Dying battery simulator (variable voltage pedal) aka JHS Volture

[airbud]

I've been hoping for a volture build!! this is awesome, well done.

 

[simonvangogh]

How do I make one for my home made fuzzface from a kit with a center positive connection?

 

[Feral Feline]

... I also would've loved the Age control to be an actual potentiometer, but I could not find a reasonably priced and appropriately sized 100 ohm potentiometer.​

...

I've been looking around Aliexpress and places like it, and found various 100Ω pots.
However, none advertised reveal their shaft diameter, or height etc. Sparse info given.
Prices aren't too bad, from just under a buck on up, but ordering one pot + shipping just to see if it's garbage or not...



So I thought I'd fire up the 1728 Parallel Resistor Calculator and see what I could come up with whatever is available at Tayda.

I found a 500Ω Linear-Taper Pot that's PCB-mounted, round shaft of a diameter 6.35mm — for 59¢.

Perfect, but...
OUT OF STOCK

However, given the existing layout, something with solder-lugs might be better, anyway:
500 OHM LINEAR TAPER POTENTIOMETER WITH SOLDER LUGS
ALPHA 17 MM | SHAFT DIA: 6.00MM | B500 OHM LINEAR l SOLDER LUGS | T18 SPLINE SHAFT 17mm (10.5mm+6.5mm) |

Splined, but it'll do, in stock and more arriving mid-summer — and at 50¢.


Now to fire up that 1728-calc linked above and see how close we can get to 100Ω with a parallel resistor strapped across lugs 1&3.
(All resistors below in Ohms, 1/4w metal-film available at Tayda)
500Ω
+ R? =
100 = 83.333
102 = 84.718
110 = 90.164
120 = 96.774
130 = 103.17
150 = 115.38


So, depending on tolerance drift of the pot and of the resistor, it would seem 120Ω or 130Ω resistor in parallel with the 500Ω-pot will get you close to the desired 100Ω.







Then there's a Fender amp part (needs a shaft):
"100 ohm Chassis-Mount Hum Balance Potentiometer"

$$$