HELP: Linear VS audio taper

[asmiroth]

hello everyone im just new hear and im asking a noob question...

here it goes...

at our place the audio taper pots arent available only the linear ones...
what if the schematic requires a audio log pot but i substitute a linear pot
will there be a big difference? what would that be..
sorry for the noob question thanks

[madbean]

Well, it's an easy question but fundamental to understanding how to build effects, so it's good that you asked!

You can always substitute linear for audio and vice-versa. This will never cause your effect to become inoperable. What it can change, though, is how a control responds. There are two reasons we use audio tapers. One is that an audio taper attempts to mimic how the human ear responds to small changes in volume. We hear perceived changes in volume on a logarithmic (ie exponential) scale rather than a linear one. So, rather than creating a 1:1 correspondence between resistance on the pot wafer and rotation of the pot shaft, the audio taper breaks it down into two parts. The first part uses more resistance in the first half of the rotation and the second part uses less. This means as you turn the pot up halfway, you have traveled a little more than half the value of the pot's total resistance. Turning it up further means you use up the remaining resistance in less space: this is close (although not exact) to a logarithmic scale.

The second reason we use audio taper pots is that with some controls, it is better have more control over one half of a pot than another. For instance, in a Fuzz Face, the standard pot for the fuzz control is a 1kB. However, a common complaint with this effect is that all the Fuzz bunches up at the very end of the control. In this case, using a reverse-audio taper (the opposite relationship of what I described above) evens it out. Less resistance is used in the first half of the control, and more resistance is used in the second. This gives you greater control over small changes in Fuzz, which makes it a much more useful control overall.

So, using a linear as a sub for audio can change how the control responds. It could be unoticable, or it could be bothersome, depending on the set up you are using. Note that you can turn a linear pot into somewhat of an audio pot by using an additional resistor. By placing a resistor across lugs 3 and 2 of a linear pot, you are in effect reducing the overall resistance on one half of the taper (remember that putting resistors in parallel reduces their overall value). So, if you took a 100kB pot, and put a 47k resistor across lugs 3&2, you have essentially shifted a larger portion of the resistance to the first half of the taper---i.e. an audio pot.

[CK1]

Great explanation, Brian!  Thanks for that.

[asmiroth]

Well, it's an easy question but fundamental to understanding how to build effects, so it's good that you asked!

You can always substitute linear for audio and vice-versa. This will never cause your effect to become inoperable. What it can change, though, is how a control responds. There are two reasons we use audio tapers. One is that an audio taper attempts to mimic how the human ear responds to small changes in volume. We hear perceived changes in volume on a logarithmic (ie exponential) scale rather than a linear one. So, rather than creating a 1:1 correspondence between resistance on the pot wafer and rotation of the pot shaft, the audio taper breaks it down into two parts. The first part uses more resistance in the first half of the rotation and the second part uses less. This means as you turn the pot up halfway, you have traveled a little more than half the value of the pot's total resistance. Turning it up further means you use up the remaining resistance in less space: this is close (although not exact) to a logarithmic scale.

The second reason we use audio taper pots is that with some controls, it is better have more control over one half of a pot than another. For instance, in a Fuzz Face, the standard pot for the fuzz control is a 1kB. However, a common complaint with this effect is that all the Fuzz bunches up at the very end of the control. In this case, using a reverse-audio taper (the opposite relationship of what I described above) evens it out. Less resistance is used in the first half of the control, and more resistance is used in the second. This gives you greater control over small changes in Fuzz, which makes it a much more useful control overall.

So, using a linear as a sub for audio can change how the control responds. It could be unoticable, or it could be bothersome, depending on the set up you are using. Note that you can turn a linear pot into somewhat of an audio pot by using an additional resistor. By placing a resistor across lugs 3 and 2 of a linear pot, you are in effect reducing the overall resistance on one half of the taper (remember that putting resistors in parallel reduces their overall value). So, if you took a 100kB pot, and put a 47k resistor across lugs 3&2, you have essentially shifted a larger portion of the resistance to the first half of the taper---i.e. an audio pot.

thank you very much brian i just put a 22k between lugs 2 and 3 and it worked well thanks!
another question though....
how do we convert a linear pot into a reverse audio? hehe
i built a slambox but i used a 5k linear pot, i wanted it to be almost a work alike of a reverse audio like what in the layout says..
thanks again!

[madbean]

Try using a 10kB pot with a 5k1 across lugs 2&1.

[CRBMoA]

THIS is a great read.

[jkokura]

Chris, your links tend to pop up with FTP:// in front. Is there something you're doing when you link your words that would make this happen? Is anyone else having this happen or is it just me and my macintosh ways?

jacob

[gtr2]

Chris, your links tend to pop up with FTP:// in front. Is there something you're doing when you link your words that would make this happen? Is anyone else having this happen or is it just me and my macintosh ways?

jacob

I don't see it.  I'm on a windows pc still.  But I love my iphone.  (sorry for the offtopic)

[pauloman80]

Chris, your links tend to pop up with FTP:// in front. Is there something you're doing when you link your words that would make this happen? Is anyone else having this happen or is it just me and my macintosh ways?

jacob

I see it as well, and I'm also on a Mac.  Not sure why it happened, but that's why my keyboard has a backspace key.    Still odd that it did that, though...

[CRBMoA]

Chris, your links tend to pop up with FTP:// in front. Is there something you're doing when you link your words that would make this happen? Is anyone else having this happen or is it just me and my macintosh ways?

jacob

Not really sure. I am a posting whore, and I often grab things from one place and link/embed/post them somewhere else. It might be the source I am using. I think some of the FSB stuff might not like being yanked. I actually clicked on my own link and got the same thing. WTH?