Potentiometer sensitivity

Discussion in 'General Electronics Chat' started by RyanBRZ, Oct 30, 2014.

  1. RyanBRZ

    Thread Starter New Member

    Oct 22, 2014
    12
    0
    I recently replaced a potentiometer on an amplifier, using the same level resistance as the original (20k linear). I noticed that once I get to about 30% (turned clockwise) I see no difference up to the 100% position. Can I put in a higher impedance pot to get more accuracy so I'll see a level of difference at each position? The original pot that came with the amplifier works the same way.

    Thanks!
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,797
    1,103
    Can you post a link to the schematic of your amp?
     
  3. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
    2,804
    832
    Are you sure it was a linear pot?
     
  4. alfacliff

    Well-Known Member

    Dec 13, 2013
    2,449
    428
    volume controll pots are not usually linear, they use log taper pots to mimic the response of the human ear. that keeps the volume changes from crowding up at the bottom of rotation.
     
  5. RyanBRZ

    Thread Starter New Member

    Oct 22, 2014
    12
    0
    The pot that came with the amp is stamped B203; I used a DMM, set it to 20k and it reads 19.5 at full resistance and the taper is definitely linear. This is for gain control on the amp, I'm not sure if that's considered the same as volume but I suppose it's the same right?

    I'm better off with log taper?
     
  6. crutschow

    Expert

    Mar 14, 2008
    13,006
    3,232
    Yes, a log taper should give you a more linear pot movement relative to the perceived sound level.

    You can mimic the response of a log pot reasonably closely by putting a 2k to 3k ohm resistor from the wiper to ground. You might try that to see how it works. The only problem would be if the source can't linearly drive the lower resistance that this configuration provides. If so, you would need to use a 200k ohm pot and a 20k to 30k ohm resistor.
     
  7. RyanBRZ

    Thread Starter New Member

    Oct 22, 2014
    12
    0
    Is a log pot preferable over the alternative? I just ordered the 20k log pot.
     
  8. MrChips

    Moderator

    Oct 2, 2009
    12,440
    3,361
    What is the resistance when the knob is turned halfway?
     
  9. RyanBRZ

    Thread Starter New Member

    Oct 22, 2014
    12
    0
    ~10
     
  10. MrChips

    Moderator

    Oct 2, 2009
    12,440
    3,361
    If it is 10kΩ at midpoint then it is linear.
    A 20kΩ log pot should be better.
     
  11. RyanBRZ

    Thread Starter New Member

    Oct 22, 2014
    12
    0
    Switched to log pot and it works perfect. Thanks for the help!
     
Loading...