How to make your reverse taper pots... roughly.

[sean k]

I'm doing a skyripper which calls for a dual 1MB set of pots and the place I get pots from only has duals up to 100k. So I remember that taking pots apart ain't that hard so I buy a dual 100k and a coupla 1MB's.
As a result of this, I made the set of pots I want, I have a coupla spare of the fibreglass boards with tags that are the pot tracks and then I remember somewhere a mention that sanding the track changes the overall resistance. So I did that and low and behold the resistance  increases as you sand off more of the track. Therefore the lower the resistance the thicker the track.

That means that if you want a 100k reverse taper log pot you start with a 10kB track and sand down the end you want to have greater resistance on. I just quickly did it with 400 wet and dry but would suggest 600 or higher as a starting point and carefully sand from the beginning into the track and gradually decrease the length along the track you sand, measuring resistance as you go.

Another possible, and the first that occured to me was a pot wired with earth to the centre lug and each outer lug connected to a set of diodes to the outgoing signal rail. Then sand a trough accross the mid point in the track so the centre lug essentially is lifted or goes open at mid rotation. With some dicking about, I'd start with a 10kB, you could then have what is a tunable centre off switch on the diodes. Some careful sanding on the edges of the centre off trough would allow a nice progression into the diodes coming on.

This all comes from a pedal, which was also a Gagan device, which had a dual gang pot which needed a cut accross a track so that at the end of rotation the pots connection to ground was lifted. There was even pictures about how to take the pots apart. It was the Decade from 2005 and there may be that it's still out there and with the links to taking the pots apart.

[John Lyons]

Joe would be proud of you!
I was going to mention that he did/does some of this in his work but you found that out yourself.
Looking forward to seeing your Skyripper build!

john

[sean k]

Thanks John, in taking apart the pots I figured out the manufacturers could make dicking about with pots a simple task and then at the shop I asked about making suggestions and the first thing the guy said was your not supposed to pull them apart. I can see their point as sellers but I think we're entering a new world these days and suppliers who see that having options that decrease waste available now will come out ahead in the years to come.

All it would require in this context is that instead of hammering off the end of the shaft to hold the centre lugs rotating wiper they could put on one of those spring washers that presses on. Then the whole pot, sans carbon track, could be bagged and shipped in alot less space and sold with your choice of track. Nobodies losing, except maybe the people who can't be bothered putting the thing together, less shipping space is taken up and people are learning to do for themselves again which, in the world to come, I think is going to be a valid part of keeping western civilisation going and not going back to fuedalism.

Whatever, eh!, I know, but butterflies swishing wings can create hurricanes!