If you want it exactly like the original, you can omit the charge pump and associated components and take 9V directly to where VSw 3 connects to the board. Then use a 4PDT toggle instead of two SPDT and one DPDT for switches 1 to 3.
Info about Catalinbread's original:
Introducing the new Dirty Little Secret from Catalinbread. The Dirty Little Secret has earned itself a well-deserved reputation for replicating the sound and feel of a classic era Marshall amplifier, supplying one of the most iconic guitar sounds in music. Able to clean up with a flick of your guitar's volume control, or go from mild crunch to full kerrang with your pick attack, the Dirty Little Secret has seen the inside of arenas and bedrooms alike, providing great overdriven sounds to clean backlines, low-wattage amps, and even direct applications. When the JFETs used as the base for the Dirty Little Secret were discontinued, and as our stock of them began to dwindle we knew we had to find ones still being manufactured. However, rather than simply re-voicing around these new JFETs, we decided to push the envelope and provide an amazingly robust feature-set, from ever evolving listening and circuit skills, and pure power of intention. This isn't just 'a' Marshall in a box, it's the most versatile and dynamic Marshall-style overdrive out there!
What's new in the Dirty Little Secret:
• The DLS now offers two distinct voicings, "Super Lead" and "Super Bass" switchable via an internal slider switch.
• Completely redesigned full three-knob treble-middle-bass tone control complement that reconfigures for each mode setting.
• We've also added an internal presence trimmer that allows you to fine-tune the presence of the pedal precisely to your guitar and amp combination.
• The gain range is much wider and even more responsive to pickup types, playing dynamics and instrument volume knob!
The "Super Lead" mode expands the range of the DLS MkII with more gain available and more control over your tone sculpting with the addition of the midrange control without losing any of the touch-sensitive dynamic qualities that made the MkII so great to play - in fact, those qualities have been enhanced. The gain range now goes from classic plexi all the way to modified JCM800 levels and can get even more raw and open than any previous DLS. This mode was voiced specifically to make humbucker-equipped guitars really rock with clean to scream all from the twist of your guitar's volume knob.
The "Super Bass" mode is a new voicing that gives you the tone and gain structure of a Marshall Super Bass (which is very similar to a JTM45 or JTM50/100). This mode was voiced to really hone in on that elusive in-between "not quite clean, not quite dirty" response that old tube amps were so good at getting. And it was specifically voiced to make fuzz pedals sound great (especially two-transistor based fuzzes like the fuzz face). Plug a Strat into a Fuzz Face into the new DLS in SB mode and you'll see what we mean!
Single voltage only version. This was requested but it only saved one row, so I don't think I'd omit it for a bit of extra versatility. But here it is if you just want to power it using a single supply. [smaller version added]
Video of Geiri's build: