Active Boost/Cut Pot Taper

[ncusack]

Hi,

I'm wondering if anyone here has experience modifying the following active boost/cut circuit to improve the pots taper.



I'm currently using a 50K Linear pot and all the gain is bunched up in the last 10% of the rotation. I remember reading somewhere that an S taper pot should be used for this circuit so I'm curious if the two resistors I added marked with ? could simulate this. If so does anyone know a good ratio of values that could make this work?

[Eddododo]

Blend (MN) pot could do it, I believe.

[lietuvis]

MN blend is dual potentiometer, I suggest to go with W tapper which I think is log antilog single, the one is used for tubescreamer tone control, something like this http://www.taydaelectronics.com/potentiometer-variable-resistors/rotary-potentiometer/w-taper.html

[ncusack]

I understand there are specialty pots out there for this application but is there a way to modify a standard linear pot for a similar taper? here?

[armdnrdy]

Here is a pot taper calculator:

http://www.diystompboxes.com/analogalchemy/emh/emh.html

I've used it to improve the taper of the Rate pot in the Mutron Flanger clone that I worked on.

The original Mutron used a custom modified log taper pot.

Use the calculator and experiment.

[merlinb]

Are you sure you haven't simply set the break frequency too low, so you don't notice the changes that much? A linear pot is usually OK for a control like that, as it gives a uniform sweep in decibels.

[ncusack]

Hey Merlin,

It is entirely possible I have set the break too low as I'm new to this type of active control. In the schematic above I currently have 100nF across the pot connecting to 2.2K on either side with a 47nF on the wiper that connects to two 470K down to the inverting input. This is giving me about 15dB Boost/Cut at 85Hz . Again the majority of that boost is happening in the last bit of the pot rotation. If someone could point me to any documentation on how to design this properly it would be a great help.