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
1 group owner

__________________________________
Do you Yahoo!
SBC Yahoo! DSL - Now only $29.95 per month!
http://sbc.yahoo.com