Audio / Linear Taper

[selloutrr]

Has anyone experimented with 1 Meg Linear Taper Potentiometers in place of the suggested Audio Taper pots on the Express?

The reason I ask I bought a batch of TW correct wire wrap pots but they are Linear not Audio taper. If it's a bust I can still harvest the back plates.

[Firestorm]

I suppose you could experiment with 1ML for the treble pot; bass pot, eh, maybe; volume pot probably not.

[selloutrr]

I'm just glad to have the correct back plates. I have twist wrap wipers I can swap out.

I figured since most of the time the amp settings are set and forget in the big scheme of things it wouldnt be a huge issue.

[diagrammatiks]

for anything other then volume linear taper is alright. it'll just have different response depending on where the pot is set.


A linear taper should be 50 percent right at the midway point of rotation.

an audio pot could be 50 percent at about 1/3 or 1/4 of the rotation with the reminder the rest of the pot.

there is a way to change the taper of a linear pot slightly to resemble an audio pot, however the overall value of the pot will be reduced slightly.

[selloutrr]

You can change the Linear response to Audio by bridging the wiper to ground thru a resistor 25% of the pots value. Effectively making a 500K pot 375K or a 1Meg pot about 750K.

[martin manning]

...You can change the Linear response to Audio by bridging the wiper to ground thru a resistor 25% of the pots value. Effectively making a 500K pot 375K or a 1Meg pot about 750K.

The down-side to this is that the resistance across the element will change with the setting from full-value at 0% rotation down to 20% at 100% rotation. If the pot is functioning as a load on the circuit feeding it, this could be a problem.

[Vince]

You can change the Linear response to Audio by bridging the wiper to ground thru a resistor 25% of the pots value. Effectively making a 500K pot 375K or a 1Meg pot about 750K.

Really?

500k || 125k = 100k
1M || 250k = 200k

I'm missing something or what?

regards
V.

[selloutrr]

Yeah you missing something lol

I'm not following your math
whatever the value of the linear pot is after you add the resistor to fake it react like an audio taper you loose roughly 25% of the original taper.

[Vince]

Yeah you missing something lol

I'm not following your math
whatever the value of the linear pot is after you add the resistor to fake it react like an audio taper you loose roughly 25% of the original taper.

Maybe you: "You can change the Linear response to Audio by bridging the wiper to ground thru a resistor 25% of the pots value"

Yeah?

You want to type: "You can change the Linear response to Audio by bridging the wiper to ground thru a resistor about 3 times of the pots value.
Effectively making a 500K pot 375K or a 1Meg pot about 750K."

Now is better?

[selloutrr]

I see where the issue is. I wasn't understanding your post earlier.

Connect the resistor on to lug 1 and the lug 2 (wiper) of the pot. bridging them via the resistor which is 25% of the total potentiometer value.

I just realized I said ground not lug 1 which threw you. sorry for the confusion.

[Vince]

I see where the issue is. I wasn't understanding your post earlier.

Connect the resistor on to lug 1 and the lug 2 (wiper) of the pot. bridging them via the resistor which is 25% of the total potentiometer value.

I just realized I said ground not lug 1 which threw you. sorry for the confusion.

I understand it correcty first time
But if you connect 125k resistor (25% of 500k) to 500k pot
you will have 100k when pot is fully up
100k - not 375k.
Its about parallel linking resistances.
http://www.sengpielaudio.com/calculator-paralresist.htm

regards
V

[selloutrr]

I've never tried it but that is how it was explained to me.

Im sure it's just making the best or the wrong part for the application so you would have to compromise in some way?

[vibratoking]

It's not quite as simple as has been discussed. You have to look at how the pot is connected - 3 terminal or 2 terminal. 2 terminal doesn't really allow for converting from linear to audio. You also have to look at the source and load impedances to see if there is a loading problem. I am too lazy to look, but as I remember the mid and bass pots in an Express are 2 terminal and all the others are 3 terminal. The loading is another question. Here are some links:

http://www.geofex.com/article_folders/p ... tscret.htm

http://electro-music.com/forum/phpbb-fi ... mz_168.pdf