Philosopher's Tone simpler dirt

[lars-musik]

Dear fellows,

after reading about the Pigtronix Philosopher's Tone Gold I thought this would be my all-in-one solution: it boosts, compresses and even overdrives. Now that I built it I must say, I am rather disappointed, especially the "GRIT" (=drive) section sound too harsh on the verge of unusable to my ears. It seems to me that that building block is overly complicated (at least for my electronic knowledge) but maybe you can help me understand what is going on.



I see that the signal is blended between an unclipped signal (U4.1) and the soft-clipped one (U4.2) via the "Grit"-pot. C13 and R20 form a high pass filter (?) that cuts at 2,8 Hz (deduced from the calculation on the ElectroSmash Tubescreamer page (fc=1/(2π*R*C)). D7 to D11 will do some clipping, as the gain of the opamp is set by R19 and R20 to about 33.

So far. Now my questions:

1. Do R15+R17 and C11 form another high pass filter?
2. What do D1-D6 do?
3. Would that work (better)?



I don't see the advantage in clipping full blast and then blending that signal with an unclipped one in contrast to just dialing in the clipping I want.

For reference, here's the complete schematic of the original cicuit:




Thanks a lot (again)!

Lars

[Scruffie]

As I see it, R15 & 17 forms a voltage divider to cut the input signal for U4.2 to keep it at the same level as U4.1 and also gives a reference to D1-6 to provide hard clipping at 1.8V for U4.1.

When you say harsh to you mean as in treble? If so you could always increase C4 or if you only find it harsh when turned up, C12. You could also add some series resistance for softer clipping to D7-11.