modifying distortion circuit

Pauld35

Member
2014-09-27 11:16 am
hi,


have modified some parts of a distortion circuit and have a few questions, about weather a part of the circuit is now obsolete.....
and also where some dynamics/headroom may have been lost with the modifications and if they can be re-gained some how. (still have no O.scope sorry)


the sound is very satisfactory except for sounding more compression. the three main alterations are,


(A) D3 & D4 from 1n4148 to 1n4001


(B) R1 from 470r to 1K (reduce gain)


(C) remove C28 10nf (no jumper/ open circuit )


some coupling values have also been changed and C6 27n is now a 5way selector switch ranging from 15n to 100n.


please see the circled high lighted schematic for the main changes.



wondering R25 & Q5 may be obsolete now?
maybe D3 D4 is responsible for too much compression?

any advice on how to re gain some dynamics would be appreciated.


cheers
 

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By definition distortion circuits reduce dynamics, that´s their job.
If you want more dynamics switch distortion OFF.
(A) D3 & D4 from 1n4148 to 1n4001
No change expected.
(B) R1 from 470r to 1K (reduce gain)
Not needed.
If you want less gain, simply lower RV1 (distortion) setting 1 notch or 2, that´s its job.
(C) remove C28 10nf (no jumper/ open circuit )
Why would you do that
It´s part of a gyrator circuit which equalizes the pedal sound, by removing C28 you now lobotomized it.
and C26 27n is now a 5way selector switch ranging from 15n to 100n.
C26 is shown as 220n ¿¿¿???
IF you meant C6 , it would change gyrator boost frequency, but since you lobotomized it ......
wondering R25 & Q5 may be obsolete now?
R25 is U1b bias reference, pulling it would be similar to smashing your hand with a hammer and then trying to play.
Q5 function has effectively been destroyed by removing C28.
maybe D3 D4 is responsible for too much compression?
I hope so, that´s their job.

I think you are barking at the wrong tree here, just enjoy your distortion pedal as is, it has been designed by very qualified Engineers, and if you want to Mod it for good, study a lot until you reach their level.

Now if the goal is to Mod it for bad, just keep pulling parts at random.

It reminds me of the Hal scene at 2001 Space Oddissey when HAL brain parts were being pulled one by one.

YouTube

I bet if your pedal could talk it would tell you: "please stop Paul, I´m afraid".
 
By switching in the 1A doses in place of 150mA ones, you may have lost little headroom. If you'd accomplish the same with 7 of the original diodes in parallel to get the same 1A rating, for a given low current, the voltage drop would be less.

You could use pairs of diodes in series to increase the voltage before clipping starts. Or put a resistor in series with them to soften the clipping.