Pot designations

[bsco]

Have a question about pot designations at the risk of sounding stupid or whatever.....I am after running into a few situations where I have had to order say a 250k15A pot and received a 250K30A pot...(wrong pot was sent in by mistake)..... and was told (by the manufacturer or supplier), that there is practically no difference......so what exactly is the difference.......as the 15A was used as a gain control and the 30A was used for a bass control..apparently it is the same taper....does the numbers 15 and 30 relate to degrees of rotation for a given change in resistance such as 15 degrees of rotation to have a resistance change of 20% or 30 degrees of rotation for a certain percentage (doesn't have to always be 20%..it could be any percentage...)... of a change in resistance??? And if so, is the percentage of rotation the same within the same family of pots or is this something that I am blindly assuming??? Trying to get a handle on what these 15A, 30A, 5C, etc...designations mean....like I said..at the risk of sounding stupid.....
Thanks,
Bernie

[Enzo]

A linear pot will be at half resistance at the mid point. An audio taper will not be at the half resistance point.

250k10 means at mid point 10% of resistance, 250k30 means 30%.

In practical terms they are very similar. Your knob positions will be a little different. If I didn't have the one, I'd use the other.

[bsco]

Thanks Enzo...very much appreciated...
Cheers,
Bernie

[Chuck H]

Just to add...

I'm glad for the different log pots. If everyone thought "Hey, it's the same exact function, with the same exact range, so it's OK that the setting will be different." that would be great. But it just doesn't go down like that. As a designer I need to consider the aesthetic of "knob position". Example... There are A LOT of posts here about guys that are all bent about flabby overdrive with their old Fender's or similar clones. The most common complaint is that they need to turn the bass knob below "2" or the amp is farty and flabby. The perception being that they can't get enough bass out of their amp if it's clipping. In fact, once the bass knob is advanced to the point of flab, it should be backed off until the flab goes away and THAT is the maximum bass the amp can produce. Advancing the bass knob further only clips the LF more. Which is flabby but NOT more bass. This REALLY bothers some people that simply won't "get it" and they simply want to see the bass knob at a more moderate setting to assure them that they're doing all they can to get "fat" overdrive tones. Enter the 250k10A pot. I build an amp with a Fender type topology that isn't unlike a Trainwreck idea. That is, it's a Fender topology with an extra gain stage POST tonestack. There is no post preamp EQ like the Marshall topology. So when clipping the EQ is really just a distortion character adjustment. My amp is capable of high gain, but also a lot more classic type tones than the TW design. Which means it's capable of more bass if you dial it in. I didn't want anyone complaining about the bass knob setting being too low when the amp is clipping. So I use an A10 pot for the bass control. The nominal bass knob setting when my amp is clipping hard with a bridge humbucker is five-ish with good definition. If I used a typical 30% taper pot the setting would be about two. And everyone would complain. So, I am very glad for the alternative offerings. And...

I hope your customer doesn't mind the need to use a different setting. You might be surprised.

[bsco]

Thanks Chuck for that info...but what I was asking was what the difference in the designations in the tapers were..I do realize that different pots with different tapers installed in different places will have different effects....and like you stated, the customer might be surprised....and I have already done that...but I was just wondering what the different degrees of tapers meant....and how I could relate them into something that I could understand....I am still learning....and probably will be for the rest of my life...once again thank you very much..your comments have given me another perspective on this....
Cheers,
Bernie
P.S. The next chore is to figure out how to get rich without doing any work...I was told politics is the way to go...

[Chuck H]

The next chore is to figure out how to get rich without doing any work...I was told politics is the way to go...

Well... It's not quite "no work", but it's "low work". "Hit man" is the way to go! I haven't tried it myself... But I'm getting closer every day.

[Enzo]

Chuck, I think you just explained "Ours go to eleven."

[Chuck H]

Actually, I just make ten one louder and have that be the highest number.