EHX Attack EQ question

[gigimarga]

Hello,

Bored of EQs, I've just finished an EHX Attack EQ using this schematic: http://www.diystompboxes.com/smfforum/index.php?topic=62459.0 (many thanks to Henry Jackobsen!)
It worked from the first try, but the "High" pot seems to affect the sound only a little, at the maximum (in opposite with the "Low" pot which has a huge effect on the sound).
I've tested it on a Squire bass, too.
In the manual (http://www.ehx.com/assets/instructions/knockout.pdf) is written that the low-pass filter has a 85Hz cuttoff frequency, and the high pass filter has a 6500Hz one.

Is the frequency of the high filter inappropiate or I made a mistake?

Thx a lot all!

[gigimarga]

I replaced the "High" pot and now it works OK on guitar.
But on bass the "High" pot is very subtle, so I think that the corner frequency of the filter is the problem (6.5kHz).
How can I modify it (to lower his corner frequency) to be more effective on bass?

[gigimarga]

 

[Fender3D]

Increasing C11, C12, C13 and C15, C16, C17 you'll obtain a lower filter's fc.
Keep them on the same ratio though (C11=10C12=100C13).
Doubling their values you'll half the fc.

[gigimarga]

Increasing C11, C12, C13 and C15, C16, C17 you'll obtain a lower filter's fc.
Keep them on the same ratio though (C11=10C12=100C13).
Doubling their values you'll half the fc.

Thx a lot Fender3D!
It's enough simple to do that, because I will double each cap on the copper side of the PCB  ...so I will have the fc around 3.25kHz.

Anyway, which is an appropiate corner frequency for highs on a bass?

[Fender3D]

With bass you're 1 octave below guitar, ie my A is 110Hz your A is 55Hz.
Halving the fc should be ok.
Remember you're dealing with an eq, then its a matter of try and listen too
A simple simulation with LTSpice will help to understand what's going on.

[gigimarga]

Thx again Fender3D!

The simplest simulation in LTSpice it's very complicated to me because I nerver used right now

[Fender3D]

Right click > save as www.wizardinside.it/foto/EHAttackEQ.asc

When in LTSpice:
Run > left click on "High" and "Low"
You should see the freq. response drawn.

Click on resistors and/or capacitors to change their value, then run, and you'll see the freq response updated with the new value(s)

[gigimarga]

Right click > save as www.wizardinside.it/foto/EHAttackEQ.asc

When in LTSpice:
Run > left click on "High" and "Low"
You should see the freq. response drawn.

Click on resistors and/or capacitors to change their value, then run, and you'll see the freq response updated with the new value(s)

Wooow...thx a lot man...it's very interresting this LTSpice!
I think I find a new method to lost my nights for a couple of days
Anyway, on the frequency response I have 2 plots: one with a dotted line and one with a continuous line? What are them for?

[Fender3D]

the dotted line is the phase response
the continuous is the frequency response

[gigimarga]

Thx Fender3D!

[gigimarga]

Increasing C11, C12, C13 and C15, C16, C17 you'll obtain a lower filter's fc.
Keep them on the same ratio though (C11=10C12=100C13).
Doubling their values you'll half the fc.

I doubled the values of the caps above mentioned and it sounds better now on guitar (more useable high pot).
Still not tested on bass...