Changing where a tone pot kicks in.

[skiraly017]

I'll apologize up front for probably not being able to get my question across clearly.

I've been messing with a BMP style tone stack. I have the values where I want them but I don't like the feel of the pot. What should be mid point tonally is about about 2 to 3 o'clock in the pot rotation. How would I go about making that a more even spread (12 o'clock being tonally and mechanically the same or close to the same)?

I hope that was understandable. Thanks in advance.

[GibsonGM]

Good question.  You can read at GeoFX about tapering resistors (article= "the secret life of pots").
Set up your tone stack how you like it, remove the pot without moving the setting, measure resistance leg 1 to wiper, leg 2 to wiper.  Then calculate how to taper that value to be in the middle of the pot's range.  Probably a pain in the @ss.

Or do what I do...carefully remove the knob, and put the marker line upwards (centered) where you like the tone to be.  Then it looks balanced, and you'll probably never deviate far from that setting, anyway ;o) 

[Dragonfly]

get duncans tone stack calculator

plug in the values you are using

try different pot values and tapers, noting how the frequency curve is effected

[Mark Hammer]

It,s probably easier than you think.  It's a 100k pot, right?  Chances are it's not actually 100k, but rather something less.  A value in the high 80's or low 90's is not uncommon.  So stick a fixed resistor in series with the side that seems to dominate.  You say that you have to set it at 2-3:00 to have a balanced tone?  That means you need to turn it more treble-wise than you anticipated, right?  Okay, try sticking a 10k resistor in series with the bass-side input to the tone pot.  That ought to move your "midpoint" a little more to the left.

[skiraly017]

Thanks for the ideas.

I have been using the TSC to figure things out. Ultimately I am tyring to make a mid-hump EQ for the BMP. I have found the values I want to use but now I've noticed something else. There's an apparent volume boost at the extreme sides of the pot rotation. Not a big one but if I start on the bass side and rotate clockwise, the volume appears to decrease slightly around 10 o'clock, level off until 2 o'clock and then increase slightly from there on. I'm thinking/guessing this isn't so much a volume drop as it is an increasing/decreasing of certain frequencies (the old turning the bass and treble up on the cheesey car stereo to get more apparent volume). I have not thoroughly searched the forum yet to see if anyone has already done this so if it's been posted before I apologize. If anyone has thoughts about mid-boosting the BMP tone section or the volume perception issue, please feel free to add your two cents. Thanks.

[squidsquad]

I hope you've peeked into Jack Orman's lab notebook pages....mucho info there about tone controls & variations of the BMP stack.

[skiraly017]

I hope you've peeked into Jack Orman's lab notebook pages....mucho info there about tone controls & variations of the BMP stack.

Why I just placed the order this morning and I'm awaiting my email from Mr. Orman as we speak!