adding a fine rate or speed control pot to a modulation effect

[petey twofinger]

i would like to add a " fine " rate or speed control to a few of my modulation pedals .

i rehoused a danelectro chicken salad  , that uses a dual 100k B pot wired as a variable resistor , not a voltage divider ( only 4 lugs are used on this "stereo" pot) ,  for the rate . i tried a dual 500 ohm linear in in series and parallel with the stock 100 k b rate pot and it did not function . there was either no effect or it ran at its high end rate , because it was only seeing 500 ohms at that connection .

the 100 k pot on the chicken salad is too sensitive for me to be able to use it to roughly " sync " it to tempos of 100 to 120 bpm songs , as a slight nudge and it rockets about 10 bpm making it a bit frustrating and time consuming .

i searched the forum . i searched google , i searched for schematics for a pedal that feature a second "fine" rate or speed control . the only thing that i could find  , was a roger mayer voodoo vibe . i found a four page schematic , that did not give me any hint as to why what i tried to do did not function . i understand the path of least resistance theory , i think , i guess i do not . i figured in my ignorance that path of least resistance would only be  a negative factor in attempting to achieve my goal when the parallel wiring of two pots was implemented  . the series set up i tried was as follows , the 100 k b stock pot after the 500 ohm B dual pot . with this configuration the effect did not modulate at all i am guessing because of some massive child like oversight or simple error due to my ignorance and staggering lethargic slothitude .

i will spend more time with this tomorrow or in the decades that lay ahead . if i figure it out before i cease to exist, i will more than likely consider posting how i pulled it of as it seems like this effect is a good candidate or a rehouse , and mod , but prolly not .  i would also like to implement this fine control on a few pedals i have here as it seems like a useful mod to me . but what do i know about this rock and roll business anyway ?

[samhay]

As an alternative, would a 100k (reverse) log pot work any better?

Edit - found a schematic: http://www.experimentalistsanonymous.com/diy/Schematics/Vibrato%20and%20Pitch%20Shift/Dan-Electro%20Chicken%20Salad.gif
Looks like a smaller dual pot should work if each half of it is wired in series with the existing pot - is this what you tried? 

[nocentelli]

Just look at the original schematic for the tremulus lune: It has a course rate control (10kB) in series with a fine rate pot (1kB). The smaller the overall resistance, the faster the rate: The large pot gives a wide range of resistance, with less precision, the smaller pot gives a much smaller range of resistance but with much more precision.

An alternative is to use a reverse log pot (as mentioned) or cobble one together with a larger value pot than you need and a fixed parallel resistor across the outer lugs to give the appropriate total value. The slower rates (greater resistance) have a shorter travel, and as you reach higher speeds (where it is harder to set the exact rate), the resitance change becomes more spread out. 

[GibsonGM]

Just look at the original schematic for the tremulus lune: It has a course rate control (10kB) in series with a fine rate pot (1kB). The smaller the overall resistance, the faster the rate: The large pot gives a wide range of resistance, with less precision, the smaller pot gives a much smaller range of resistance but with much more precision.

An alternative is to use a reverse log pot (as mentioned) or cobble one together with a larger value pot than you need and a fixed parallel resistor across the outer lugs to give the appropriate total value. The slower rates (greater resistance) have a shorter travel, and as you reach higher speeds (where it is harder to set the exact rate), the resitance change becomes more spread out. 

+1   This setup works pretty well, at least for me.

[Mark Hammer]

In LFOs, faster speeds come with smaller resistance, such that the relevant caps charge up faster.  The problem with any speed control that attempts to achieve something like a 10:1 (or greater) speed range, is that no matter what sort of taper you use, some speeds, whether slow or fast or in between, are going to be bunched up.

For me, the "solution" is to use the stock dual pot, and use a DPST toggle (or DPDT on-off-on if that floats yer boat) to strap a fixed resistor across the pot sections to turn it into what amounts to a smaller-value pot.  A 39k strapped across the pot makes it equivalent to a 28k pot, and a 10k strapped across it makes it equivalent to a 9k pot, which ought to get you suitable dialability for medium and faster speeds.

[duck_arse]

or switch-change the timing cap value.

[Mark Hammer]

Not that sort of LFO.  I think it would require changing 3 caps.

[petey twofinger]

ty very much yall ... monkey time will comence immediately .

[Dreverb]

For me, the "solution" is to use the stock dual pot, and use a DPST toggle (or DPDT on-off-on if that floats yer boat) to strap a fixed resistor across the pot sections to turn it into what amounts to a smaller-value pot.  A 39k strapped across the pot makes it equivalent to a 28k pot, and a 10k strapped across it makes it equivalent to a 9k pot, which ought to get you suitable dialability for medium and faster speeds.

Hello all. Please. Could it be possible to explain this a little??? I would love to add a fast/slow switch on my chicken salad. Thanks anyway