Potmeter confusion

[cab42]

Hi List

I need some terminology clarification.

Yesterday I went parts shopping and ended up rather confused (and poor ).

I know that logarithmic pots sometime are called A for Audio in schematics.

Then the guy in the shop told me that linear pots are marked A (eg. 100KA), log pots are marked B and inverse log pots are marked C.

I have seen in some schematics (eg. ROG Ruby) that the pots are designated B. Is that log pots as in the marking on the pot, or is it lin pots as opposed to A(udio) in schematics???

I haven't been able to find anything on 'B' pots in my electronics basic textbook or in the faq.

Thank's in advance

Carsten

[Ge_Whiz]

Confusing, isn't it?

Usually, logarithmic pots are labelled type "A" and linears, type "B". However, there are a number of manufacturers who now adopt the opposite convention! You have to be guided by your supplier and the manufacturer's data.

The easiest are those that are clearly labelled "log" and "lin".

[sir_modulus]

Ah the wonders of Electronics.

Usually, this is how it is:

A-Audio Log Potentiometer (usually for volume controls etc..)
B-Linear Potentiometer (usually for standard linear controls)
C-Reverve Audio Log Potentiometer (usually for specialized/rate controls)

And there were some more, but those are impossible to find these days. Even Audio Log pots are getting a bit harder to find these days....Small Bear is one of the few suppliers thesedays who even stock reverse log pots.

Now what's happening, is that some companies are finding that more companies want Linear pots. What they do, is that some are now starting to label the normal pots as 100KA (and that would be 100K linear), as that would be a standard value asked. Now the speciality Audio pots would get the 'B' marking. That would mean that 100KB would now be 100K audio.

You don't need to worry about this too much, because at the moment, my four main potentiometer sources (Alpha, CTS, MODE elec., Piher) are labeling their pots the old way.

Cheers,

Nish

[toneman]

it should say on the packaging if U R getting at RatShack.
Otherwise, places such as Mouser, list it as Audio or Linear.
Lastly, use an *analog* meter 2 check the taper.
staytuned
tone

[cab42]

Ah, the great thing about standards is that there are so many of them!

Thanks' for your answers.

use an *analog* meter 2 check the taper.

Why an analog meter?? I seem to have success by using my DMM first measuring the resistance in the extreme positions of the pot and then half way between the two. If the resistance is app. half the max its a linear.

My problem is not so much finding out what I have, more like what I have to buy when reading the schematics. I'm still in doubt with the Ruby Amp :oops:

Regards

Carsten

[Ge_Whiz]

It's worth remembering a tip from this forum some time ago; substituting a log for a lin pot (or vice versa) of the same value will not stop any circuit from working, only make the apparent adjustment different.

When I started out on this guitar thing (early 1970s), guitar volume controls were always log ("your ear works this way") and tone controls were linear. Now, most guitar parts suppliers will tell you the opposite. Go figure.

[Satch12879]

Ah, the great thing about standards is that there are so many of them!

You're mad!!! The point of standards is that everyone adopts a single set of rules so to make operations more efficient, speedy, and secure.

And Honeywell/Clarostat makes linear, log, and reverse log pots, so the notion of unavailability is unfounded.

[SnooP_Wiggles]

i have a pot which is a labelled as W100k. its for a wah pedal any ideas as to whether that means its a standard log taper or semi log like an icar?

[cab42]

Ah, the great thing about standards is that there are so many of them!

You're mad!!! The point of standards is that everyone adopts a single set of rules so to make operations more efficient, speedy, and secure.

Yeah.. first time i've ever been called mad in a public forum  

maybe I should have put a smiley in the end of the statement.

But of course you are right. Unfortunately its a problem to agree on which set of standards to be used. National pride, economical interests etc. is an effectice obstacle for developing effective standards in many fields.

Regards

Carsten

[NaBo]

i have a pot which is a labelled as W100k. its for a wah pedal any ideas as to whether that means its a standard log taper or semi log like an icar?

well, if you HAVE it, as in physically have it... then just crack out your meter and test it