I'm currently building this distortion circuit for a guitar pedal.
I didn't have any 2N5089 transistors so I decided to try using 2N3904s instead. The result has been an extremely harshly clipping output, due to the higher gain characteristics of the 2N3904. In order to tame this harshness, I would like to try and insert a low pass filter before the last stage of amplification/distortion.
So the Blackfire runs essentially:
buffer -> amplifier -> buffer -> dual amplifier -> output
And I would like it to run:
buffer -> amplifier -> buffer -> FILTER -> dual-amplifier -> output
The the stage of the Blackfire that I would like to filter into is based on a canonical multi-stage transistor amplifier circuit, but with the output of the preceding buffer biasing the input of the following transistor such that C1 and the R1-2 voltage divider aren't necessary:
My intuition was to put C1 and the R1-2 junction back in and then add a second capacitor such that C1 would become C1a and C1b. My thinking is that this should further decouple the segment between C1a and C1b, into which I should be able to insert the filter.
However, this has only resulted in a significant loss of signal strength, and no desirable filtering effect to speak of.
I've searched through my archive of guitar pedal schematics and various DIY pedal sites, and haven't been able to find any examples similar to what I'm trying to do. Which leads me to a few questions:
Is what I'm attempting feasible/possible?
If it is, should the filter be active or passive?
How should I go about implementing the filter?
Could someone explain why the filter I've tried to insert hasn't worked?
Thanks much in advance!