# Exponential control in custom unit?

Hi, is there a way in having an exponential control in the custom unit?
I would like to have the control of several parameters scaled differently than linear…

I’m not sure, but if you use a global chain to process the input and mix feedback from the output of that global chain into itself you can create exponential control from linear input signals; try negative and positive gain for logarithmic and exponential respectively. Then map the output of the global chain into your custom unit input.

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Ah yes, good idea. Although I try to avoid global chains, as I want to save what i‘m Building into a custom unit…
wasn‘t there a way to build Feedbacks just with custom units? Make a linear control, than put something into this control, and in the main custom unit feed it back itself?

Not really, well, unless you want to process the whole signal

All this will change at some point and things like this will become easier!

hello @odevices, any opportunity to see exponential behaviour in custom controls ?
given the complexity of the ecosystem it feels to me that this is becoming more and more of a necessity in my patches. thank you for any shared information.

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I feel like if you took a sample of an exponential curve you could use the sample scanner to turn a linear one into an exponential one.

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I just had an idea that I haven’t tested yet (don’t have a 301 set up currently).

Would it be possible to map 1/4 of a sine wave to approximate an exponential control? Set a sine oscillator to 0 Hz, set the bias of the phase control so that it’s at the lowest value (trough of the waveform) and then send your control into the phase modulation input, with gain scaled so that it scans through a quarter of the sine wave (from trough to zero-crossing). Of course you’ll need to scale and offset the output of the sine osc accordingly so it’s not from -1 to 0.

It won’t be a true exponential function but it should be close.

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it will probably work (as we know we can use sine oscillators as waveshapers) but… in the end it is the same as loading up a waveform in the sample scanner i think.
which is cool but a way to perfectly map a f (frequency) parameter of whatever unit to the custom controls of a custom unit would be killer

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Well, this feedback trick doesn’t seem to work much for me.
I’ve tried to use it to control the band volumes of the EQ3 that is inside a custom unit. The bands are natively controlled with an exponatial bipolar VCA…
I made a volume control for that custom unit that goes from 6 to -60 to mirror the display of the EQ3. Then I used it as a local. I managed to find the zero db point by calculating 1/60 = 0.01667 that I diled as gain control for the local.
I then tried to add the local inside itself and applied different values between 1 and -1 for gain control.

I already krashed the ER-301 twice with a feedback loop… I think it was because I went above and below those gain values.
Hope this makes sense…

Doing this with patch cords and pots is nice, but diling in the proper values at the right place is different. Then if you didn’t save proprely what you just did, you need to program this again after crashing the unit. More over I don’t know if the ER-301 doesn’t suffer from those repetitive crashes do to internal feedback loops…

It’s late at night and my math skills seem to abandon me…
Some help or some exponential fader unit would be nice for the math dub head like me.