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Patching Min and Max functions?
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author Patching Min and Max functions?
hinterlands303
How would one patch up a minimum or maximum function without a dedicated module (like the Intellijel uMod ii or Doepfer a-172 in euro)? I'm thinking of switching out my uMod ii but would miss the analog logic section of that module. Sum and Difference I understand but I can't get my head around patching Max/Min - is it something you can patch or do you really need a dedicated circuit? Thanks!
oberdada
Well, suppose your two signals are A and B. Subtract B from A and check if the difference is positive or negative. Use a switch to select A or B.

I haven't tried it though, but maybe you can get it working.
hinterlands303
oberdada wrote:
Well, suppose your two signals are A and B. Subtract B from A and check if the difference is positive or negative. Use a switch to select A or B.

I haven't tried it though, but maybe you can get it working.


That sounds like a patch to get the difference rather than minimum or maximum but maybe I'm missing something? How would the switch be used exactly?
AndreasD
Befaco's Rampage has such circuit.

Here are the schematics
https://www.befaco.org/docs/Rampage/Rampage_V1.3.2_Schematic.pdf
danfastlikeflan
hinterlands303 wrote:
oberdada wrote:
Well, suppose your two signals are A and B. Subtract B from A and check if the difference is positive or negative. Use a switch to select A or B.

I haven't tried it though, but maybe you can get it working.


That sounds like a patch to get the difference rather than minimum or maximum but maybe I'm missing something? How would the switch be used exactly?


If the difference is positive A is the max. If the difference is negative B is the max. The switch is so the output is always the max. Or swap it for min.
starthief
Use a comparator with two inputs (as opposed to one that compares against a fixed CV). Use that to drive the switch.
hinterlands303
danfastlikeflan wrote:
hinterlands303 wrote:
oberdada wrote:
Well, suppose your two signals are A and B. Subtract B from A and check if the difference is positive or negative. Use a switch to select A or B.

I haven't tried it though, but maybe you can get it working.


That sounds like a patch to get the difference rather than minimum or maximum but maybe I'm missing something? How would the switch be used exactly?


If the difference is positive A is the max. If the difference is negative B is the max. The switch is so the output is always the max. Or swap it for min.


Got it. This is starting to make sense to me now. I'll give it a go later and see how it works.
hinterlands303
starthief wrote:
Use a comparator with two inputs (as opposed to one that compares against a fixed CV). Use that to drive the switch.


Thanks - that seems like it wold work as well. Also I've got a comparator with two inputs so I can test it out. Sometimes this forum really comes through!
Navs
If it's function you use, I would just keep the uMod. It's not very big, is it? And it seems like a lot of patching for something that is achieved very elegantly with a handful of diodes hihi

Have a look at the diagram on the Doepfer page: http://doepfer.de/A172.htm

The min/max 'traces' the peak and trough of your inputs; it's two half-wave rectifiers and an OR combiner. I have a feeling switching would be more choppy. hmmm.....
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