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ColinP wrote: ↑Wed Oct 20, 2021 1:54 pm

huggermugger wrote: ↑Wed Oct 20, 2021 1:17 pm

ColinP wrote: ↑Wed Oct 20, 2021 1:02 pm A NAND gate with both inputs tied together is an invertor.

Cool, this works as well as the other. But can you explain how this patch creates the DC offset that martb''s solution requires?

You don't need a DC offset. It's just pure Boolean logic.

The NAND gate (like the NOR) gate has functional completeness. You can construct an entire computer with just NAND gates.

Cool, so inversion in the attenuverter is inverting around the 0V mark, while inversion via logic is inverting the signal in absolute terms.

ColinP wrote: ↑Wed Oct 20, 2021 1:46 pm Huggermugger is correct, martb's solution works. It's just that the NAND gate solution seems simpler to me because logic design was a hobby of mine back in the 1970's.

The NAND approach is simpler, just one module and voilà! On the other hand, the DC + attenuverter approach is easier on my brain, feels more 'hands-on' if you know what I mean. That said, I do a lot of generative-type patching, and it'd benefit me to get more comfortable with the logic module.

huggermugger wrote: ↑Wed Oct 20, 2021 3:21 pm Cool, so inversion in the attenuverter is inverting around the 0V mark, while inversion via logic is inverting the signal in absolute terms.

Absolute in Boolean algebraic terms, exactly.

Logical inversion (NOT) turns true into false and false into true.

A NAND gate performs Q = NOT ( A AND B )

If A and B are both the same then we can ignore B and it becomes simply..

Q = NOT A

And in the world of VM, false = zero volts and true = five volts.

huggermugger wrote: ↑Wed Oct 20, 2021 3:34 pm
The NAND approach is simpler, just one module and voilà! On the other hand, the DC + attenuverter approach is easier on my brain, feels more 'hands-on' if you know what I mean. That said, I do a lot of generative-type patching, and it'd benefit me to get more comfortable with the logic module.

Yeah, martb's solution is using real number algebra instead. It's calculating...

x = - ( gate - 5 )

So if gate = 0

x = - ( 0 - 5 ) = 5

And if gate = 5

x = - ( 5 - 5 ) = 0

Both approaches are equally valid. But if you are used to working with an analog computer (which is what a voltage controlled synthesizer effectively is) then the real number algebraic method makes more sense.

huggermugger wrote: ↑Wed Oct 20, 2021 3:21 pm Cool, so inversion in the attenuverter is inverting around the 0V mark, while inversion via logic is inverting the signal in absolute terms.

Inversion with the Attenuverter is the same as multiplying your signal with -1.

The Boolean Logic module interprets a signal as "high", if it is greater than or equal to 2.5 V, else it is "low". That's why NAND works for inverting gate signals.