#2750

Can somebody explain why the Maths XOR logic patch seen in this video: https://youtu.be/n_1bBTPBpxg?t=137 works?

It uses channel 1 and 3 as gate inputs, and channel 2 takes the inverted OR output. The XOR can be taken from the INV output. This doesn’t make sense to me though.
My understanding is that this patch is doing something like

-(A + B - Max(A, B))

with A being channel 1, B being channel 2, and -Max(A, B) being the inverted OR output. All with a - in front since we are taking the INV output.
Since OR is always positive and we are inverting with the attenuverter, channel 2 should never affect the OR output and would only be utilized in the SUM and INV outputs.

With A high and B low it seems like it would be the equivalent of subtracting A from itself which should give us 0.

-(1 + 0 - Max(1, 0))
-(1 - 1)
0

Same for B high and A low.

Obviously I must be misunderstanding something fundamental about the whole thing :frowning:
Any guidance would be appreciated!

1 Like
#2751

I get weird results if I use CH1 and CH3 for the two gate inputs. As in, I put 8V into CH3 and I get +10.7V out of OR.

But if I use CH1 and CH4 for the two inputs:

Ch1: 0V
Ch4: 0V
OR output: 0V
INV output: 0V

Ch1: +8V
Ch4: 0V
OR output: +8V
INV output: +2.4 V

Ch1: 0V
Ch4: +8V
OR output: +8V
INV output: +2.4V

Ch1: +8V
Ch4: +8V
OR output: +8V
INV output: -5.5V

If I mult +8V into CH1 and CH2, and set CH1 fully CW and CH2 fully CCW, I get:

+8V out of CH1
-10.4V out of CH2
-2.4V out of SUM
+2.4V out of INV

So that’s the trick, I guess :slight_smile:

#2752

Thanks for doing some tests! That’s pretty weird that you are getting more out of OR than what you are putting in. Did you use dummy cables to zero out channel 2?

Also, thinking a bit more on this, an analog XOR can be implemented by doing
Max(A, B) - Min(A, B)
AKA
(A OR B) - (A AND B)

Or as is actually being done in this patch:
-[ Min(CH1, CH3) - Max(CH1, CH3) ]
which is equivalent to
-Min(CH1, CH3) + Max(CH1, CH3)
and
Max(CH1, CH3) - MIN(CH1, CH3)
and
(CH1 OR CH3) - (CH1 AND CH3)

Summing CH1 and CH3 can act as an AND gate if the low voltage is negative.

  A  +  B
  -------
 +V +V +V
 +V 0V -V
 -V 0V +V
 -V -V -V

So the Maths patch does make sense but only if you have bipolar gates. Looking at the manual for pressure points it seems that it is 0V to +8V so I’m still confused though :frowning:

#2753

The Adventure Audio Merge would be a great option for you in this kind of setup: interfaces easily with line/instrument levels (guitar pedals, external synths, etc.) including a send-return setup. Plus, it will react to incoming audio (at modular or instrument/line levels) and generate various envelopes when triggered by the incoming audio - very flexible and pretty cheap as a kit! https://www.adventurepedals.com/eurorack/merge

1 Like
#2754

I’d like to get some more use out of my wavefolder (nls buchla style). Can anyone suggest some interesting patches to try? I have most bread & butter modules.

1 Like
#2755

mult a sequencer’s gate for an oscillator, and use that gate to strike an LPG, which then plucks the wavefolder with varying CV on each note played by the oscillator that runs through it.

5 Likes
#2756

Use it like an FM Aid. Take two saw triangle waves, call one the “modulator” and run it through a VCA, mix it with the “carrier” and feed the mix into the wavefolder.

4 Likes
#2757

Which logic modules are people using? I have an Erica Pico Logic but I’m not so into the scrolling through logic types with button presses, and I’d like more inputs.

2 Likes
#2758

I have the Ladik Bool2. The Bool3 has three inputs.

1 Like
#2759

For boolean logic, hard to top the Klavis Logica XT. It’s cheap, compact, and does loads of interesting stuff.

#2760

Do you have a link to a good explanation of logic modules?

Thanks!

1 Like
#2761

Sure. Note that there are two kinds of logic modules: ones that compare gates and ones that compare voltage levels. Some people refer to the former as digital or binary logic because everything they do pertains to creating two states (on or off), and they’re typically used to process gates and triggers, derive rhythms, and create logical patch programming (if this, then that). The latter are often called “analog logic” because they compare voltage levels (presumably one or two are fluctuating) and favor one over the other depending on which is higher or lower; these are used to process audio (or cv). Sitting between these two are comparators, which look at fluctuating voltages and generate binary states from them.

These are in no particular order—watching several of them should get you going.

7 Likes
#2762

I use omiindustriies’ Illyana! https://www.omiindustriies.com/illyana
The selectable logic section is great!

4 Likes
#2763

Fantastic! Thanks so much!

#2764

I have an ARC artificial neural network. It can be patced for many logic duties. Used to have the Doepfer dual logic which was also great.

2 Likes
#2765

I also was not a fan of needing to page through the various functions on the Pico Logic so I ended up removing it from my case. Right now the only module I have with explicit logic functions is a Mutable Kinks which includes a Min/AND and a Max/OR in addition to a few other utility functions. That, combined with a Maths, a WMD/SSF SPO, and a VCA lets allows me to patch up any logic function I need in a particular moment:
You can use pretty much any DC coupled VCA for AND. Just patch one gate to the CV input and another to the Signal Input. You should only get a high signal out when both inputs are high.

OR can be achieved with any module that provides DC coupled mixing. Just mix the gates and then you will get a high signal when either input is high.

You can get an XOR by inverting an AND and summing it with an OR.

You can do the voltage mirroring trick to get the NOT version of any of the above functions (NAND, NOR, XNOR). Just take a gate, invert it, and add a large enough offset to get a mirrored version. You can also run a gate into channel 4 of a Maths and take the EOC output to get the NOT version of that gate.

3 Likes
#2766

I wish these were still in production and that I wanted one enough to make space:

https://pittsburghmodular.com/logic-banks

2 Likes
#2767

When I was starting to find out about eurorack, I found this module very alluring. Never had one though.

#2768

Use a vca before the wavefolder. The input level makes a huge difference in most wavefolders so modulating the amplitude of your signal before it hits the wavefolder is a great way to find different timbres.

If you have a crossfader (or enough vca’s to patch one up) try using an envelope to crossfade between the original signal and the folded wave. This can give sounds reminiscent of a low pass filter sweep but with more variation. The overall sound of the Make Noise 0-Coast is largely based on this wavefolder and fundamental crossfade trick. Also try using a random source or sample and hold to modulate the fold amount for every new gate signal as a variation on the crossfader patch.

Instead of a sine or triange wave, try using a low pass filtered saw wave as your input source. Small adjustments to the frequency of the lpf will cause large changes in the wavefolded signal.

4 Likes
#2769

Apropos of nothing, just pointing out that “Little Modular” did an overview video of the new Klavis Quadigy Quad Programmable Envelope Generator a few weeks ago:

… and last night, I posted an in-depth video about the same module, but focusing entirely on using it as an expressive ADSR:

I presume the former video was paid commercial work; mine was definitely not. As usual, mine is obsessively (excessively?) detail-oriented. I still managed a few mistakes, which I’ve documented in the expanded video description on YouTube.

3 Likes