Changing a linear taper volume pot to audio taper affects tone?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by DonaldDemon, Mar 3, 2015.

  1. DonaldDemon

    DonaldDemon Member

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    I have a Roccaforte Custom 80 coming and it most feedback I read states the master volume doesn't work well because of the linear taper pot. The builders description says "The master volume, if used, is for darkening the tone and adding a little dirt at lower volume settings."

    Seems like the MV doesn't work on the traditional sense. Will changing this pot to an audio taper make the master more usable and what affect might it have on the tone, if any? My Splawn works the same way in that the volume is tricky to set a decent level, something that he fixed on later models.
     
  2. TimmyP

    TimmyP Member

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    There should not be a tone change. An audio pot should make the control less difficult to use - at least in a normal circuit application. A linear pot will normally be about 6dB down at half rotation, so most all of the action takes place from half to off, making it touchy. An audio pot will be about 20dB down at half rotation, so the action takes place from 7/8 to 1/4 - much smoother control.
     
  3. teemuk

    teemuk Member

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    Resistance is resistance, no change due to that. If pot's resistance remains the same and only the tapering function changes the resistive divisions also remain the same and henceforth all RC or LC filters introduced by the circuit too. The taper just dictates the function in which the division of resistance from terminals of the resistive strip to wiper changes within rotation of the dial: With linear pot you have 50-50% division at middle, with logarithmic pots you commonly have either 10-90% or 30-70% division in the middle (depending on taper type). Since increments in resistance are small in the beginning of the dial and high in the end of the dial the human's perception of loudness, also logarithmic, is tracked more accurately than with linear pot. But resistive states don't change, they just follow a different "taper".
     
  4. DonaldDemon

    DonaldDemon Member

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    Good to know, thanks for the responses. Makes me wonder though, why do builders use these linear pots, especially on the most sensitive control such as a master volume, when they know it makes it more difficult to dial in? Assuming you know how to design a circuit to build an amp, what would be some reasoning for using those in place of the favored log pot?
     
  5. J M Fahey

    J M Fahey Member

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    Price and availability.

    Not forgetting that Linear master pots provide the "hey!!! see how loud it's on 1, I bet by 6 it will bring the roof down" thing, or lots of Forum comments such as: "xxx amp is too loud!!!!" .
     
  6. jay42

    jay42 Member

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    I would be more interested in what type of MV circuit it is. Dual-ganged 1M Linears are easier to source than log taper parts.m that would infer Post -PI.

    PS. Whaddup wit the Roccaforte website?
     
  7. DonaldDemon

    DonaldDemon Member

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    I kind of doubt builders want the reputation of amps being too loud these days, especially when everyone is trying to keep volumes down.
     
  8. DonaldDemon

    DonaldDemon Member

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    Yeah I have no clue about that stuff. Someone here could probably answer better as to what kind of MV circuit Splawn or Roccaforte use. I think Doug Roccaforte gave up on dealing with the public and only caters to "industry professionals" whatever that means. I'm not sure if he is even still making amps any longer, haven't seen new ones floating around much these days
     
  9. Blue Strat

    Blue Strat Member

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    ^^^ Reminds me of a funny line I read on the Fender Discussion Page years ago. "If I had to make a living dealing with amateur musicians, I'd kill myself". :D
     
  10. DonaldDemon

    DonaldDemon Member

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    Ha yeah I get it, especially after some of the nonsense I see here. :crazy

    But...you just cut off 99% of your customers, guess he just doesn't want to be in the game anymore.
     
  11. Blue Strat

    Blue Strat Member

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    Yeah, I imagine he really wanted to limit production. Definitely not a growth move.
     
  12. upright1

    upright1 Member

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    My Vibro King had a linear taper pot for volume. It went from off to LOUD real quick. I had my tech install an audio taper. It is now much more usable.
     
  13. J M Fahey

    J M Fahey Member

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    ^^^^^^ that's the point.
     

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