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Topic: Short throw on volume pot |
Frank Parish
From:
Nashville,Tn. USA
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Posted 9 Jul 2006 7:02 am |
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| I recently bought a couple of the old A&B linear taper pots for my old Emmons pedal. The tone is great as usual but I can't set it to open the pedal all the way without the volume being very loud in the up position. I like to hear it just a little to tune with and not all the way off. Is it the taper that's causing this? The only solution I can think of is to find a smaller wheel to wrap the string around but where can I find that? Who makes these things? I've got a couple of the top of the line electronic pedals but I want this for the practice room and also sometimes it's just convenient to not have to plug so much stuff up. I carry two pedals and the Emmons pedal is one I want to carry. |
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Donny Hinson
From:
Glen Burnie, Md. U.S.A.
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Posted 9 Jul 2006 4:34 pm
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Frank, are you using the "open-type" Emmons pedal? It's one of the poorest ones out there. But if you like it, I suppose you could have a smaller spool made, or you could modify the pedal to get a little more travel. Personally, I'd just set up the pedal so it gave me what I wanted in the off position, and not worry about not having "full on" capability. Opportunities to go "full on" aren't many, and besides...you're only getting "full on" anyway if your amp volumes are maxed out.
Turn your amp up and forget that little bit of rotation you're losing with that pedal. |
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Mike Wheeler
From:
Delaware, Ohio, USA
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Posted 10 Jul 2006 4:43 am
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Frank, part of your problem is the linear taper. Linear taper means as the pot is rotated, the signal change equals the pots percentage of rotation. 50% rot. = 50% signal The rate of signal change is constant throughout the pots travel. It's not natural sounding when used as a volume control.
Log taper (or the similar audio taper) is what you need. With it, the signal change matches, more closely, what your ear perceives as the loudness level, or volume. 25% rot. = 1/4 of the available loudness, 75% rot. = 3/4% of the available loudness. The rate of signal change is smaller at the beginning of rotation, and becomes greater toward the end of rotation.
Hope this helps...been a long time since I thought about this stuff.
EDIT: I mis-spoke...The rate of SIGNAL change is larger at the beginning of rotation, and becomes smaller toward the end of rotation.[This message was edited by Mike Wheeler on 10 July 2006 at 08:17 AM.] |
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Bill Crook
From:
Goodlettsville, TN , Spending my kid's inheritance
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Posted 10 Jul 2006 6:29 am
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Mike................
While not wishing to start any kind of war here, A lot of you players have the wrong concept of the two different pots.
A linear taper is just that:
It means that the volumn is increased at a 45 degree angle,from 0 to 100% level.
A audio-taper is:
the volumn is increased up to about 50 or 55%. Then it is almost constant thereafter.
The audio-taper control was designed for and first used in radios. As radios do not generally sound good at low volumnes, the indrusty designed a pot to boost the lows and present a somewhat better sound.
For you techs.........
Measure the difference beween the two types of devices and you will see what I'm refering to.
The misconception of this device is why many of you do not get the desired results from your "pot-pedals".
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http://home.comcast.net/~crookwf/
http://photobucket.com/albums/v479/billcrook/
[This message was edited by Bill Crook on 10 July 2006 at 07:30 AM.] |
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Mike Wheeler
From:
Delaware, Ohio, USA
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Posted 10 Jul 2006 7:10 am
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Bill, the construction of the pots in question are linear or log. A pot is a variable resistor and cannot, by itself, change the frequency response of a circuit.
What you refer to (that was used in the old radio circuits) was a "loudness control" and was one part of an interactive circuit which allowed for an increase in low frequencies at low volume (to compensate for the human ear's lack of sensitivity at lower frequencies). A volume control for a steel guitar does not require this function.
When a pot is used as a volume control in a volume pedal, the only interaction (basicly) is with the pickup. (pickup loading by the pot aside) Controlling the voltage from the pickup is it's primary function.
In this roll, a pot's taper characteristics are it's most important feature. A linear pot changes resistance from it's lowest to highest values in a straight line, 45 degree angle (as seen on a graph of resistance versus output voltage). A log pot's graph will show a logarithmic curve under the same test procedure.
Because of the way the human ear perceives sound, the log pot will change the volume of the sound in a more natural way than a linear pot does...that is, turning the pot halfway up provides a volume of sound that is perceived as half of the total sound volume available. If you'll remember your decibel calculations, you'll remember they involve logarithmic calculations.
