inverse log potetiometers ?

Is there any inverse log/audio potentiometers in the market (mouser or digikey ?) ? I need potentiometers which resistor values decaying fast from bigger to small values when they turn clockwise.I can use regular audio potentiometers but unfortunately to get this effect I have to turn them CCW.Thanks for your help.

Oye

They are very difficult to obtain. Pro-audio equipment is the only sector I know that regularly uses them.

If you want a value other than 10k or 100k I'd look for another solution ! Your best bet is likely to be an Alps part btw. Mouser or Digikey may well have them bit I'll leave it to you to look. What you want is a 'C' taper. Or even Alps's 'RD' taper if they have it.

Graham

know

But you can get the effect of a log potentiometer with the proper value resistor from the arm to one of the fixed ends of the pot. It's been written up lots of times, and I recall something in "Electronics" about using an op-amp for an improved implementation of it.

If it gives satisfactory results, then the inverse effect can be done with putting the resistor to the other end of the pot.

Michael

know

Yes I know, but in audio, both applications that regularly require 'antilog' pots aren't actually voltage dividers, so it doesn't help.

Graham

Isn't inverse log the same as exponential?

Bill

In what was is that supposed to help ?

Funnily enough it's the classic 'log pot' that actually has an exponential style law.

Graham

You found a supplier OK then ? Do you have a link, it might be useful for future reference.

Graham

Thank you !. yes, Alp have taper C.I never know that taper C is inverse log pot.

Oyek

Eeyore wrote:

know

pots

Here is the link I am looking for :

or you might go to their main website:

Oye

Eeyore wrote:

future

I first thought that there was something badly wrong but on checking I find that taper designation has been changed. As I was aware the C taper is the normal log taper, but it seems that a log taper is now an A taper. Originally in my radio repair era, the A taper was the linear pot. So all I can say, is to be wary of the taper designation, and check that it is the style you really intend. See also

Peter Dettmann

future

But did you find a stockist ? That's my point.

I know very well Alps have this item in their catalogue (that's why I suggested them), but it is not widely stocked. Usually it is only made to special order.

Yes I know who Alps are thank you. You may recall I suggested them. Taiwan Alpha is the other company who may be useful.

Graham

The C taper was *never* the normal audio log (volume control) taper in my (very long) experience.

There has been a difference between the designations used for linear and log between European and Japanese (and other Asian) suppliers though.

A = 'log' - audio volume control taper (JIS) Japan Industry Standard BUT LINEAR EUROPEAN STANDARD.

B = linear (JIS) but audio taper for European suppliers.

C = 'reverse log' always.

Graham

Peter Dettmann wrote in news: snipped-for-privacy@4ax.com:

Thankyou. Extremely useful article to link to. The rest looks set to occupy a lot of my time too.

That is interesting Graham, as I had (from the 1950's) always found the C designation to be the audio taper used in radio and amplifiers. You have noted some of the less important areas like European, and Asian, but in the center of the universe (Australia) we seem to have our own 'standard'. From the 1992 Dick Smith catalogue, the following are stated: A = Linear B = Logarithmic C = Logarithmic E = Anti-Log J = Linear

On looking through my junk box, all the C's all measure as log, and all the A's are linear. Another designation I found was W which is a Wire Wound pot.

I can understand now that pots marked 'Log' or 'Lin' are a much safer method.

Peter Dettmann

(very

Dick Smith is wrong.

You're unlikely to find pots marked log or lin any more in my considerable experience..

Graham

In your realm he may not be right, but he is certainly not wrong.

You have to read the whole thing, and forget your limited experience. The whole point is that there has been no universal standard, so I am in difficulty understanding why you are disputing this basic fact when it has been authenticated.

Quite true Graham, but your considerable expeience is not considerable enough. Even in my limited experience, we do get pots marked Log, or Lin. That is fact.

Peter Dettmann

My alleged 'limited experience' includes designing mixing consoles for Neve, DDA and Studiomaster. I ma quite intimately familiar with pot specs in fact.

Whereas you have nothing more than 15 year old Australian hobbyist catalogue to offer.

I suggest you start by examining the taper drawings on page 4 of this document.

Yes, some companies use other designations (American makers especially) but you'll find the Alps laws widely copied. and they're as close to a 'standard' as I know. Several of them are JIS ( Japan Industry Standard).

Graham

Sigh ..... Graham, you again miss the point. You seem to state unequivocally that a C taper is nor ever has been used anywhere regularly as a Log taper. You based this on your wide experience. Well my friend, your wide experience is obviously not wide enough.

Your experience on some mixing consoles is commendable, but hardly adequte. My limited though wider experience on radio repair and electronics, over several decades of design and manufacture show that your bald statement is only true in a limited area. I did not consider that an astute person would need more than one reference to show that the C Log taper is and has been used. Live with it. As I said earlier, this has been in use since at least the early

What is or is not standard now is not the question, if you read carefully the matter dealt with what was used, and that is not in doubt. C taper was certainly used extensively, and for many years as a Log designator. You have not shown otherwise. End of story.

Peter Dettmann