Lowering a few dbs of 500Hz and below

[nero1985]

Hi guys, im putting a few circuits together and i've noticed that i always a bit too much of 500hz a below, when i run the pedals into my computer i use a graphic eq and taking all frequencies from 500Hz and below about 3 or 4 dbs does the trick. I have alnico 2 pros on my les pauls and they are a bit darker than usual.

Whats the best way to do this? I have tried a RC high pass filter but it removes all frequencies below 500 i just want to lower a few dbs.

Thank you in advance!

[Quackzed]

the rc high pass filter will, like you said , remove everything below the corner frequency. to adjust 'how much' gets removed you can put a resistor in parallel with the cap. this lets SOME of the signal get past the high pass filter through the resistor, rather than having all of it get cut...
if you use 500k pots, i'd start with a parallel 2.2n cap and 150k resistor before the pot for whichever pickup you want to alter... see if that cuts not enough / too much and adjust it from there... bigger cap will move the corner freq lower, bigger resistor will cut more lows out...
fwiw, this kind of 'in guitar' filter can behave differently depending on what its driving/ what its plugged into ... cutting less or more lows depending on the input impedence of the pedal or amp its plugged into...

[nero1985]

I will give it a shot in the AM, thank you very much!!

[PRR]

> tried a RC high pass filter but

Two parts is not enough.

You need three parts.

Two to set a "lower" level.

One to set the transition to the less-lower level.

In the plan below, the 5K and 10K define a -3.5dB "lower" level.

The 50nFd "shorts out" the 5K for higher frequencies to give nearly full level.



(As Gil says) Everything interacts (including the source and load!!). Suggest you make a pile of red-stripe resistors and 10 22 47 100nFd capacitors, and swap until happy or tired.

[ashcat_lt]

(As Gil says) Everything interacts (including the source and load!!).

Yep, and if this is inside the guitar, the source is going to be a big inductor with a relatively large series resistance, those resistors will probably want to be at least 20-50 times bigger, with corresponding adjustment to the cap value.  Else, you'll probably end up with less bass and no treble.

[PRR]

> guitar, the source is going to be a big inductor

I read this part:

"when i run the pedals into my computer..."

My plan ass-umes it is not facing a guitar directly.

[ashcat_lt]

> guitar, the source is going to be a big inductor

I read this part:

"when i run the pedals into my computer..."

My plan ass-umes it is not facing a guitar directly.

Yeah, it was Quack that was talking about inside the guitar, but then you came and kind of drew what he was talking about. 

Kinda begs the question - if he already has a solution???  I guess he wants to plug it into something else and is afraid there might be too much bass for that, but won't that thing have a knob marked Bass? 

OTOH - is the real problem that there isn't enough treble coming out of the guitar?  Maybe lighter-wound pickups or even a shorter cable is the answer.

Or maybe just switch to the bridge pickup.

[Quackzed]

well, he mentioned his pickups being dark and that he wasn't trying to mod a particular pedal,   i guess i  ass-umed he was looking for a solution for the guitar itself...
either way, maybee a better (less variable) solution would  be a  buffer/ booster type thing with a little adjustable bass cut/treble boost...
that way you could control in/out impedences inside the buffer/booster, rather than getting different results depending on what you plug into. i've tried this kinda passive thing in one of my guitars, but took it out for those reasons... into one pedal it was too thin, into another pedal it was too bassy... it was very finicky about what i plugged into first...

also, like you said, maybee a shorter cable, or just adjusting pickup height or different pickups if the ones in it are too dark ...