Boss GE-7 - Frequency Change

[Dirty_Boogie]

Hi folks,

I'd like to change the frequency of the 800Hz slider on an old Boss GE-7 to 750Hz (my favorite slider on the Mesa-Boogie EQ). Since the 10K slider can't change, can anyone provide me with exact value changes I'd need - assuming one or more of C5, C6, R6 and R7 will need to change. And since I'd like to see how this is calculated, feel free to point me to a link on how to do this.

Boss GE-7 Equalizer guitar pedal schematic diagram

Schematic diagram of the GE-7 seven band graphic equalizer from Boss. Each of the 7 controls adjusts a slightly expanded octave to yield 15dB cut or boost. The level control helps to set the balance between normal and effect sound.

www.hobby-hour.com

Thanks!

 

[Cybercow]

Taking a stab at the cap values, (the resistors should be fine as they are), C5 would likely be upped to 180nF (from 150nF) and C6 upped to 10nF (from 8n2). I did not use any formula or math other, other than some mental interpolation based on the skew/change of 50 Hz from 800 Hz to 750 Hz and the nearest neighbor of the respective cap values.

 

[Cybercow]

Actually, after pushing my value changes thru the Gyrator Filter Calculator, the result comes to about 653Hz with a Q of 4.1

If C5 is left alone (at 150nF), just change C6 to my suggested 10nF value. In the Gyrator Filter Calculator, that result comes to about 715Hz with a Q of 4.49

If want to nail 750Hz, only change C6 and R6. Change C6 from 8n2 to 10nF and change R6 from 330R to 300R. In the Gyrator Filter Calculator, that result comes to about 750Hz with a Q of 4.71