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Why Audio Taper Pots Instead of Linear Taper?

Discussion in 'Tele-Technical' started by bottomfeeder, Jan 17, 2013.

  1. bottomfeeder

    bottomfeeder TDPRI Member

    56
    Oct 15, 2010
    Newport News, Virginia
    Just wondering why almost all electric guitars are manufactured with audio taper pots.
     
  2. waparker4

    waparker4 Doctor of Teleocity

    Nov 9, 2011
    Philadelphia, PA
    They are called "audio taper" because they work for volume controls, the volume seems to increase gradually. Linear seems to be all the way up early on in the dial and the rest doesn't do much. The ear doesn't perceive twice the signal intensity to be twice the volume. It's a logarithmic relationship, and audio pots are also called log taper.

    And as far as the rest of the controls, it's probably cheaper to use all the same type of pot rather than mix and match.
     
  3. jefrs

    jefrs Doctor of Teleocity

    Nov 20, 2007
    Newbury, England
    Linear turns down gradually instead of going for all-on to practically silent like an audio pot. I notice players with audio pots set them at 10 and never roll back the knob.

    Fender do fit audio, but Gibson have used Linear for volume.
    I retro-fit with linear vol for better usability.

    Always audio/log for tone control though except a few odd-balls like jazzmaster.
     
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  5. bottomfeeder

    bottomfeeder TDPRI Member

    56
    Oct 15, 2010
    Newport News, Virginia
    Sounds like two opposing views
     
  6. Wally

    Wally Telefied

    Mar 17, 2003
    Lubbock, TX
    Teh engineers will tell you that the audio 'fits' the human ear better, IN practice, I agree with what jefrs has to say. An audio pot loses its 'presence' and usability at 7. From there on down, the pot sweep is of no use, ime.
    a linear voluem pot does come 'on' at about 2. I disagree that the rest of thesweep is of no use. There is a gradual increase of voume on up the dial, and the entire sweep of the potis useflul. IT may be that one woudl need to turn an amp up a bit to hear this, but that is the way I run an amp anyway. I set my gutiar controls at 10 and set the amp up for the max amount of voume and/or distortion that I wnat....adn run thigns from the pot on the gutiar. A linear voluemcontrol will yield different levels of usable voume from 10 on down to around 2. An audio pot will die at 7, and the singal is too think to be of much use on down the sweep.
    bottomfeeder, thisis an aspect of the qeustion you posed in your other thread "SEriesWrirnig question".... What you were inquiring about is called a treble byass circuit...or treble bleed circuit. IT is used on audio taper volume pots to widen the usable sweep of that audio pot....to maintain presence below 7. IT is interesting when you get into treble bypass circuits. Different capacitance and different resistances yield different results with different pickups. I am of the opinon that one needs to 'tune' the treble bypass circuit to the picku0p. For instance, ime, the 'standard' .001mfd cap that FEnder installed in the 1968 TEles is not a good choice. I have found that for single coil pickups, larger capacitance and ad added ressitr yields a better taper and tone.
    FWIW,
    fender started addressing the 'problem' of the limited sweep of an audio taper voume pot on guitars in 1968. Gibson, as jers notes, started using
    300K linear taper pots in 1973 or so, IIRC, in order to give gutiarists the ability to dial in different usable outputs from their guitars. One can go from clean to distorted and control dynamics wtihmore subtlety (?sp?) with a wider sweep on that volume pot. OF course, Gibson first addressed this issue in the 1950's with what is called the '50's wiring circuit in Les Pauls. They took a different route of wiring in the tone cap, and that circuit changes the taper of the volume pot as well...just not as greatly as a linear pot or the treble bypass circuit, ime. (In 1968, Fender was probably trying to find a way to do what Gibson had done 10 years before....just don't tell anyone here on the TDPRI that I said so, okay? LOL ) OF course, Gbison didn't keep wiring guitars with that '50's circuit, did they? Tehy on ly did that for a few years.
     
  7. jefrs

    jefrs Doctor of Teleocity

    Nov 20, 2007
    Newbury, England
    I set my amp up to maximum volume for the occasion, or perhaps a little more, with the guitar linear volume knob a little below 5. But with a linear pot this is not 50% volume, it is more like 80-90%

    I set up with the knob at half way and I will want a 10% to 20% volume increase for a lead break, this is equivalent to rolling a linear up from just below 5 to 10. A greater volume increase than that can throw the stage mix out of kilter.
    I do not need to double the volume, besides I can control dynamics with my fingers: if I want quiet, I play soft.

