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DIY Stompboxes => Building your own stompbox => Topic started by: azrael on December 15, 2009, 10:11:22 PM

Title: Ampeg Scrambler - Which layout is right?
Post by: azrael on December 15, 2009, 10:11:22 PM
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?
Title: Re: Ampeg Scrambler - Which layout is right?
Post by: PRR on December 15, 2009, 10:49:30 PM
Read the PDF on the TonePad site:

(http://i50.tinypic.com/a37l4.jpg)
Title: Re: Ampeg Scrambler - Which layout is right?
Post by: azrael on December 16, 2009, 03:24:04 AM
Oh, thanks for clearing that up. Missed that detail. I used the uStomp layout, so I was a bit worried haha.
Title: Re: Ampeg Scrambler - Which layout is right?
Post by: Jarno on December 16, 2009, 04:08:58 AM
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).
Title: Re: Ampeg Scrambler - Which layout is right?
Post by: MikeH on December 16, 2009, 04:46:45 PM
Honestly it doesn't sound that different with the extra diodes.  Sounds like doom either way.
Title: Re: Ampeg Scrambler - Which layout is right?
Post by: PRR on December 19, 2009, 06:50:49 PM
> 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.