pot values

Discussion in 'Amp Tech Center' started by 8urchevy, Apr 14, 2019.

  1. 8urchevy

    8urchevy Tele-Meister

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    Hello everyone. I was wondering about pot values as far as how they are chosen in the design process and how changing the value affects the circuit. For example, master volume, gain, and tone pots. Typically for example we see 1M audio volume pots used.

    I have several 500k pots that I removed from that PA head I converted to guitar amp and would like to use them in something in the future. Perhaps they would be suitable for volume and tone pots?

    Thanks
     
  2. Finck

    Finck Tele-Afflicted

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    The values of the pots affect strongly the behavior of a tone stack. There are some PC programs/calculators that can help you to check that behavior with different values.

    In a simple tone control (cap plus pot to ground), it will affect the actuation range of the circuit, since it forms a filter with the tone cap. I see no issues in using a pot larger than original, but a lower one can cut higher frequencies too much.

    When used as gain or volume controls on an amp or pedal, the impact depends on the circuit, but I'm not able to give you a good explanation. I just know that a circuit usually doesn't stop working when you use a higher value pot.

    I'm almost sure the above explanations are poor...
     
  3. 8urchevy

    8urchevy Tele-Meister

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    Sounds good to me. Thanks .I have seen a few schematics using 500k as volume pots. Just not sure what circuit attributes decide the volume pot choice.
     
  4. Finck

    Finck Tele-Afflicted

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    If used at the end of a certain circuit (or at the end of a partial block) the pot will define its output impedance, I guess.
     
  5. peteb

    peteb Friend of Leo's

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    In a Tele, bigger pots than the normal 250k were used, possibly both the tone and the volume. I believe bigger pots in either position make the tone brighter. 1M was used starting in 69 (Duchossoir). He says the the 250K has smoother taper but less highs than a 1M pot.


    Going from 1M to 500k in an amp might not be the right direction to go.



    It seems like higher values for tone or volume in the amp or the guitar is going to prevent signal loss or at least signal loss in the higher ranges.
     
  6. DonM

    DonM Tele-Afflicted Silver Supporter

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    Pot values; I pay twice as much in Las Vegas as I do in SoCal. Then I read the post. :cool:
     
  7. clintj

    clintj Friend of Leo's

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    Smaller value pots will load down the preceding stage more and overall will attenuate the signal. If you need to trim a little gain, it's a good use for them.

    A consequence of large value pots I could see is possible blocking distortion in the stage they feed. The pot usually forms the grid leak path of the following triode, so unless measures like separate grid stoppers are used grid current could raise its head at high settings with high amplitude signal.

    Sent from my Pixel 2 using Tapatalk
     
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