Log/lin pot A/B suffixes & prefixes

[N Cook]

Does anyone know of any standard or authorative source for such
designations.
eg
50KA - lin ?
50KB- log ?
50KAB - lin/log , semilog?
50KBA - log/lin ?
and does a B prefix mean a centre pick off fourth terminal, or 1/3&2/3, or
any fixed track tap terminal or what if anything a B prefix means. ?
And while at it any other letter designations eg for cosine track, or even
wire/wound etc

 

[Ron(UK)]

Does anyone know of any standard or authorative source for such
designations.
eg
50KA - lin ?
50KB- log ?
50KAB - lin/log , semilog?
50KBA - log/lin ?
and does a B prefix mean a centre pick off fourth terminal, or 1/3&2/3, or
any fixed track tap terminal or what if anything a B prefix means. ?
And while at it any other letter designations eg for cosine track, or even
wire/wound etc

I think it`s A = lin, B = log except when it isn`t

the marking conventions changed some time ago

Pot Markings
Now, this should be dead easy - a simple code to indicate the resistance and law of a pot should cause no grief to anyone, right? Wrong! It wouldn't have been so bad if someone hadn't decided to change it, and even then, it wouldn't have been so bad if there was no overlap between the "old" and "new" "standards" ... I think you can see where this is headed by now.

Taper Old Code New Code Alternate
Linear A B LIN
Log (Audio) C A LOG
Antilog F N/A N/A

Wasn't that a nice thing to do? It is obviously important to check before you make assumptions, or you can easily get the wrong type - especially if working on older equipment.

At least the resistance marking is usually sensible, so a 100k pot will be marked as 100K - but not always. The coding system used for capacitors is sometimes used as well (especially on small trimpots), so a 100k pot could also be marked as 104 - 10, followed by 4 zeros, or 100000 (100k) ohms.

http://sound.westhost.com/pots.htm#markings

Ron(UK)

 

[Dave Plowman (News)]

http://sound.westhost.com/pots.htm#markings

Ron(UK)

Are you the author? If so, congratulations for a useful little piece.

 

[Ron(UK)]

Are you the author? If so, congratulations for a useful little piece.

No no, it`s part of a wonderful resources site ESP which contains a
huge amount of useful info http://sound.westhost.com/

I thought that I`d put a attribution to the site just before my header,
but it seems to have gone awol.


Ron(UK)

 

[Eeyore]

Does anyone know of any standard or authorative source for such
designations.

A = linear (European) or Audio taper (Japanese).

B = 'log' taper (European) or linear (Japanese)

Graham

 

[Eeyore]

I think it`s A = lin, B = log except when it isn`t

the marking conventions changed some time ago

There are no meaningful conventions except that C universally means 'reverse log'.

Graham

 

[N Cook]

A = linear (European) or Audio taper (Japanese).

B = 'log' taper (European) or linear (Japanese)

Graham

so its a matter of ignoring everything other than the likes of 50K and
measuring ohms at 1/4,1/2,3/4 and full track

 

[Ron(UK)]

so its a matter of ignoring everything other than the likes of 50K and
measuring ohms at 1/4,1/2,3/4 and full track

connecting the pot to an analogue meter and sweeping from end to end
will show whether it`s log or lin.

Ron(UK)

 

[Eeyore]

Eeyore wrote


so its a matter of ignoring everything other than the likes of 50K

What does the resistance value have to do with it ?

and measuring ohms at 1/4,1/2,3/4 and full track

1/2 rotation only. Most of the tapers you're likely to find in audio are
typically specified @ 50% rotation as a percentage of 100% resistance. Audio and
reverse log are usually 15% for example (depending which end you're measuring
from) although I have used semi-specials such as 5% reverse log for mic amp gain
pots.

Graham

 

[Dave Plowman (News)]

connecting the pot to an analogue meter and sweeping from end to end
will show whether it`s log or lin.

You don't even need to go that far. Set to approx 1/2 travel and measure
one side. Linear will be near 50% - log very much not.