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High Cutoff Frequency Knob


Okay, so I was curious what values the lines on the BKs high pass filter knob actually might be to have a better sense of what I might be doing and not have to rely on quite as much guesswork. I emailed Guitammer/Buttkicker and they told me that they don't know what the values for each line are. While I find that hard to believe I can't think of any reason to not disclose that information.


I don't understand the math behind crossover filter circuits, but recognized that the trend was logarithmic. So through trial and error I came up with a curve that fit, actually two. Perhaps someone that actually understands this stuff can come up with a formula that actually represents what is going on in the circuit - maybe my formulas will look familiar enough that someone can easily get it just right.


Knob line.......1......2......3......4.....5.......6.....7......8 ........9.....10.....11

Printed Hz.....40............50...................70................ ....110...........160

My estimate..40....43.....48....53....60.....68....79....93.... .110...132....160


My estimate is based on the average of the following two formulas, both of which seem to be okay approximations just different line shapes:

1) 28.5341477 + (10 ^ ((9 + knob line) / 9.439247525))

2) 27.0456502 + (10.263297759 ^ ((10 + knob line) / 10))


If you plot these out in an Excel chart you will see that (assuming the printed Hz values are precise, which seems unlikely) my lines are both a bit low for the "known" values at line 3 and 6. It appears that much more complex formulas would be needed to raise those values while keeping values at line 1, 9, and 11 mostly unchanged. Obviously I tried to stay with whole numbers for the knob line section of the formula, but maybe tweak there or some sort of merging of the two formulas would make for an even better match.

Volume Knob


I also asked what wattage or percentage of output is represented by the volume knob lines. The response was again, don't know, can't really say. I'd like to figure this out too, but am not sure how to with out damaging the amp, my multi-meter (assuming that would even work in this application), or myself. If folks can tell me the safe and correct way to test the output of the amp, I may very well try to figure it out and post - or perhaps someone with more knowledge and/or experience could run with it.
 
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