King of Klones and question(s) about diodes

[GhostofJohnToad]

So I have started to solder together my first project, the King of Klones. I am trying to understand some things about diodes.  Here's the background data for this particular build:

Here's what's spec'd out:
D1 - D4 = MA856
D5 - D6 = 1S1588
D7        = 1N5817

Here's what I planned on using:
D1 - D4 = 1N914
D5 - D6 = 1N4001
D7        = 1N4001

I believe the DIP2 switch will allow me to switch between the 2 banks of diodes. (D1-D4) and (D5-D6).  Is this correct?  If these are in fact separate banks. What does D7 do?

Given this variation with the switch should it be necessary to socket all the diodes to provide further variation?  How much will the diodes change the overall sound of this pedal?

Any help appreciated.

[Haberdasher]

d7 = polarity protection. it would prevent certain components in your circuit from cooking if someone ever plugged a "center pin positive" power adapter into it.

[GhostofJohnToad]

d7 = polarity protection. it would prevent certain components in your circuit from cooking if someone ever plugged a "center pin positive" power adapter into it.

Thanks, that eliminates a reason to socket that one.

Knowing that helps me to understand the schematic a bit better as well.

[bigmufffuzzwizz]

I'm planning on making the same diode changes as you are but in my Aristocrat. The originals diodes used are way too expensive.