Doepfer

I thought I would point out that in the analog realm, the Absolute 
Value function is really a full-wave rectifier (or AM detecter). If 
you input an audio signal, and smooth out the ripple by patching the 
absolute value to a slew limiter, the patch becomes an envelope 
follower.

Joe

--- In Doepfer_a100@yahoogroups.com, "Joe Buechler" <buechlerjoe@t...> 
wrote:
> Hi Bakis
> > by the way,the two bottom rows of jacks in the a166
> > are not placebo!they are two trigger inverters.
> > bakis.
> 
> Right you are! I haven't looked at the front panel layout since 
> the A166 went into production. The earlier front panel illustration 
on 
> the Doepfer web site used to have a row of output jacks below the 
NOT 
> or inverter function, for logical false (or low). these were just 
> dummy jacks - zero volts - as far as I can tell. Not sure where that 
> space went to, I think the triple output jacks for the logic 
> functions have been added also.
> 
> Anyway, my mistake, not keeping up with the news.
> 
> Joe
> 
> > 
> > 
> > --- Joe Buechler <buechlerjoe@t...> wrote:
> > > I thought I'd describe how do a min/max function and
> > > other comparison 
> > > logic using attenuation/offset and the A150 VC
> > > switch.
> > > 
> > > The most simple single-input comparison is to test
> > > whether a voltage 
> > > is positive or negative, i.e. X > 0. 
> > > 
> > > Patch a CV source or other fixed voltage to an A138a
> > > mixer channel, 
> > > turn all the mixer knobs fully clockwise, and patch
> > > the mixer output 
> > > to the A150's CV input jack. Adjust the CV source
> > > until the A150 is 
> > > right at the switching threshold (both LEDs dimly
> > > lit).
> > > 
> > > Now patch your unknown voltage, lets call it X, to a
> > > second channel on 
> > > the mixer. If X is positive, the switch will close,
> > > and if X is 
> > > negative, the switch will open. That completes the X
> > > > 0 patch.
> > > 
> > > You can use this to create an Absolute Value
> > > function:
> > > ABS(X) = if X > 0 then X else -X
> > > Use the voltage inverter module to patch X and -X to
> > > the A150's I/O1 
> > > and I/O2 jacks. The O/I output is the Absolute Value
> > > function.
> > > 
> > > You could feed random LFOs or other combined signals
> > > to the ABS 
> > > function to get different variations of these
> > > signals. Feed the output 
> > > to the A156 if you like, it's always a positive
> > > voltage.
> > > 
> > > To do a two input comparison, or compare two unknown
> > > voltages with 
> > > each other, just patch the second voltage Y through
> > > the voltage 
> > > inverter to a third channel on the mixer. Now you're
> > > testing 
> > > X - Y > 0 which is the same thing as X > Y.
> > > 
> > > Now you can create the Min and Max functions:
> > > Max(X,Y) = if X > Y then X else Y
> > > Min(X,Y) = if X > Y then Y else X
> > > Just patch the X and Y voltages to the A150's I/O1
> > > and I/O2 jacks. The 
> > > O/I output jack will be the Min or Max function.
> > > 
> > > There's uses for an X > Y comparison other than the
> > > Min/Max functions. 
> > > For example, you could use a sample and hold to
> > > compare each 
> > > successive note CV to the previous not, and have
> > > different sounds for 
> > > ascending and descending musical passages.
> > > 
> > > You can also create keyboard zones with a variable
> > > split point, 
> > > something digital synths can't usually do. This is
> > > useful, for 
> > > example, in a guitar patch, where the transition
> > > from wound-string to 
> > > flat-string sounds isn't at a fixed note, like it is
> > > on a piano.
> > > 
> > > To create Dieter's three-input Min/Max function,
> > > it's a simple matter 
> > > to cascade two-input Min/Max functions in tandem:
> > > Max(X,Y,Z) = Max(Max(X,Y),Z) (same for Min)
> > > 
> > > Since the VC Switch and Voltage Inverter are dual
> > > modules, all you 
> > > need is a second mixer to create the second Min/Max
> > > function.
> > > 
> > > Give these a try, it'll give you an idea whether the
> > > proposed Min/Max 
> > > module will be useful to you. Personally, I would
> > > rather have a module 
> > > with just the comparison logic, it would be more
> > > versatile. In fact, I 
> > > think it was a big mistake to leave out comparison
> > > logic on the A166 
> > > Boolean Logic module, which could have been included
> > > instead of those 
> > > stupid placebo jacks on the bottom.
> > > 
> > > Joe
> > > 
> > > 
> > 
> > 
> > =====
> > synthfreak(parallel worlds)
> > athens-greece
> > [Doepfer_a100] group owner
> > 
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