Hi Timothy

> > So we are there where I always end up: I want a PLL-Module ;-)
> I think I missed out on some understanding here - what do you want to do
> with a PLL, and what features would it need (I'm intrigued!)

A delay (whether BBD or real digital) is controlled by a clock, not by a
CV. So for voltage control of the delaytime you need a vc-clock. This is
nothing else than a VCO with square output, but in a quite high frequency
range (usually between 20kHz to 160 kHz).

It would be no problem to make the base frequency of a VCO that high, but
then we have a very expensive Module (the Highspeed VCO) which can be used
only for the delay. I would like it much more to use a standard VCO and
feed the Pulse out into a module that can multiply the frequency. This
module is the so called PLL in combination with an divider.

Now what is a PLL
A PLL compares the signals of two VCOs. If the edge of the one VCO comes
later than the other, an offset voltage is derived from that time
difference. The voltage is sent to the other VCO so that both VCOs run with
the same frequency.

=== is audio
--- is CV

Controlling-VCO1=>==\
PLL compares and creates offsetCV-->--+
VCO2==+====>==/ |
^ | |
| | |
--------<-------------------------------------------+
|
+===============> Audio out

This looks quite boring, since the Audio out will have the same frequency
as the Controlling VCO, so what for The trick comes in with the divider:

1kHz
Controlling-VCO1========>==\
|
64kHz 1:64 PLL compares and creates offsetCV-->--+
VCO2==+=>=Divider=>==/ |
^ | |
| | |
--------<------------------------------------------<------+
|
+===============> Audio out
64kHz

Now we cheat the PLL. We let him compare the Signal of the Controlling VCO
with a signal that is derived from the divider out; so the VCO2 will sound
at a much higher frequency.


This output signal can be used now for clocking the delays BBD or digital
memory reading circuit. You may think of many nice games you can play with
the offset CV - games you never could play with a VC-Delay.

So: I want a PLL :-)

Florian
--
Florian Anwander |ConSol* HP-Support
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