Ebay 75mm Slide pots - Interesting Taper

[Buriedcode]

I was looking at slide pots for a prototype, so I bought up a few different models for sizing, to see which ones would fit in the enclosure I was going to use.

Whilst there's generally 45mm travel and 60mm travel, aliexpress and ebay have lots of those 75mm ones (60mm travel, but slimmer), often stereo, that are quite low profile  - like the bourns PTA6043 - and was a better fit than the larger ones like Taiwan Alpha RA6020F

Examples of the cheap clones are here:

https://www.amazon.co.uk/DollaTek-Potentiometer-Double-Linear-Electronic/dp/B081JNQ7MM

I bought a pack of 5 from a random ebay seller, and one from a known "good" seller, that was mounted on a breakout board for use with Arduino/Rpi etc..

They're the perfect size for my prototype, but the taper is odd.  It seems to be a "W" taper, despite all being labeled as B103 - which is usually 10k linear.  The value goes from 1k to 9k (10% to 90%) between 25 and 75% of travel, which to me at least, looks like a classic W taper used in graphic EQ's.   As a quick and dirty test, I used an Arduino to read the wipers with the top and bottom hooked to 5V/GND, and roughly moved it 6mm at a time to get 9 readings, and reading both tracks.

All 7 pots I have use this taper, which is annoying since it can't be used for linear control apps - even if I used a lookup table to correct its less than ideal.  But it seems these are perfect for making graphic EQ's like the classic MXR 6 band EQ. 

So this is just a FYI post in case others wanted to use these for control inputs and got funky results.

[strawberry]

they make interesting components but can spoil all fun with just one thing

tin plated = silver plated

something strange with China. everything must be unbelievably cheap and unbelievable low quality and must look like 1milion 

[electr_peter]

Linear pots are unusual in audio applications. Sliders intended to be used with motor control have two potentiometers inside - linear for position and non-linear for audio.