Turn your input buffer (OPAMP) into a (frequency adjustable) boost for 3$

[thomasbe86]

I have been adding this additional control for IC input buffers builds; Deviations of the Ibanez ST9 stage called mid boost, you get a nice frequency adjustable boost to get clipped into further stages, quite nice.
Here is the AC Sweep right after the stage (measured between C3 and R4):
you can see the magnitude going down the higher the frequencies , this allows for an even perceivable boost across the range of the knob.


The original buffer:



The modified buffer:


With details on the DPDT switch:


What my board looks like (2.5cm*2.5cm) (you can use a jumper between R6 and DPDT1 pin 4 if you have only one copper layer on your board):
(note that C4 lead spacing is 2.5mm and C5 is 5mm)

The bill of material:


Gerber and other files are available here:
BFRTRSNCBST Project Folder

Hope you enjoy this!
Thanks,
Thomas

 

[t1redhands]

Excellent stuff! I'm going to put one of these into a guitar. Thanks!

 

[thomasbe86]

Watch out, the board is only to add to an existing buffer (connecting IC pin 1 and 2 as well as the ground).
you'd need to add the whole buffer circuit (4 capacitors, 8 resistors, 1 potentiometer, 1 dpdt switch and 1 8dip IC) into your guitar, including the power supply (+9v for VA and a voltage divider for VB, potentially a protection diode and RC high pass filter to avoid hum, 3 capacitors, 3 resistors, 1 schottky diode, and the 9v battery), that's 22 components total on top of the 9v battery
It gets quite bulky for adding into a guitar.

 

[Silver Blues]

Cool idea! Definitely gonna add this to my list of circuit snippets and play with it in some bigger circuits.