I found this article that has a good explanaiton of potentiometers, linear, audio etc.
http://www.geofex.com/Article_Folders/potsecrets/potscret.htm
Gary
:Can someone explain what the difference is between linear and audio potentiometers and how to determine what you need when replacing one?
::Can someone explain what the difference is between linear and audio potentiometers and how to determine what you need when replacing one?
Gary, Great article, Many thanks!
Jon.
Ohhh tay, well it seems that the human ear……along with several other mediums in the laws of physics respond in the law of inverse squares. Specifically, regarding our hearing, is the fact that our hearing sensitivity is greatest in perceiving the lower power levels of sound. A person with normal hearing perceives and picks up on very weak sounds quite well. However as the sound levels increase the ear starts responding in a non-linear logarithmic mode.
For example, if we listen to a sound bite and perceive its intensity and then up its volume level where it seems to be twice as loud as it initially was , we would find that level actually had to be increased to four times the initial level in order to seem twice as loud.. The same , technique on up the power scale where we would then have to increase the initial level 16 times to perceive of a doubling that previous level.
The same holds true in the adjustment of a volume control on the front of an audio amp and its output on to a power amp and driving a speaker to produce your sound. If we were to use a linear pot in that function we would find that its control would be quite compressed and within a small portion of the rotation of that control in its lower….towards ground…positioning of its wiper element. HOWEVER if a logarithmic taper pot was used with its spread out change of resistance spread out on that lower volume portion of its rotation, we would then find the acquisition of a much more controllable volume adjustment as compared to the like use of a linear pot in its position , wherein the complete volume control span would occur in a very small portion of the pots range with only a minute movement of the conrol.
In the past I have seen upwards of 4 different tapers the most common being the linear, then the logarithmic, also a reverse logarithmic and the 4th was so infrequent that it was a quasi semi logarithmic, very seldom used.
Now you ask, how do I know when I have a log (audio)pot, well its as simple as taking an ohmmeter in hand and measuring across its end terminals. Say we found that pot was found to be a 500k pot then if we were to eye the control shaft and figure it to encompass 270 degrees with in its rotation, then we could guesstimate that pots center position and position it there and then take a reading of resistance from the center rotor to the outer lead that normally goes to ground. Should that pot be a linear one we could expect a 250 k reading. Next divide that positioning in half in its rotational positioning and then expect half of that…or a 125k reading and that will further halve into ~62k for an 1/8 positioning of the control. So that is the manner of testing to differentiate as to your having a linear curved pot taper.
Lastly, should you have found a pot at center range that was reading ~62K and then adjusted it to ¼ positioning and read ~15K and then finally to 1/8 position with an ~4k reading, you would have a log audio taper control in your hands.
You can readily see how those gradual….spread out with rotation…. resistive changes would more appropriately suffice in a spread out transitioning of the sound at lower volume levels, where our hearing is most perceptive.
Then there’s the Fletcher-Munsen curve of hearing response in relevance to tonal response of the human hearing……..but that’s a whole ‘nother story.
73’s de Edd
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:Can someone explain what the difference is between linear and audio potentiometers and how to determine what you need when replacing one?