D Pots

[frets]

Hey Guys,
Hope you’re all being safe and your families are safe.

So I buy these Bourns Pots, 16 of them, thinking they were A logs given the pot number ended in a 254A2. But oh no, they arrive and they’re D pots. D250’s. I figure they are for digital applications but I’m hoping one in the fellowship can explain these to me. They look like a regular ol pot. Thanks.

[thetragichero]

oooh you got good'ns
from my understanding D taper is a closet approximation of logarithmic taper than A, as all pots are made up of linear segments approximating a logarithmic curve (i hear my high school calculus teacher's voice calling them "piecewise linear")

so no need to 'fret'

[thetragichero]

stolen from a diysb post that came up from a 'bingle' search

audio taper (aka A-taper): Usually 15% resistance at the 50% rotation point.

log taper (aka D-taper): Often used as an audio taper since its 50% rotation point has 10% resistance.

[JohnH]

Hi frets
How about checking it out with a meter? If you set it to mid turn as carefully as possible, then you could measure resistance from middle lug to each outer lug to see if you get a ratio of 10% to 90%

[frets]

Hi Trag and John,
Thanks for your help. I will hook them up to a meter and check their resistance across the sweep. I am glad to know they are of extreme tolerance. I just can’t believe in all my years of guitar making and fixing that I’ve never encountered such.

[thetragichero]

if these are pots I'm thinking of they also give some "resistance" as you turn em, of which i am a huge fan. i was a bit of a wild man in my younger years so pots that wouldn't change their settings by simply looking at them the wrong way was a must
although I've also primarily between the type of neanderthal who just puts everything on 10 and leaves it there

[thetragichero]

pulled this outta something. gonna be the volume pot for my current single p90 build

[frets]

Trag,
That’s exactly what they look like with the D250k written above the lugs.
BTW - that’s quite the beauty shot of the pot. It looks like you’re standing on a mountain precipice looking down over a granite outcropping. Ha!

[frets]

Update to D Pots:

I took John’s and Trag’s suggestions and did a test of two Bourns Pots - a Bourns A250k vs a Bourns D250k, with regard to
overall taper sensitivity.

I went through a random selection of my A pots and then tested the 16 D pots that I ordered in error, to find two of each that matched in terms of similar “k’s”-  with the A250k measuring in at A248k and the Type D at D249k. I measured at increments that I “felt” represented an incremental turn of the pot; i.e., position 1,2,3...so on). I did five trials of the incremental pot turns, computed the average of each pot; and, created the following chart.



As one can garner, the Type D Pot exhibited a higher degree of incremental sensitivity than its cohort variable (Type A Pot).  However, one may ask, “is this difference significant?”

Statistically, the answer is “No.”  The two variables exhibit variances that are not significantly different.  I put the data into my Stat Program and did a simple Analysis of Variance Test between the two regarding incremental differences (ANOVA).  It resulted in 7 of 8 tests of the taper differences between Type A and Type D pots that were not significantly different.

I then found a similar graph to mine on the web conducted by a Dude overseas that resulted in a similar graphic trend between Type A and Type D pots.




Whew, so there is a difference as you can see; however, the difference is not statistically different.  Boo Hoo! 

Now do I think you’ll hear the differences between Type A and Type D pots.  Probably not. Ha !

[JohnH]

Thanks frets that's great. I have learnt something today and its still only 6am! I had not appreciated the difference A to D before.

One thing that occurs to me is that if you are adding treble bleed circuits, which tend to 'flatten the curve', or make the taper less steep, a D pot would be a good thing to start with.

[frets]

Thanks John, I appreciate your recommendation to pursue it. I’m interested in the treble bleed aspect you referred to. Basically the same measurement comparison as the one I did using treble bled A and D pots? Just making sure.