Need help with tone stack

[marcoloco961]

I'm trying to use a FMV tone stack on a Bass Amp build. The stack itself is heavy on bass to begin with, but I would like to keep this style of stack for now before venturing into some of the other available designs.

My problem is with one simple equation. I am trying to determine the value of the mid pot. In order to figure this I need to know the value of "B" or attenuation. In Merlin's book it states B = 10 -10dB/20. The -10dB/20 is in the exponent position as if to indicate to the 3rd power, etc. He gives the answer to the equation as .32 for the -10db targeted. To save myself I cannot come up with .32 no matter how I try to perform the math. I know I am just not understanding the way the equation is written and would just use the .32, but I would like to shoot more for about the -15dB Range instead of the -10dB, so I really need to understand the math (Duh). I can't seem to find the answer anywhere in all the sites I have looked at up until now, or in the book anywhere.

Would someone care to enlighten me as to what I am missing here?

[Bob-I]

Go here http://duncanamps.com/software.html and download the tone stack calculator. You'll be able to plug in the values and see the results.

[martin manning]

TSC is a good way to go. Here's the math, though: If the attenuation is 0.32, as in Vout/Vin = 0.32, then in dB's that is 20*log(0.32) = -9.9 (pretty close to -10). If you want -15 dB, then you need attenuation B where 20*log(B) = -15, or B = 10^(-15/20) = 0.178

[marcoloco961]

TSC is a good way to go. Here's the math, though: If the attenuation is 0.32, as in Vout/Vin = 0.32, then in dB's that is 20*log(0.32) = -9.9 (pretty close to -10). If you want -15 dB, then you need attenuation B where 20*log(B) = -15, or B = 10^(-15/20) = 0.178

Thanks Martin, I am that far, I guess what I am trying to say is I don't understand what the "^" means. (i.e. (-15/20) = -0.75 ) If I were to use my calculator Pushing the buttons 20*log* .32 I get the answer 8.326.... If I go 20 log*.32, I get .416....no where near -9.9... I am feeling ultra stupid right now, it has been a long time since math classes. Expand on the "log, ^" part please, or just tell me how to punch it in on a scientific calculator.

Why is it, the more I read and learn, the dumber I feel??

[statorvane]

Expand on the "log, ^" part please, or just tell me how to punch it in on a scientific calculator.

The "^" means the following number is an exponent. That is, in the example 10 raised to the -0.75 power, or the anti-log of -0.75. It is the functional inverse of the log (log base 10).

[Ian444]

If I were to use my calculator Pushing the buttons 20*log* .32 I get the answer 8.326

It's the order in which you push the buttons. Try entering 0.32 then log then x 20 and you will get -9.9 you are confusing your calculator, which isn't difficult Just to put the meaning of ^ in some old school words, it can be translated to this: "^" means "to the power of".

[marcoloco961]

Thanks guys. I was getting frustrated. I made it through Algebra, Trig and Calc, back in the day. Too bad the day was decades ago. I couldn't remember to save myself. Thanks again.

[Structo]

Order of operation.

My Dear Aunt Sally

Multiplication, Division, Addition and Subtraction

[ChrisM]

BEDMAS

Brackets Exponents Division Multiplication Addition Subtraction