Ge-7 and other graphic EQ mods.

[YouAre]

This isn't one of those threads that asks "what are some good mods for the ge-7..." so don't worry 

I want to know how to adjust the caps and resistors to get the frequencies i want, and the equation used to get them.

Here's the schem: http://www.mif.pg.gda.pl/homepages/tom/files/bossge7.pdf



Also, has anyone built the parametric or graphic EQ's on the geofex site? http://www.geofex.com/Article_Folders/EQs/paramet.htm

Can anyone compare the two?

Thanks for the help!

[YouAre]

Gentle bump. I know one of you out there has some experience with this! Come on, admit it! How many of you are lurking and subscribed to this thread?

[earthtonesaudio]

I have a GE-7 and I breadboarded one band of the GEOFEX parametric once long ago.
Not really much to compare, the Boss is a bit noisy compared to the GEO, but it has all the extra buffers/FET switching and an extra gain stage, so that's not much of a surprise.

The GEOFEX article you linked to has the info you seek about tweaking the gyrators to different frequencies.  But it also says in there that altering one variable will affect the others.  So you can't change frequency without also changing gain and Q.

But just to give you an example: for the first gyrator, make R16 and/or C10 smaller and the frequency goes up.