What does it do? Well it does clean boost with the Gain set at minimum, flick on the Dirt switch and you get some nice diode clipping too. Turn up the Gain and you'e into overdrive territory with diode clipping, flick the Dirt switch off and you get even more overdrive. All with some nice tonal variations courtesy of the tonestack, typical Big Muff Pie Tonestack. You can easily tweak the tonestack to taste.
You can also try different diodes for D5-D6, keep in mind when they are engaged you will loose some output, but there should be more then enough output with them engaged. What may be a nice tweak is to change the Dirt switch to a pot so you can control how much of the signal gets clipped by the diodes.
I opted to have the power on a separate board to help avoid issues with interference with the rest of the circuit. Make sure you are rated at least 50V due to the increased voltage from the doubling at the powerboard, which gives out approximately +35V. Also, on the power board you'll notice that I have 2 connections for the heater pins of the tubes, pins 3 & 6, but you can just run 1 wire to tube 1 then have a wire connects to the pins of tube 2.