If I'm not being clear enough, I'm sure there others who could elaborate further....this is too much thinking for someone my age.[This message was edited by Mike Wheeler on 10 July 2006 at 08:12 AM.] |
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John Daugherty
From:
Rolla, Missouri, USA
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Posted 10 Jul 2006 12:05 pm
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Mike, You got it right. Couldn't have said it better if I ate 12 bowls of "Total".
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www.home.earthlink.net/~johnd37
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Bill Crook
From:
Goodlettsville, TN , Spending my kid's inheritance
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Posted 10 Jul 2006 12:58 pm
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Mike......
I agree with you 97% !!
In the post above this one, (How Much Power is Enought) much is discussed about loudness and sustain. My thoughts for useing a linear pot is mostly due to the sustain reason.
| Quote: |
| turning the pot halfway up provides a volume of sound that is perceived as half of the total sound volume available. If you'll remember your decibel calculations, you'll remember they involve logarithmic calculations. |
Now,if we have the pedal (useing audio-taper pot)at 1/2 volumn,the last half of the pot responce is generally flat. That means we canot raise the volumn level much more to keep the sustain going. We hear a lot players dissing brand X or brand Y Steel Guitar because of poor sustain abilities. It may not be the Ax, It more likely is the device in the pedal.
Watch the players foot as he holds onto a long note, As the sound begins to die out,He pushes down on the pedal to increase the volumn level. Useing a linear pot,he has about 50% more sustain time because he has not reached the flat top half of the volumn avalable to him.
I think we have a great discussion going here. Maby we can get a few more to chime in with us. I feel that these two post about pots and power should help inform many in the Steel Community.
I canot comment about useing a "Hilton Pedal" or other electronic controllers as I have never had the oppertunity to play with them. I do see a lot of "Pros" that use em' but I am not a pro player and canot afford to purchase one.
This power vs speaker vs pot discussion is really good !! Very informative to me and others.
Lets keep it going,clean,and fun without dissing anyone for his thoughts or ideas. I'm sure there are others out there that have an opinion about these subjects. Lets hear from you guys.
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http://home.comcast.net/~crookwf/
http://photobucket.com/albums/v479/billcrook/
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Mike Wheeler
From:
Delaware, Ohio, USA
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Posted 10 Jul 2006 3:52 pm
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Hi again Bill,
I never have and never will "dis" anyone intentionally. Lord knows I have had my share of honest mistakes so I give lots of leaway to others.
Regarding the pot discussion...(OK you young guys, not that kind!) The issue, as I see it, centers around how a human interfaces with the volume control. Meaning, when I turn the control, what do I expect to have happen? Well, it is usually marked with numbers 1 through 10. If I turn the knob up to 10 I expect to have the maximum. But what if I turn it only to 5? I think most would expect the result to be half of the maximum. But, the maximum of what??? Voltage, power, volume??
Here's where the confusion enters in...for instance, if I am using a voltmeter, looking only at the voltage output from the pot I might want to see half the voltage at the wiper when I've turned the pot to it's midpoint...if so, I would want a linear pot.
But, (i love buts, don't you?) what if the pot is controlling a sound source and I want to hear the SOUND turned up to half of the maximum available level? (now, here's the catch) If I use a linear pot, I'll get half of the output VOLTAGE level available from the system, but NOT half of the sound output. If I use a logarithmic pot, at the midpoint I'll get half of the sound ouput from the system, but somewhere around 70% of the voltage available. This is where Decibel calculations come into play. (I'll leave those to one of our fine engineers to explain)
You see, humans percieve sound pressure levels in a non-linear fashion, ie; logarithmically. In order to make a sound twice as loud, the power applied to the source must be doubled...to make it twice as loud again, the power must be doubled again, and so on and so on.
In the case of a volume pedal, we have a slightly different usage. It's being used to set a starting volume level and then, by turning it up, an attempt is being made to maintain, or sustain, that volume level. The logarithmic pot is ideal for this purpose, because most of it's volume increase happens in the last half of it's travel, logarithmicly. This provides a nice "feeling of sensitivity". The linear pot would require a much greater amount of travel to accomplish the same thing, and thus would "feel" awkward.
I'll leave it to the other more astute guys to provide the formulas and details regarding Decibels and Power relationships, if anyone wants them. It's been over 20 years since I've had to deal with this stuff and the old memory is straining. I could look it up, but I'm also lazy nowadays. ;-)
I sure hope this didn't confuse anyone...it's a tuff subject to explain...took me years, and several books, to understand.
Edited for clarity...yeh, right!! lol[This message was edited by Mike Wheeler on 10 July 2006 at 04:58 PM.] |
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