. Lot's of ripple but still fun.
Tomy
On Saturday, July 19, 2003, at 07:53 PM, groovyshaman@... wrote:
> Paul Haneberg wrote:
>> It seems to me I read something once about using multiple FWRs as
>> frequency doublers in envelope followers. This is supposed to improve
>> the response time. I may have read this somewhere in ElectroNotes,
>> I'm
>> not sure. I'm out of town at the present time and unable to verify
>> the
>> source. It might be interesting to have outputs from multiple FWRs
>> on a
>> module such as this.
>
> Yes, this is my understanding. And yes, Electronotes #60, #86, #88 &
> #89 -
> good memory! There is a trade off when determining the time constant
> of the
> filter between being able to detect snappy envelopes and reducing the
> amount
> of voltage ripple on the detected envelope for lower frequencies.
> Obviously
> fast envelopes at low frequencies is the biggest problem.
>
> So by adding say two additional FWR sections, this would quadruple the
> frequency of the signal (in theory) thereby allowing the low-pass
> filter
> cutoff frequency to be increased, which in turn improves the speed
> (response
> time) of the envelope detection. From what I understand however, FWR
> does
> not work properly for sine waves (or other predominantly even-harmonic
> waveforms), as the subsequent waveforms are not symmetrical about the
> x axis
> and do not frequency double. An AC-coupled peak-correction circuit
> can be
> used in conjunction with each FWR section, to add in the appropriate
> amt of
> offset voltage to the FWR section to make up for the non-symmetry in
> the
> waveform. (I think I've got that right :)
>
> Anyway, I have yet another crazy feature that may be nice. I think I
> remember reading about it somewhere, the MAM filter or something? Have
> three envelope follower sections, each tracking a separate frequency
> range,
> say low, mid and high. Then the envelope output of each of those
> could be
> sent to the three inputs on the OMS-410 filter companion module. Woah
> -
> sounds like fun!
>
> One more thought (like beads of water on the forehead, eh? :) .. until
> a
> MOTM equivalent is available, if one has a Wavefolder and a MOTM-820, a
> simple envelope follower could be patched up.
>
> Cheers,
> George
>
>
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