Doepfer

That sounds interesting to me although I don't completey grasap it, but the
wobbling and inaccuracy in this case could be more advatageous as an effect
than a pure VCO it seems to me... when did this module come up on the
agenda? I didn't even know it was something Doepfer had in mind....


----- Original Message ----- 
From: "Bakis Sirros" <synth_freak_2000@yahoo.com>
To: "Doepfer_a100 group" <doepfer_a100@yahoogroups.com>
Sent: Thursday, June 26, 2003 6:06 PM
Subject: [Doepfer_a100] a brief explanation about the uses of a PLL
VCO.(from doepfer.)


> dieter says:
> "a PLL and it's application is not very easy to
> understand. I will try to write an explanation and
> publish it on our web site as soon as we publish the
> preliminary page for the PLL module (no A-100 number
> so far).
> Here is a simplified explanation: A PLL is a linear
> rectangle VCO with a frequency comparator that
> compares the frequency of the internal PLL-VCO with an
> external frequency (master frequency) - e.g. the
> rectangle output of  "normal" A-100 VCO - and makes
> the the internal VCO frequency equal to the external
> frequency. Or better said: it tries to adjust the
> internal frequency so that it becomes equal to the
> external frequency. The problem is the frequency
> comparator - even called phase comparator - that
> generates a kind of a correction voltage that becomes
> zero if both frequencies are identical. Different
> versions with different advantages/disadvantages of
> frequency comparators are available. Some types of
> comparators e.g. will "lock" even at multiples of the
> frequencies. Another problem is the time that is
> necessary until the PLL-VCO is adjusted. It will
> always take some time until the new frequency of the
> PLL-VCO is reached (similar to portamento). The time
> constant of the internal low pass filter (not an audio
> low pass but a low pass/slew limiter for the
> correction CV) defines the time until the new
> frequency is reached. But this time has not to be too
> short otherwise the frequency of the PLL-VCO will
> "wobble" around the master frequency. These
> "disadvantages" lead to additional musical
> applications like portamento effects or wobbling
> frequencies according to the type of frequency
> comparator and time constant of the PLL low pass
> filter.
> Another application is frequency multiplication in
> combination with an external frequency divider. For
> this the output of the PLL-VCO is processed through a
> frequency divider (e.g. A-160, A-161, A-163) before it
> is fed to the PLL frequency comparator. In this case
> the frequency of the PLL-VCO will be a multiple of the
> master frequency. E.g if the the A-163 is used and
> adjusted to dividing factor 5 the frequency of the
> PLL-VCO will be 5 times the frequency of the master
> VCO. Consequently frequency division (A-163) leads to
> frequency multiplication with the PLL circuit. In
> combination with the PLL low pass frequency several
> effects can be realized (frequency multiplication with
> portamento or wobbling). The frequency multiplication
> can even be used to drive a graphic VCO. If your
> graphic VCO e.g. has 8 steps (e.g. A-155) and you use
> a frequency divider with factor 8 in the PLL feedback
> the output of the graphic VCO has the same frequency
> as the master VCO. Another application is the
> generation of pseudo-harmonics (not real harmonics as
> only rectangle waves are available).
>
> I hope this explanation will help and not cause more
> confusion. I know that the PLL is not very easy to
> understand.
> Best wishes
> Dieter Doepfer"
>
>
>
> INTERESTING???????OF COURSE,YES!
> bakis.
>
>
>
>
> =====
> synthfreak(parallel worlds)
> athens-greece
> [Doepfer_a100] group owner
>
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