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Building an Equalizer (Frequencies and Circuits)

#22
Sir Edward V said:
Now I can't figure out how that guy is determining what capacitors to use to get what frequencies.

HELP!!! :help:
Click to expand...


Don't know if you got this part, but it looks to me like you just calculate the maximum L and minimum L of the simulated inductor there by L(eff)=R1*R2*C2... R1 is the 470 ohm resistor in the diagram, R2 is the min/max values on the frequency pot, and C2 is C2 in the diagram... Then use the two L's you have in Fq=1/(2*pi*L*C) to get the min and max frequency for that band... it ends up being a bit of math but excel would let you check things pretty quick, and R.G. has values in there for 2 mid bands that are close to a decent range for bass mids. (IMO)...

I guess to get cap values, I'd work backwards from frequency, probly with an excel sheet and trial and error as we have some ballpark values that work. There's probably a more elegant way to do it, but this is easy, relatively fast and doesn't mean I need to go and review any math since its been a few years. Maybe steal the C1 and L values from a graphic EQ schematic and work into the equations given from there...
 
#23
jucas said:
Don't know if you got this part, but it looks to me like you just calculate the maximum L and minimum L of the simulated inductor there by L(eff)=R1*R2*C2... R1 is the 470 ohm resistor in the diagram, R2 is the min/max values on the frequency pot, and C2 is C2 in the diagram... Then use the two L's you have in Fq=1/(2*pi*L*C) to get the min and max frequency for that band... it ends up being a bit of math but excel would let you check things pretty quick, and R.G. has values in there for 2 mid bands that are close to a decent range for bass mids. (IMO)...

I guess to get cap values, I'd work backwards from frequency, probly with an excel sheet and trial and error as we have some ballpark values that work. There's probably a more elegant way to do it, but this is easy, relatively fast and doesn't mean I need to go and review any math since its been a few years. Maybe steal the C1 and L values from a graphic EQ schematic and work into the equations given from there...
Click to expand...

I tried it for like half an hour, I couldn't get the values he got from those capacitors and those equations...

why don't you try it out for me :D see if you can actually get the values from what he supplies
 
#25
Sir Edward V said:
I tried it for like half an hour, I couldn't get the values he got from those capacitors and those equations...

why don't you try it out for me :D see if you can actually get the values from what he supplies
Click to expand...

Actually tried it out as I had a lull at work, and you seem to be correct. I played with the units for a while and can't really get things to work out... so, I'll probly try again later since I was a little rushed and its bothering me that it isn't working out right now. Its probly going to be some stupid thing we both overlooked and I'm going to feel stupid when we get it.

Edit... Just looked at the graphic EQ bit and there's a missing square root in his parametric section on the frequency calculation... I'm going to put it in and see if it works out, but that's probly the issue.

, here's a sheet with some close values... like 131-584 Hz and 483-2100Hz. Couple blanks to try cap values and should give you frequencies in the end. Let me know if it doesn't work. View attachment EQ.xls
 
#26
I know you want to build it yourself but this could give you ideas.
G-Drive-large.jpg
 
#28
So I have spent some time cross referencing that web site to a couple others I found through Wikipedia, and I still can't figure out what that guy did... So either there is something I am completely missing or misunderstanding, or that guy pulled those values out of his a**!! :mad:

:help: :help: :help: :help: :help: :help: :help:
 
#29
So I think that guy did mess up the numbers somewhere... or something...

But I found this other site that also explains things, and his numbers are justified, so I think I will be using his schematic for inductors and finding cap values that work to get the frequencies I want. So I will use his schem. for the inductors and use that other site for the general EQ schem.

so I'll probably draw up my own schematic using those, I'll post it when I get it done!

Hopefully all this bisnatch works!
 
#32
Sean S said:
so what have you decided to build yet? I would personally build a semi-parametric EQ, with set bass & treble frequencies (shelving?), and selectable mid frequency, Q, and level. Or, perhaps, separate the mids (low & high)
Click to expand...

Yeah I was going to go with 4 bands, and I thought about the high and low shelving as well, but I don't know how to do that yet... I will probably look into it soon... but I think if I did shelving I would try to do adjustable frequency for them

but yes, the mids will have adjustable Q, freq, and level... I may or may not put one in front of the LBM as well... thats a lot of knobs... at least like 24 knobs :eek: maybe I will look into getting some of those fancy two-layer knobs that would save lots of space
 
#33
Sir Edward V said:
So I have spent some time cross referencing that web site to a couple others I found through Wikipedia, and I still can't figure out what that guy did... So either there is something I am completely missing or misunderstanding, or that guy pulled those values out of his a**!! :mad:

:help: :help: :help: :help: :help: :help: :help:
Click to expand...

Read the edits on my last post. He just forgot a square root in the parametric bits... theres a spreadsheet there where we get close to his numbers and you can fill in your own cap values to see what happens.
 
#35
Sean S said:
so what have you decided to build yet? I would personally build a semi-parametric EQ, with set bass & treble frequencies (shelving?), and selectable mid frequency, Q, and level. Or, perhaps, separate the mids (low & high)
Click to expand...

could you direct me to a site that explains how to make a shelving filter? I've done some searching and haven't come up with anything yet...

that is if you know where to find something like that :D :D

could I make a low shelf filter by making a low pass filter parallel to the other filters then adjusting it's level??
 
#37
Sean S said:
sorry, sev, I only have the first clue: google. other than that, i haven't the foggiest :hmm:

anyway, i was thinking, why not have switchable EQ/[fuzz/od/dist] bypasses? if for some reason you want to use just the EQ, or just one EQ with drive...just a thought.
Click to expand...

haha I've thought about that as well. I think I'm just going to keep it as fuzz only (no OD or distortion built-in), but I might just put in some switches (non-foot) to turn off the EQ(s) and the fuzz.
 

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