Doepfer

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

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
> 
> __________________________________________________
> Do you Yahoo!?
> Yahoo! Tax Center - File online, calculators, forms, and more
> http://tax.yahoo.com

hi joe,
very...complicated,indeed....
right,but then you would need too many modules for
doing what you could do with only one module.so,this
module,too,has a purpose.
by the way,the two bottom rows of jacks in the a166
are not placebo!they are two trigger inverters.
bakis.


--- Joe Buechler <buechlerjoe@toadmail.com> 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

__________________________________________________
Do you Yahoo!?
Yahoo! Tax Center - File online, calculators, forms, and more
http://tax.yahoo.com

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
> > 
> > __________________________________________________
> > Do you Yahoo!?
> > Yahoo! Tax Center - File online, calculators, forms, and more
> > http://tax.yahoo.com