Differernce between A and D taper?

[jpm83]

I just "salvaged" a couple of 50k D taper pots from radio cassette recorder. I have understood that D is some sor of audio taper, but what kind.

Janne

[John Lyons]

I don't think I've heard or a "D" taper.
Put a knob on the shaft and mount it in a box or cardboard so it wont slip.
Mark the rotations %.
Measure the resistance at 25%, 50%, 75%, and 100% (or smaller increments) and make a graph of the taper curve.
Then you will know what the taper is.

John

[Dai H.]

I've read of them and one source describes it as an accentuated audio taper

http://part.freelab.jp/image/VRcave.gif

[John Lyons]

Whaddaya know...?
Cool little graph there. Thanks Dai.

john

[Dai H.]

sure, no problem. I just happened to have that link because I was searching for info on the (apparently slightly unusual) "D" taper to see if I could find some connection between that and old wah pot tapers.

[jpm83]

Thanks for the replies. So it's even more logarithmic than A taper.

Janne

[d95err]

Just remember that different manufacturers use different ways to label their pots. Sometimes "A" is for Audio, sometimes its A(linear) B(log) and C(rev log). To know the taper of a pot, you need to read the datasheet from the manufacturer or measure it (as suggested above).

[Michael Weidenauer]

Maybe there are exeptions, but normally American and Japanese manufacturers use b for linear and a for log tapers, European companies use a for linear and b for log.

[Dai H.]

the other little bit of info I found here:

http://www.rane.com/par-p.html

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.

and as far as the wah pot stuff this is what I was looking at:

http://www003.upp.so-net.ne.jp/kazuhee/wahpots.htm

[pawleep]

will a D taper (dournes D250K) work ok for a guitar or bass volume and/or tone?

[thermionix]

yes

[buck1107]

I was looking for a replacement mini potentiometer "D500K" and looked everywhere, but couldn't locate any D tapers.
However, when I contacted Bourns, they knew what it was. 
Apparently, they call the "D taper" an "A2 taper," and it is 10% output at 50% rotation, so just about 5 or 10% less output than the standard audio taper (or "A").

[jfrabat]

Well, learned something today.  Had never heard of D taper before reading this!

[Rob Strand]

buck1107's post got it.

D = log  taper ;     10%               (of total resistance at mid position)
A = audio taper;   15% to 20% (of total resistance at mid position)

In the old days there were a lot of D's.   Perhaps around the late 70's  A's started to become the norm.
Both were always available.