Please help me with my Guitar Preamp design

[Vivek]

Some random thoughts about the project I am trying to do


It will be more like a Preamp rather than a Distortion Box (Multistage distortion and great EQ puts it into Preamp category rather than Distortion Pedal). But it wont try to emulate the gain/EQ of any existent Preamp.


It will be more like a workbench  (either you build it and only tweak the front panel knobs) or it has extra PCB place and holes  / sensible points to experiment with lots of mods.


Users can decide which controls to bring to front panel and which to keep as trim pots on the PCB.

It will go from Clean buffer to hard rock but will not be really designed for Metal, Swedish, Chainsaw (Though it will be possible to mod it easily for those genres)

It will not be based on Opamp saturation. I will try to rely on Diode saturation which I understand is cleaner and more predictable. There will be a cost to this since it will need more stages / more PCB place to get the desired final gain.

It will have high Vcc since the idea is to even have it used as a clean buffer with EQ and to avoid IC rail saturation at each stage.

It will have some paths to mix clean signal with distorted signal in different ratios, at different points.

It will have 2 or maybe 3 stages of distortion. It will have some EQ filters in between the sections

It will have some control of EQ before distortion. I am now thinking of 2 Mid Boost/cut knobs (maybe like +/- 12 dB at 700 Hz and 2 Khz) which vary the gain but keep the frequency and Q fixed. This I hope will have great effect on final sound, from pre-distortion mid scoop to mid boost. Since these knobs will interact, there should be many interesting possibilities of shaping the pre-distortion mids.

There will be BMT and maybe P controls after the distortion stages. I dont feel like using a 3 knob Baxandall due to too much interaction of knobs and very low Q of Mid control. I might go for B and T on a Baxandall while Mid gets its own section

In effect, it might have 3 channels

-- Only input clean buffer -> EQ-> Out

-- input clean buffer -> 1st stage distortion -> EQ-> Out

It might have ability to mix in clean signal, but if first stage does low clipping, I dont know how useful that can be.


-- input clean buffer -> 1st stage distortion -> 2nd stage distortion - >  EQ-> Out
+ ability to mix in the clean signal


( The twin peak pre-distortion Mid section goes in at the right place in above chain)


The diodes will have compliance resistors, to be able to go from clean to slight warmth to transparent overdrive to slightly harder distortion.

I would value the comments of this lovely forum, to help me design the Preamp.

[11-90-an]

This seems to be good...
https://www.diystompboxes.com/smfforum/index.php?topic=125355.0

More on for OD and distortion, but can have nice clean tones also. @jonny.reckless, the creator, said that a cabsim will probably be needed.