Joe Davisson's Vulcan preamp

[joecool85]

For those looking for the link to the schematic: https://www.diystompboxes.com/analogalchemy/sch/vulcan.html

I'm curious what the diodes are for between the stages though.  Not sure I've seen that before.

[Miyagi_83]

Hi, joecool85.
Sorry about not posting the schematic or link. I should have done it in my first post. My bad.
Actually, it's this one
https://www.diystompboxes.com/analogalchemy/sch/v4preamp.html
The one you provided shows the 3-stage bjt Vulcan overdrive pedal and they sound completely different.
As for the diodes, I used 1N4148.

[Miyagi_83]

Update

So, I have been tweaking the circuit for the past couple of days and I think I've got it where I like it. Actually, there are a few versions that I'm fond of, so I'm going to make it a switchable two or three-channel preamp. Honestly, this design has enormous potential, afaic. I haven't tried it on 18V yet. That's still on my to-do list.
Now I'm going to need a nice clean channel to pair with it. Any suggestions are welcome.

Is it OK to post a schematic with my changes? On his site, Joe Davisson put the 'do not copy / all rights reserved' clause, so I wouldn't like to infringe his copyrights, annoy him or anything like that, hence my question.

[edvard]

For those looking for the link to the schematic: https://www.diystompboxes.com/analogalchemy/sch/vulcan.html

I'm curious what the diodes are for between the stages though.  Not sure I've seen that before.

Per the description below the schematic; "The diodes in the bias network prevent hard-saturation of the transistors."

I won't pretend I'm smart enough to know how that works, but it sounds to be in the same vein of putting a diode across base & emitter to prevent zener breakdown events that degrade the junction and cause noise to build up over time.
See here: https://www.diystompboxes.com/smfforum/index.php?topic=132039.0

I wonder if those two arrangements might be considered general good practices for BJT-based preamp circuits?