    If I need more volume than that I can stomp a pedal or swap channels.

    I prefer to have the amp set a little too loud and bright, I can drop the volume and tone at the guitar, but if there is not enough volume you have to go groping for the amp knobs ...
     
  8. Vizcaster

    Vizcaster Friend of Leo's

    Sep 15, 2007
    Glen Head, NY
    RS Guitarworks makes a hybrid taper that works very well. This is only really important if you're playing with a serious quantity of distortion on your amp, and then you can change the gain right from your guitar volume knob.
     
  9. Rod Parsons

    Rod Parsons Friend of Leo's

    Age:
    69
    Sep 26, 2009
    Winchester, Va.
    With an audio pot, where it gets loud or quiet really fast on the dial, [and not gradual like a linear pot], a guitar player can have an easier time with volume or tone swells by using his or her pinky to turn the knobs. The knob only has to turn a small amount to make a more radical difference in tone or volume for the pedal steel guitar sounds. Most players who do this prefer the audio pots, I do believe.
     
  10. dadder

    dadder Tele-Meister

    211
    Sep 10, 2011
    Northern Ireland
    Generally speaking, log/audio taper pots for vol, Lin. pots for volume.
    This will give the impression of a gradual increase in volume as you turn the knob from zero up to ten. As stated, this is just the way we hear it, not the way it really is. But, we are only humans after all, so, what we hear is what we want.
    I like 500k log for vol. and 250k lin for tone. BUT... sure as eggs is eggs, someone will disagree.
    All I can advise is, try different pots yourself and see what you prefer. They ain't that expensive and easy enough to swap about. When you've got it sorted, maybe you'll come back and let us all know how you got on.
    By the time you've finished, you'll be an expert.
     
  11. jefrs

    jefrs Doctor of Teleocity

    Nov 20, 2007
    Newbury, England
    ^^^ I think that might be log/audio or linear pots for volume, but log/audio pots tone.

    Tone pots are always log/audio. Rolling down a linear tone pot goes: bright, bright, bright, bright, bright, bright, bright, mud
    At 5 a log pot is at 1/10th its full value and is a usable setting for tone, this occurs at 1 on a linear pot.
    At around 8 a log pot is around 1/2 its full value and is usable setting for tone, this occurs at 5 on a linear pot.
    All you do with a linear tone pot is compress all its useful range into the bottom end of travel. Whereas a wide range of control is wanted. That's why they fit log/audio pots for tone controls on the vast majority of electric guitars.
    Some odd-balls like the jazzmaster roller-wheel does use a 50k Linear with a 1M Lin vol (its normal tone knob is a typical 1M Log with a 1M Lin vol)
     
  12. Rod Parsons

    Rod Parsons Friend of Leo's

    Age:
    69
    Sep 26, 2009
    Winchester, Va.
    Don't you have the names switched.. A linear pot is at 50 per cent volume, there about, at 5 on the tone control. It's the Audio pots that come on all at once.. The word linear means 1=1 in volume or tone.... 2=2, 8=8 10=10, et al.
     
  13. dsutton24

    dsutton24 Poster Extraordinaire

    Dec 29, 2010
    Illinois
    No. Linear refers to the fact that the resistance changes proportionately with the pot's shaft position. The human ear is not linear, and audio taper pots are a hybrid that sort-of mimics the way the ear works.

    As for what and where, use what you like. I generally use audio taper pots for both volume and tone controls.
     
  14. Rod Parsons

    Rod Parsons Friend of Leo's

    Age:
    69
    Sep 26, 2009
    Winchester, Va.
    I've been confused over this for years.. I get one answer that says one thing, then another that says something else. I assume that my '91 American Standard Tele has stock audio taper pots, right. They do kind of come on fairly smooth??? However, My 1980 Princeton Reverb comes on very loud before the dial even says #1. At home, I have trouble getting the right volume. At #1 on the dial, the volume is much too loud, at 1/2 on the dial it's not loud enough. It needs to be 3/4s of the way to #1. And it is very loud on 1.5 on the dial.. So is this the 'linear taper pot or audio. According to your explanation it would be a linear pot, right?. But I felt sure that they came stock with 'audio' pots... ???... I have heard the opposite of that from members on this forum too. I guess I'll just have to Google for more info. Thanks..:D:D:D
     
  15. Rod Parsons

    Rod Parsons Friend of Leo's

    Age:
    69
    Sep 26, 2009
    Winchester, Va.
    I just went online and read the definition of audio and linear pots, and you are right . I'm wondering now what volume pot is in my Princeton Reverb... Why does it come on so loud at one on the volume dial???
     
