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  #1  
Old 04-24-2009, 03:58 AM
frenchie29 frenchie29 is offline
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Default difference between potentiometer A and B

I totally forgot about that one

What's the difference between potentiometer type A and B?

And the one that's the most used for audio?
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Old 04-24-2009, 06:37 AM
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Hello,

Do you mean the diffrence between linear and logaritmic potentiometers?
Here is a link called "The Secret Life of Pots", with a lot of information on potentiometers.
http://www.geofex.com/Article_Folder...s/potscret.htm

The link comes from the EDUCYPEDIA on Resistor technology.
http://www.educypedia.be/electronics/resistors.htm

Greetings,
Bertus
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Old 04-25-2009, 12:11 AM
frenchie29 frenchie29 is offline
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There's no mentioning of A or B type!! Unless I didn't see it. I remember well A=audio taper log. But I am not sure anymore.
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Old 04-25-2009, 12:25 AM
frenchie29 frenchie29 is offline
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I need to replace that trim pot for this project

http://www.kitsrus.com/pdf/k17.pdf
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Old 04-25-2009, 12:28 AM
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That's a log pot. You could use an audio taper pot.
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Old 04-25-2009, 01:00 AM
frenchie29 frenchie29 is offline
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So type A??? The thing is that trimpot that came with that kit says 10KB on it. That's why I'm a bit confused. Also I want to use a TRS female connector for the audio input.

Tip to audio in
Ring to audio in
Sleeve to ground audio

Is that right?

Quote:
Originally Posted by SgtWookie View Post
That's a log pot. You could use an audio taper pot.
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Old 04-25-2009, 02:06 AM
Darren Holdstock Darren Holdstock is offline
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I don't recall ever seeing a log trim pot - they seem to have specified a log pot in the schematic, but supplied a linear pot with the kit. It won't matter if you're just using the pot to set the gain just the once, it's only if it's being used as a working volume control that it might become annoying as the relationship between pot rotation and perceived loudness is non-linear with a linear pot.

An old trick to make a lin pot a bit more loggy is to add a resistor from wiper to ground - it quite often makes a more repeatable pot, as log pots are very hard to make accurately, and the tracking between dual log pots can be poor. Bertus' link (above) explains more about this technique.
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Old 04-25-2009, 02:30 AM
frenchie29 frenchie29 is offline
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I have both 10k A&B 25kB and 50k audio log (A) Now I know that the A type is for audio it says it on the 50k pot Which one would work best? I don't really want to use the 50k they cost me like $5 each
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Old 04-25-2009, 03:01 PM
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You need to use a 10k Ohm pot, otherwise you will have an impedance mismatch. Line-level audio is designed for 10k Ohm impedance. Using an incorrect resistance pot may result in distortion.

If you use an audio taper pot but install it backwards, it will seem like you have almost no control over the volume for most of the pot's travel; the volume will suddenly go from almost nothing to almost full blast. If that's the case, you'll need to swap the two outside leads on the pot.

The center lead is the wiper; it must be connected to the input of the amplifier IC.
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Old 04-25-2009, 03:54 PM
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I think I have the wiring right I used a 10k pot. The thing is, when the pot is barely open I get major distortion then when I turn it clockwise it gets cleaner and the volume increases. Is the distortion cause by not enough audio signal? That's weird I've never heard that before.
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