4046 PLL and Differential Amp question

[Synthaholic AKA sPEW]

On Wed, 12 Mar 1997 08:20:48 +0100 (MET), you wrote:

>> One of the failings of using a 4046 PLL as a frequency multiplier is
>> that it's output is square.  I have an idea to get at least one more
>> waveform out of it.
>
>Ok, why not using an external VCO together with the 4046 phase comparator.
>Somebody reported some time ago that this works pretty good, even
>if the ext. VCO is exponential. The waveforms may be a bit distorted, 
>due to the  permanent phase modulation.
Using an expo VCO will have a different overshoot characteristic than
a linear one, but I found the overshoot (and lag) to be useful in
generating interesting attack sounds.  Especially when the PLL output
is mixed with the original input, due to phase differences that occur
when the input signal changes frequency.  I'd say it will work, just
differently.

>
>Why not using a cheap linear integrator/comparator vco (tri,sqa),
>like the old Formant VCLFOs (also saw by chopping tri with sqa).
>Any experiences with such a cheap solution out there ?

This is probably viable, in fact, I believe that one of the phase
comparators is really just an XOR gate.  This comparator is the one
that will lock only to the fundamental of the input signal.  So if
that is what is desired, you don't even need the 4046 chip.

The reason for my original post, however, was that I already have 2
running modules that utilize the 4046, tracking another VCO, and I
wanted to get more waveforms out of it.

- Scott Gravenhorst (Synthaholic)     www.concentric.net/~chordman

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