Ampeg Scrambler - Which layout is right?

[azrael]

Why are there two diodes on this layout:
http://ustomp.com/?p=9
and five on this one:
http://www.tonepad.com/getFileInfo.asp?id=31

Which is the correct Scrambler?

[PRR]

Read the PDF on the TonePad site:

[azrael]

Oh, thanks for clearing that up. Missed that detail. I used the uStomp layout, so I was a bit worried haha.

[Jarno]

I put in all diodes, and it's wonderful, a very nice octave up. Didn't have any darlingtons, so I piggybacked BC560's. There's also a layout somewhere, which is meant to be used with 560's (two sets of holes in the place of each darlington). But I used the tonepad layout, and it worked on first startup (just some biasing issues, which is to be expected when subbing transistors).

[MikeH]

Honestly it doesn't sound that different with the extra diodes.  Sounds like doom either way.

[PRR]

> it doesn't sound that different with the extra diodes.

I can't see why either one is necessary. I wonder if they were left-over from a previous idea, or were over-cautious design. The pair should never do anything, the single looks like unnecessary protection. Like the breadboard was copied to a PCB, then in final testing it was realized that the diodes were probably doing nothing, a waste of 6 cents. In mass production, 6 cents matters. Easy enough to tell the workers to omit them, not worth burning a new PCB mask until the first mask wears out. Since this thing seems to be rare, they probably never wore-out the PCB mask.