http://generalguitargadgets.com/diagrams/dist_250_lo.gif

Im wanting to add a spst switch to switch between the standard silicon diode pair to a pair of germanium or ect.. on my Dod 250. I made a little board that has 2 diodes like the pic and placed a wire from just before D2 to switch and the new diode pair board and the other going to the switch and ground. Im sure i did this wrong. Any ideas on how to do this right ? This is the same thing thats done on the pic at the ggg site that i want.

looking at the schematic - i was wondering if i place the switch just after r9 (10k) and right after c7 .001 output cap?
http://generalguitargadgets.com/diagrams/dist_250_sc.gif

If you want to switch between two diode pairs, etc., you'll need a spdt and the easiest way to wire them would be like this:

It can be done with a spst. Use the switch to shunt the diodes with the lower voltage drop across the ones with the higher drop (i.e. use the switch to put the diodes with the lower drop in parallel with the other diodes). When the switch is open the diodes with the higher drop will be active. With the switch closed the diodes with the lower drop become active.

Very cool! thats what i was looking for!!! Thanks all!

WHat im trying to figure out now is - where does the middle lug on the spdt switch? I can see the diode pairs both connect to ground. ( btw- im using half of a dpdt switch- I assume thatll be fine)  This is using the diagram  from above.

The middle lug of the spdt should go to your output signal between r9 and c7 (where your diodes would be connected normally).

If you're using an etched board, you will have to alter the layout a bit.  Or, you can use one of the diode pads (on the r9 side--right where the d1 and d2 labels are) to connect to your switch, then actually put your diode pairs on the switch itself.  It's not very tidy, but it works.

Someone correct me if I'm wrong, please.

Ill give that a try - thanks.