logarithmic potis possible?

Design Concepts
1

hi again,

many answers to my desgin questions I found already in the archive, but not this one:

I have a lot of logarithmic potis around (from the days where I wanted to build analog mixers..–))). I understand that for MB64 a linear curve is preferred, but is there a way to “scale” the values so i can use my logarihmic ones?

thanks,

kap.

2

Hi kap,

In short: log pots won’t work. Sorry!

3

stryd,

thanks anyway, better to know it from the start…

kap.

4

sell them and buy linear pots

5

wisefire:

like your name suggests, wise advice, thanks.

6

I have not yet “been inside” the MB64 code, so please take this with caution.

There is code in the MBMixer that will convert a 7 bit linear value into an 8 bit Log value, and also code to convert 8 bit Log curve back to _AN APPROXIMATION_ of a linear curve.

The resolution is a bit grainy, especially at the low end of travel. It is sized only for 8 bit to 8 bit conversions, if you need something different you’d have to remake the look-up-table.

To find it, get the archive here:

http://www.midibox.org/dokuwiki/lib/exe/fetch.php?id=midiboxmixersoftware&cache=cache&media=mbmixerv1.zip

(If that link doesn’t work, it’s in the WIKI at the end of the software page for the MBMixer)

from the zip file get “logbyte.inc” and look inside for a function called “AntiLog” and it’s data table, alogtable.

Having said all that, it’s not the “right” way to go. Your MB64 will be different from everyone elses, and if it doesn’t work “just right”, you’ll be on your own. I agree that using the right parts is the best way to go.

Good Luck,

LyleHaze

7

lyle,

thanks, I agree that such a mod would stray away from the mainstream too much… I have a lot to learn already, so I will invest in new pots to get rid of even more problems to think about..—)))))

kap.