Taper of Potentiometers

This is something I never even thought about, but it makes a lot of sense. I recall buying replacment pots for old tube gear, some 45 or more years ago, and you bought them without a switch, and bought the switch separately, which then attached to the rear of the pot. Apparently those pots were made to be used with a switch, but also worked without one. I never noticed any "dead spots" on them, or had problems where I could not turn the volume down low enough. Apparently that was all taken into consideration when they were made. But back then, it was a lot simpler. You chose audio and linear taper, and the correct resistance, and shaft length. That was about it. I recall getting many with LONG shafts that had to be sawed off and a flat spot filed onto the shaft.

The good thing back then is that the shafts were all metal and did not break off.

Reply to
oldschool
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Have you ever dipped the tip of a cigarette in gasoline and tried it?

Reply to
bruce2bowser

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** Like other senses, hearing responds to *percentage" changes in sound level.

The ideal volume control produces similar percentage changes for similar rotations or small movements. Good "log" pots have three linear sections that approximate the ideal fairly well.

.... Phil

Reply to
Phil Allison

Don't try to pull that cotton/polyesther wool substitute over my eyes. Your nominal line voltage is 240. So that means it is like me having one that goes to 130. Yours would have to go to 150 to be equivalent.

What impresses me (some) is how some of these modern power supplies can handle auto-swicthing between line voltages.

Reply to
jurb6006

As soon as my son teaches me how to scan on my new printer, I will post an old catalog page with many tapers shown. I will try to put in the drop box. I think the page was from an old Centralab catalog. CP

Reply to
MOP CAP

drop box."

Too bad. Dropbox doesn't want to display for me. It might be because I used to be a member ad gave it up. I am currently looking for free hosting that is compatible with my browser.

I don't mind an ad or two but I don't want people to have to sign up or sign in and that is what it is doing for me.

Reply to
jurb6006

All that is what makes things 'interisting'. I believe the K is for Kelvin temperature and that made them use the k for 1000.

Too bad that many companies seem ot use their own code for part numbers. I really hate the companies that use their part number on standard parts and if you need to replace them, you are almost forced to go to the origional company or one of their repair man. Friend in the auto repair business told me that often a luxulary car part would be the same as a less expensive model. They use a different number and higher price.

Reply to
Ralph Mowery

If you give it a thought, you will realize a linear pot is its own reverse. The reverse doesn't refer to whether the resistance goes up or down, it refers to which direction the log curve goes, a log taper or an exponential taper. A linear taper is the same either way... it's linear.

--
Rick C 

Viewed the eclipse at Wintercrest Farms, 
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Reply to
rickman

Log taper means mimicing log(d) where the deflection (d) goes from

1 to 100 or somesuch. Inverse log taper means mimicing log(1/d) = - log(d)

So, linear taper can mimic 'd', and its inverse can be '-d', as you say. Or, linear taper can be 'd', and its inverse can be '1/d'.

The '1/d' taper would be a way to make an adjustable attenuator, linear in inverse gain going from '1' meaning full signal, to '2' meaning 1/2, ... '10' meaning 1/10

Reply to
whit3rd

Then it is no longer linear.

--
Rick C 

Viewed the eclipse at Wintercrest Farms, 
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Reply to
rickman

Congratulations, not only are you ignorant, you have no sense of humor.

--
"I am a river to my people." 
Jeff-1.0 
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Reply to
Fox's Mercantile

I would very much expect he didn't need to 'give it a thought' to work out something so obvious.

NT

Reply to
tabbypurr

Dropbox does not support Samsung devices for what that is worth. Or so they tell me.

Peter Wieck Melrose Park, PA

Reply to
pfjw

And yet, he mentions he has never seen a reverse linear taper.

--
Rick C 

Viewed the eclipse at Wintercrest Farms, 
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Reply to
rickman

Back when I was a journeyman electrician, and therefore was privileged to h aze the apprentices, I asked one to fetch me (amongst many other things) a combo-plate from the warehouse like this:

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And when he brought me this:

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I sent him back, stating I needed the receptacle on the left.

He got as far as the door before he caught on. And it never happened to him again. Others got all the way to the counter at the warehouse.

Peter Wieck Melrose Park, PA

Reply to
pfjw

I have repaired many broken plastic parts. I have a kit with 0.025" and 0.035" drill bits and matching steel rods. I put the parts together, then drill through where inserting a steel pin will give it the most strength. I epoxy the joint and the pin and put it all together. I use a Dremel tool to drill the hole and and cut the steel pin off, after the epoxy sets. The epoxy I have is Huntsman Fastweld 10, (ex. Ciba-Geigy Araldite) It is a 5 minute set 24 hour cure.

Mikek

Reply to
amdx

In my late teens a father bought his daughter a Volkswagen Beetle, the first thing he did was send her to go to the gas station* and have them check the water in the radiator.

Mikek

  • back when they had service at gas stations.
Reply to
amdx

Hah! Square-root taper :) Probably good enough for rock-n-^H^H^H^H^Haudio

If you know the source and load impedance of the pot, wiring a linear pot with the input to the wiper and output from the top gets you somewhere close to the same effect.

Reply to
Clifford Heath

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** FYI:

A simple way to get *very repeatable* "log" type curve for audio is to wire the two sections of a dual linear pot in series. The wiper of the first half goes to the top of the second and its wiper becomes the output. Bottom ends are both grounded.

At the centre (50%) position, this reliably gives -15dB attenuation when loading effects are taken into account.

At the 75% setting, attenuation is -6.5dB, at 25% it is -25dB while down at 10%, attenuation is -40dB.

..... Phil

Reply to
Phil Allison

They got me once at the TV parts store. I needed a 223" color CRT for a Motorola. The guy says he only had 25" CRTs right now. I said "How am I going to fit that ?" and he replied "A cabinet stretcher". I said "OK, where do I get one of those ?".

Once and only once...

Reply to
jurb6006

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