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Topic: Vol/tone pedal problems |
Tele
From:
Andy W. - Wolfenbuettel, Germany
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Posted 24 Feb 2000 1:19 pm |
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Hi
I have an old Bigsby pedal, theone which works on volume and tone. I have problems with the voulume pot since it doesn't work as smooth as I expect it. Its either full on or off but not so much in between.
Any suggestions? |
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Keith Hilton
From:
248 Laurel Road Ozark, Missouri 65721
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Posted 24 Feb 2000 4:19 pm
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Yes, get one with a logrithmic taper. You probably either have a linear or audio taper. These tapers come on quicker than a logrithmic taper. Logrithmic taper is what all steel guitar pots have in them. 500K Log taper pots are not standard items you can buy at a electronics store. Logrithmic is a mathematical term describing how the volume comes on in terms of a audio curve-----on a X---Y axis.
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[This message was edited by Keith Hilton on 24 February 2000 at 04:20 PM.] |
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db
From:
Bethlehem, PA 18015 USA
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Posted 26 Feb 2000 1:06 pm
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I have reconditioned three Fender volume tone pedals.
I installed a 100k-ohm stereo, dual potentiometer log taper.( RadioShack part # 271-1732)
(The rule of thumb is to have a pot that is 5 to 10 times greater DC resistance than the source impedance.)
They work very smoothly.
The two pots can be wired in parallel for more reliablity and a lower impedance.
They also have a 40% tap-point to connect a bypass cap (.001uf or less) for a flatter frequency response at the mid-point settings.[This message was edited by db on 26 February 2000 at 01:09 PM.] |
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Keith Hilton
From:
248 Laurel Road Ozark, Missouri 65721
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Posted 26 Feb 2000 5:49 pm
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db--I am familar with the Radio Shack 100K stereo pot. Always thought it was audio taper. Maybe I need to look at it again.
One thing that kind of confuses me--db--is why you would want to lower the input impedance buy wiring the 2 pots in parallel?With pickups, low impedance tends to milk off the highs. Seems to me a pickup sounds best run to high impedance. Maybe you like a lot of bass. Just kidding! db--do you run the .001uf capacitor to ground? That is one leg of the cap is attached to the tap, and the other leg is to the ground connection?
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db
From:
Bethlehem, PA 18015 USA
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Posted 26 Feb 2000 7:03 pm
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Keith,
Log taper = audio taper
Yes, it is best to have the load impedance greater than the source impedance.
Yes, if you go too low with the load (the total pot resistance) you will reduce highs.
Also, if you go too high (like 50X higher than the source) then you get high frequency loss in settings less than at maximum (at the point where the resistance from the top of the pot to the wiper becomes greater than the source impedance).
With a 500K pot this point happens almost immediately. A typical Steel guitar pickup is between 10k and 25k. So, an ideal load impedance would be much lower (50k to 100k).
The cap goes from the input or top of the pot to the 40% tap point.
This even further reduces any "series" losses.
But, the may reason I have the two in parallel is to improve reliability by reducing dropouts and pot wiper noise.
db
[This message was edited by db on 26 February 2000 at 07:09 PM.] |
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Keith Hilton
From:
248 Laurel Road Ozark, Missouri 65721
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Posted 26 Feb 2000 9:53 pm
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db--we are both probably correct. If you look in electronic parts catalogs at potentiomers, there are many audio tapers and many log tapers. Some people who make pots have went to using letters to indicate the taper. They show a diagram and call a certain slope a "B" taper or a "D" taper.
The Radio Shack pot you describe db,only costs $1.99. A regular 500K steel guitar pot ranges in cost from $22.00 to $26.00 Why don't some of you guys go to Radio Shack and buy this pot db suggest and report back? If it works, look at what you would save. db is sold on it.
db, have you ever tinkered around with putting capacitors between different terminals of a regular 500K steel guitar pot?
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db
From:
Bethlehem, PA 18015 USA
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Posted 26 Feb 2000 10:19 pm
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Yes, I have seen and tried a .001uf or 500pf cap from the input (or top of the pot) to the output (or wiper).
This is close to the same effect as the "tap cap".
You know, that $1.99 investment also gets you a lot of possibilities on how you can wire it up to customize it to work with your rig. [This message was edited by db on 26 February 2000 at 10:27 PM.] |
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Jack Stoner
From:
Kansas City, MO
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Posted 27 Feb 2000 5:56 am
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Keith, do you really want to use a Radio Shack pot?? There is a lot of difference in the construction and the electronic elements (thickness of the resistance element, etc) of the two pots. The Clarostat pot is overpriced, but the imported Radio Shack is no where close to the Clarostat in quality. Plus the Radio Shack pot is a metric size, which means the mounting is smaller and a metric thread. The Clarostat is a "Mil Std" pot.
I avoid Radio Shack parts like the plague.
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Keith Hilton
From:
248 Laurel Road Ozark, Missouri 65721
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Posted 27 Feb 2000 8:11 am
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Jack, I agree, you get what you pay for! I personally don't think the Radio Shack pot would make most steel players happy. It might work to some degree in the older Bigsby,and Fender volume tone pedals. I suppose if you are trying to re-create the sounds of the 40's and 50's, a Bigsby or a Fender volume pedal might be what you need.
I just don't see these pedals under any of the modern steels at shows, but I suppose there are still a lot of them out there. At the same time, I don't want to get "db" upset, because he is sold on the Radio Shack pot.
That's why I said for the guys to try it and report back.
Jack, you know what I like! I don't use "ANY" pot in my new infrared pedal.
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db
From:
Bethlehem, PA 18015 USA
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Posted 27 Feb 2000 12:07 pm
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The mounting threads are metric,
the shaft is STD 1/4".
I have found that all pots get noisy after a while, no matter what the "quality".
I prefer "open" pots so that one can periodically shoot in conditioner.
One cannot do this with the sealed "high quality" pots without complete disassembly.
It's a question of personal preference.
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Eric Stumpf
From:
Newbury, NH 03255
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Posted 27 Feb 2000 7:23 pm
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| So now that you've scared me with all this technical talk, who out there really can fix my Bigsby Vol/Tone pedal properly? The last two guys who tried, botched it. OK, three guys...I messed it up, too! |
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db
From:
Bethlehem, PA 18015 USA
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Posted 27 Feb 2000 7:41 pm
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Is there a RadioShack in Germany anyway?
I still recommend a 100kohm audio (log) taper pot.[This message was edited by db on 27 February 2000 at 07:42 PM.] |
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Tele
From:
Andy W. - Wolfenbuettel, Germany
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Posted 28 Feb 2000 11:26 am
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Well, some sort of Radio Shack but no pots like that. All I could buy are Fender or Gibson replacement pots.
I have a Clarostat in my Sho~Bud pedal and it's the best I found but these are very expensive and I only could get them vial mail order from the USA....
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Fender Dual Professional
Sho~Bud D-10 Professional |
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