Wah pot mapping

[snarblinge]

I have searched and searched but cannot find someones carefull wah pot map that was pictured somewhere.

I don't have a Wah to map myself and am looking to use a microcontroller to simulate a wah pot, would like the curve a little more accurate than I can figure from the graphs kicking around.

does anyone have such a thing?

standard dunlop style is fine.

thanks

[CynicalMan]

This site has a graph of the Dunlop Hot Potz II:
http://www.area51tubeaudiodesigns.com/pot_taper_charts.htm


It just looks like a standard log pot that only works from 0-50% of the rotation. Most pots have a 10% or 20% tolerance, so you shouldn't need the data to be that accurate, just tweak the taper to your taste.

[snarblinge]

thanks, i'll work from that...

if only it were my taste.

[snarblinge]

so what percentage of this would a standard wah enclosure travel.

i understand the treadle doesn't cover the full sweep. hence the flat bit. but do I use 55% or 60%, i'm just trying to avoid a whole lot of reworking on code, thanks.

[joegagan]

the hotpotz2 is the same taper as the hotpotz1 which matches thomas organ's taper from at least the early 70s.

i lost some data on an SMD card, i had a whole shitload of measured pots graphed out.



if you can make sense of the above, have at it. this radial method preceded my later rig.
i use a straight stick attached to the wah treadle in a cardboard 30" extension rig. the wah's travel is amplified using the stick so that the entire travel is spread out to 28 measure points in an 8 " spread.
this method tells me exactly what the pots is doing in actual usage.

hotpotz1 and 2 have a rapid rise ( moreso than standard log), and a large blank spot on the treble side. i assume this was designed to give better mfg control, less problems getting full treble while still giving the switch room to switch. some people like this 'kink', rapid sweep, others don't. the quest for icar tapers comes from people who want a more gradual ramp. when measured in the actual pedal, icar looks almost linear.

even more linear in actual use is the 25k pots used in the venerable dearmond shell used by maestro for the boomerang. it is almost a straight line.
it is a modified rev log. normal wah pots have a real hard time in the boomerang as the rotation is opposite , the kink is not only unwelcome, but in the wrong spot.
the boomer has approximately a 1/4" longer throw than a standard crybaby or vox, depending on the rubbers used. there were some vox castings back in the 60s that had a wider throw, i am told. i just built a boomer in a crybaby shell and the travel on the log pot i used just barely made it ( achieving full bass all the way to full treble), even with cutting the rubbers down to little nibs.

inspired by paul marossy a long time ago, i modded a CB shell to try and get a wider sweep.

had to extend the straight gear as well


anyway, congrats on your digitization venture. i know there are some other people working behind the scenes to achieve this, but the more the merrier. if you can pull it off, it will be wahnda-ful. shoot me an email at joegagan*atgeemail if you want to pick my brain some more.

so, back to the hotpotz taper. you are correct, a normal wah hardly makes it to 155-170 degrees of the pot's travel. if you work really hard at it, you can get 180. that is why icar often gets complaints in that you have to sacrifice either some low or some high. the hotpotz definitely gets the whole sweep because the sweep is all bunched into less than 180 degrees. see above radial chart.

[snarblinge]

Thanks Joe, it was your drawing I was looking for. Saw it a while back in some other thread. 

Will let you know how this all ends up..

[new]

My test result

[joegagan]

found one of the charts. the pots were measured in the actual pedal, as described above. kinda  cool to see them mapped out.

after testing hundreds of pots, i could generalize things.






above chart, boomerang wahs scaled up 3X to compare map, 30k (marked 25k) pots.

[snarblinge]

Wow Joe, that is beyond awesome.

[phaseman]

Hi everyone,
I did some tests last year when I wanted to swap my very cheap way pot for traine-led-ldr type of control and after all experiments I ended up by buying the hotpotz in the store...
The biggest problem was how to make the pot (one, or both halfs) go from 0 ohms to 100 kohms by turning the shaft for less then 90 degrees....

I did some measurment, here is the preview:


Here are the xls, ods, and pdf files:
http://dl.dropbox.com/u/51704507/WAH%20pot%20graf/gcb95%20POThot%20values-II.xls
http://dl.dropbox.com/u/51704507/WAH%20pot%20graf/gcb95%20POThot%20values-II.ods
http://dl.dropbox.com/u/51704507/WAH%20pot%20graf/gcb95%20POThot%20values-II.pdf


Regards,
Marko

[joegagan]

awesome, thanks for posting that!

[snarblinge]

double awesome. thanks