Regarding Pots: B10K vs A10K?

[darko28064212]

hello all,

this is in regards to my love squeeze clone build, but i also feel its vague enough to shed light on why we would choose B10K pots over A10K pots and vice versa. I was under the assumption that i was supposed to use B10K (linear) pots. but recently i was pointed towards the "Rotten Comp" PCB which is modeled after the love squeeze.

PCB and BOM for the Rotten Comp by GCFX:
https://dl.dropboxusercontent.com/u/28586266/GCFX%20Build%20Docs/RottenKompBuildDoc.pdf

this is the first time ive seen real directions for A10K (audio) pots being used for the build. why audio pots? wouldnt you want your controls from 0-10 on the knob? im questioning my understanding of the difference between these 2 choices. please help?

[benlanc]

You generally use Audio pots (aka Logarithmic taper) because your ear responds to sound in a logarithmic way, they're generally found on attenuating volume controls (those that reduce the volume by bleeding an amount to ground) but they have other uses too.

With a linear pot, all of the change would happen at one end of the wiper, logarithmic "feels" a lot more natural as you go from 0 - 100%.

Here's a handy illustration (bare in mind that bels is a logarathmic scale too):

[alanp]

http://www.geofex.com/article_folders/potsecrets/potscret.htm

Scroll down to Pot Tapers.

Short answer, sometimes all the interesting changes that the pot makes are bunched up tightly at one end or another of the pot's rotational travel. Changing which taper pot you use spreads the interesting part across more rotational travel, if that makes sense.

[midwayfair]

Here's a handy illustration (bare in mind that bels is a logarathmic scale too):

That graphic is incredibly inaccurate. Almost like someone was just making stuff up.

Take a 1K log pot and a 1V signal. The pot forms a voltage divider.

50% of the pot's travel is 10% of the resistance. Your output voltage is .1, or -20dB. NOT -50dB! -50dB would require that your pot's set at only 3R:997R, which is probably less than 1% of the pot's travel and also an unrealistically difficult setting to ever get in real life. The -90dB shown at 10% of a log pot's taper would require LESS THAN AN OHM between the wiper and one of the outside lugs. There is no pot with a taper like that. If you want to test it with the actual travel of a real-life pot, you can nab a log pot with detents and measure the resistance. You'll find that 10% of a log pot's travel is actually more like -32dB or so. Even log pots cannot realistically be expected to reduce the signal much more than that.