maestro boomerang wah- info, innuendo and inference
Posted: Sun Jan 15, 2012 8:09 pm
a few findings on boomerangs, inspired by the wacka thread:
i can say definitively that a hotpotz 1 or 2 with a 33k resistor ( or any other limiting resistor) will not sound, sweep or react like a correct 25k pot.
my findings after a few years of boomerang obsession. richard mintz, whose company built all of the boomerang2s, told me that the original spec was even a little different than a standard reverse log. he also was adamant that the higher value pot with limiting resistor was not going to interact with the circuit correctly.
before he told me this, i had previously done hundreds of experiments with dozens of pots in real boomerangs, and boomerang clones in CB cases. also bought a couple dozen 25k,30k, 50k pots from ebay and surplus places trying to find a suitable replacement. none of my experiments yielded a feel like the original. ( PEC does make a rev log 25k rv4 spec pot, which is next on my list to try, around 12 bucks from digi-key)
we have in our collection a real 67 BG1, ( sounds best of any i have heard ), a half dozen BG2s, and have sold quite a few 2s as well.
it is exceedingly rare to find a BG of any vintage with a non-scratchy original pot. when i finally found a bg2 with the original pot, i was blown away. not only did the wah sound closer to our holy grail 67 than any other, the volume pedal function actually works beautifully. it actually gives a slight boost in vol mode, and sweetens the tone. mintz had been telling me for a couple years that a correct bg2 will not suck tone in bypass, i finally found for real what he was talking about. you can hear the wah sound of this 100% original non scratchy bg2 here:
back to the sweep question. the reason that a hotpotz2 ( or hotpotz1) will not give the correct reaction is that the taper has a fast kink in the sweep. this is why some people prefer the more gradual icar. when you put a limiting resistor across this quick ramp, it simply condenses the ramp, making it even worse! i went so far as to fabricate offset cam type gears to try and slow down the ramp on a hotpot ( hotpotz 1 and 2 have same taper BTW). it got close but then required a spring load pusher for the straight gear to keep it on the gear! and again, the limiting resistor changed the tone vs the stock comparison unit.
when measuring the actual resistance of the original 25k pot while in the actual boomer case, the reaction is very close to linear.. imagine that, they had to use a log to simulate linear, due to the physics of the rack gear! what is funny, is that an icar does something quite similar, although not quite as linear.
so, some wah guys have mentioned they like icar with limiting resistor for boomer, which helps, but most icars are closer to the original 180k, which again moves us in the wrong direction.
one more wrench to throw into the monkey farm:
if you build a boomer clone in a CB case, you have a slightly shorter throw, and the pot is running opposite direction, making all of the specs for std boomers backwards regarding taper. so if you build a boomer clone in a CB/vox case, try a 25k log ( PEC as mentioned above)
in an attempt to get a hotpotz1 or 2 to work correctly in a boomer clone in CB case, i worked up another non-concentric cam-like mechanism that gets me as close as anything i have tried so far- a clone in CB/vox case
you might be wondering, why does a quicker taper matter?, i can just adjust my foot action. it is possible you could be this accurate, but the beauty of a boomerang is the super extended play area across the mid hump sweet spot, as heard in jj cale's crazy mama. boomers are popular with swamp guys too because of this ability to ride the sweet spot in detail.
there is a tone and electronic component to all of this that few have considered, but one that in my research seems to explain why a slower taper also effects the tone. an inductor wah is constantly charging and discharging a cap to ground off the inductor. think of it like filling and emptying a bucket. if the ramp is too fast, or the resistance on either side of the two sided pot equation is too low ( think of the narrow or wide slope shape of Q on a parametric), the cap may never get to a full charge as it passes across. just a theory i am working on.
that's the gist of what i've found so far. i have approx 20 or 30 youtube vids on my channel relating to boomers, check em out!
i can say definitively that a hotpotz 1 or 2 with a 33k resistor ( or any other limiting resistor) will not sound, sweep or react like a correct 25k pot.
my findings after a few years of boomerang obsession. richard mintz, whose company built all of the boomerang2s, told me that the original spec was even a little different than a standard reverse log. he also was adamant that the higher value pot with limiting resistor was not going to interact with the circuit correctly.
before he told me this, i had previously done hundreds of experiments with dozens of pots in real boomerangs, and boomerang clones in CB cases. also bought a couple dozen 25k,30k, 50k pots from ebay and surplus places trying to find a suitable replacement. none of my experiments yielded a feel like the original. ( PEC does make a rev log 25k rv4 spec pot, which is next on my list to try, around 12 bucks from digi-key)
we have in our collection a real 67 BG1, ( sounds best of any i have heard ), a half dozen BG2s, and have sold quite a few 2s as well.
it is exceedingly rare to find a BG of any vintage with a non-scratchy original pot. when i finally found a bg2 with the original pot, i was blown away. not only did the wah sound closer to our holy grail 67 than any other, the volume pedal function actually works beautifully. it actually gives a slight boost in vol mode, and sweetens the tone. mintz had been telling me for a couple years that a correct bg2 will not suck tone in bypass, i finally found for real what he was talking about. you can hear the wah sound of this 100% original non scratchy bg2 here:
back to the sweep question. the reason that a hotpotz2 ( or hotpotz1) will not give the correct reaction is that the taper has a fast kink in the sweep. this is why some people prefer the more gradual icar. when you put a limiting resistor across this quick ramp, it simply condenses the ramp, making it even worse! i went so far as to fabricate offset cam type gears to try and slow down the ramp on a hotpot ( hotpotz 1 and 2 have same taper BTW). it got close but then required a spring load pusher for the straight gear to keep it on the gear! and again, the limiting resistor changed the tone vs the stock comparison unit.
when measuring the actual resistance of the original 25k pot while in the actual boomer case, the reaction is very close to linear.. imagine that, they had to use a log to simulate linear, due to the physics of the rack gear! what is funny, is that an icar does something quite similar, although not quite as linear.
so, some wah guys have mentioned they like icar with limiting resistor for boomer, which helps, but most icars are closer to the original 180k, which again moves us in the wrong direction.
one more wrench to throw into the monkey farm:
if you build a boomer clone in a CB case, you have a slightly shorter throw, and the pot is running opposite direction, making all of the specs for std boomers backwards regarding taper. so if you build a boomer clone in a CB/vox case, try a 25k log ( PEC as mentioned above)
in an attempt to get a hotpotz1 or 2 to work correctly in a boomer clone in CB case, i worked up another non-concentric cam-like mechanism that gets me as close as anything i have tried so far- a clone in CB/vox case
you might be wondering, why does a quicker taper matter?, i can just adjust my foot action. it is possible you could be this accurate, but the beauty of a boomerang is the super extended play area across the mid hump sweet spot, as heard in jj cale's crazy mama. boomers are popular with swamp guys too because of this ability to ride the sweet spot in detail.
there is a tone and electronic component to all of this that few have considered, but one that in my research seems to explain why a slower taper also effects the tone. an inductor wah is constantly charging and discharging a cap to ground off the inductor. think of it like filling and emptying a bucket. if the ramp is too fast, or the resistance on either side of the two sided pot equation is too low ( think of the narrow or wide slope shape of Q on a parametric), the cap may never get to a full charge as it passes across. just a theory i am working on.
that's the gist of what i've found so far. i have approx 20 or 30 youtube vids on my channel relating to boomers, check em out!