Potentiometers

Discussion in 'DIY' started by mtoc, Jan 11, 2016.

  1. mtoc

    mtoc SBAF's Resident Shit-Stirrer

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    Just google potentiometers day n night these days while listening to David Bowie and there're many magical things that a good pot can do acorrding to many threads in many bbs(s).

    Does $10 Apls ---> $300 P&G blow some's mind after this upgrading?
     
  2. Smitty

    Smitty Too good for bad vodka - Friend

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    It's more like the better pot gets out of the way of things. Cheap ones can add noise to the signal, or can have static noise when you turn them. The pot tends to be before the amplification stages, so a noisy pot can have a major effect on sonic quality. A good pot is quiet. Also, cheap pots tend to have channel imbalances at the ends of their ranges, but better pots have more careful matching.
     
  3. Josh Schor

    Josh Schor Friend

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    Need some advice from those that know. Is a 100kohm attenuator better sound in a PP tube amp then a 250kohm attenuator?
    best,
    Josh
     
  4. Priidik

    Priidik MOT: Estelon

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    It would make sense to use what was intended in the design. It acts as a load (or part load) to the input stage.
     
    Last edited: Feb 25, 2024
  5. Cspirou

    Cspirou They call me Sparky

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    @Josh Schor - generally you want to avoid higher resistance as it introduces noise in the circuit. If it’s too low and is close to the output impedance of your source than you can get some distortion.

    @Priidik is right though and you should stick to whatever range is mentioned in the build
     
  6. Josh Schor

    Josh Schor Friend

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    Lance Cohcrane built the amp its a kt88 power tube with 12au7 input tubes. He used mono 250kohm pots he says fnot for any theoritical reason other then he likes them. Do you think 100kohm will sound better in this situation?
    best,
    Josh
     
  7. Pancakes

    Pancakes Friend

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    It depends on your upstream component. If it's a solid state component (DAC, preamp, phono stage), you can go as low as 10K. If the upstream component is driven by tubes, you will likely need higher. The value would depend on the output impedance of the source component. Find out what that is. A good rule of thumb is output impedance of source X 100 is minimum input impedance of whatever it's driving.

    For example, I think all Schiit DACs and preamps have output impedance of 75Ohms. Therefore a pot of 7.5KOhms is the minimum of the next component.

    You can go higher but you raise the noise floor the system.
     
  8. Josh Schor

    Josh Schor Friend

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    thank you
     
  9. Josh Schor

    Josh Schor Friend

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    Hi Alex,
    hope your doing well. the builder said its 8ohms output so would a 100kohm be best. Sorry I find this sort of confusing
    best,
    Josh
     
  10. Pancakes

    Pancakes Friend

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    What's before the amp?
     
  11. Josh Schor

    Josh Schor Friend

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    schitt gungnir
     
  12. Josh Schor

    Josh Schor Friend

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    gungnir balanced into transformer box (you built) then to amp
     
  13. Josh Schor

    Josh Schor Friend

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    oh I get it the output inpedence of the Gungnir you say is arounf 7.5 so then is 50kohm or 100kohm or 250kohm best or does it matter
    best
     
  14. Pancakes

    Pancakes Friend

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    Gungnir should be 75ohms. So you want a minimum of 7.5 Kohm pot. 10K or 20K are generally available and will be fine.
     
  15. Beefy

    Beefy Friend

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    When did this rule become 100x? It's always been 10x for as long as I've been around. You can go even lower if the output impedance is linear, your cables are short, and your source can handle the current. The only consequence will be a small loss of voltage swing seen at the amp's input.

    In any case, 100k should be fine in just about every circumstance. Needing higher seems a bit nutty.
     
  16. Pancakes

    Pancakes Friend

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    Maybe it was 10X lol. My memory is garbage. Anyway, I always use 10k or 20k.
     
  17. Josh Schor

    Josh Schor Friend

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    I had always thought for tube amps 100kohm and up for SS amp 10 kohm. Is this an urban myth?
    Mine is a tube amp.
     
  18. Pancakes

    Pancakes Friend

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    It's not the amp that matters. It's the output impedance of the previous component.
     
  19. Josh Schor

    Josh Schor Friend

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    thanks for all of your help
    best,
    Josh
     

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