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kylotan

Smooth high-cut sweep - possible?

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I've been trying to get a smooth low-pass/high-cut sweep effect, moving from 'very filtered' through to 'no filter', by adding a low pass block and assigning it to the expression pedal. Unfortunately, the parameter seems to move fairly linearly through the frequency range, so almost all the audible effect happens in the first 25% of the parameter's range as the frequency goes from 1KHz up to about 6KHz, and this makes it hard to control a smooth sweep with the foot pedal.

 

My understanding is that there's no way to change the curve of the expression pedal or the parameter mapping - is that correct?

 

If so, is there any practical workaround to get a smoother (logarithmic?) sweep between 1Khz and 22KHz/Off??

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The Q Filter in the Legacy category might come close to what you want. It has a lowpass mode and the response is smooth, but I don't know if it will go high enough for you...give it a try with the following settings, and vary Freq with the pedal. Because it's fairly high gain, you might need to put a Vol block in front of it and kick the signal down about -6 dB. Hope this helps.

 

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Great suggestion Craig! (This beats the old days of me moaning at you on the Sonar forums...)

 

You're right in that the filter doesn't go high enough for me - but I also added the Mix to the expression pedal, so it goes from the lowest frequency at 100% mix to the highest frequency at 0% mix. This means I still get a faster sweep than I could like, but it's less pronounced than just automating a low pass filter. Finally I added a level boost of 3dB at the lowest frequency to compensate for much of the signal being gone, again blending back to 0dB at the top so that the pedal fully level means the block has no effect.

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Cool! That sounds like a good workaround. It would be nice to have a 24 dB/octave-type ladder filter with an exponential sweep...but I'm not complaining. Helix rocks. 

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