  16. jefrs

    jefrs Doctor of Teleocity

    Nov 20, 2007
    Newbury, England
    No, I was very careful not to mix up "value" and "volume" and when referring to the control I said things like "vol pot".

    I was also only referring to the common or garden 10% log pot, you can also have 20% and 30% lot pots, and a variety of hybrid Log/Lin things.

    However log pots consist of four linear tracks stitched end to end, so they only approximate a logarithmic taper in the first place. That also means the linear pot has no sudden jumps in it and less likely to produce scratchy sounds when worn.

    For me the knob on the guitar is all about ease of use, I do not need it to be proportional to the output volume (SPL). When I've had a log/audio vol pot there, I've never rolled it back below 7. With a linear pot I can dial it down to 2 and still be audible, if it's needed.

    With the tone pot things are a little different. For a start it is not used as a potentiometer but as a variable resistor in series with a capacitor in parallel across the pickup (an inductor and generator). For me, on a tele, a 250k log tone pot gives a usable range from 10 down to zero.

    Like I said in an earlier post YMMV - most folks are quite happy with the stock log/audio vol pot.

    Does this help?
    I can't find any log tables so I did it in my head, hence big gaps.
    ## - Lin - Log
    10 - 250 - 250
    09 - 225
    08 - 200
    07 - 175
    06 - 150
    05 - 125 - 25 (log pot is 1/10 or 10% of full value at 5)
    04 - 100
    03 - 75
    02 - 50
    01 - 25 - ~3 (log pot is theoretically 1/10 of value of "5" when at "0.5)
    00 - 0

    and 125/250 = 1/2 = half = 50%

    Due to the construction of a log pot track the first section up from zero is going to be a shallow gradient linear "taper". The top end of the pot however is going to be a very steep drop down from "10". So as soon as you nudge that knob away from 10, you notice a significant drop in volume: all that happens with a linear pot is you lose a little top end frissance at "9", the drop is less steep.
     
  17. dsutton24

    dsutton24 Poster Extraordinaire

    Dec 29, 2010
    Illinois
    The volume control is (probably) a 1 Meg audio taper pot, but it's very possible that the amp has been technicianized in the past.

    There's a thread running here that shows a chart comparing the two types of pot. What you describe is what you get with a linear taper pot in an audio circuit, abruptly loud near the bottom of the volume knob's range, then painfuly gradual change from the midpoint upwards. Like I said, some people like it that way, but it makes it hard to turn it down when you need to.
     
  18. jefrs

    jefrs Doctor of Teleocity

    Nov 20, 2007
    Newbury, England
    The volume pot in an amp is a true voltage divider. If it is too loud at "1" then it has not divided the voltage enough. The only way to fix that is to fit a bigger value pot so that "1" is a small ratio to the full "10" value, one way to so that is to use a log pot but even then the pot may not have enough span: use a larger value log pot.

    The vol pot in an amp is usually after the first gain stage so losing the small input signal through a some resistance is no longer a problem.

    At the same time also look at the DC blocking capacitor on the anode of the gain stage. There must be a DC blocker or you get HT on the grid of the next valve stage (very bad thing). But the value and type of capacitor can be a bit arbitrary, it can be a tone sucker especially when combined with a high value vol pot following it.
     
  19. Rod Parsons

    Rod Parsons Friend of Leo's

    Age:
    69
    Sep 26, 2009
    Winchester, Va.
    Thanks.. I bought the amp as a demo model and it has the original pots.. So it must be as you said... The one meg audio taper. It doesn't bug me,.... it is just something that I have always wondered about.. It has become something I brag about for kicks. I tell people how powerful it is and just turn it to one and it is LOUD.. :D
     
  20. Rod Parsons

    Rod Parsons Friend of Leo's

    Age:
    69
    Sep 26, 2009
    Winchester, Va.
    Thank you for your detailed explainations.. I have always been a little mixed up over the two types. :D
     
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