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Dirtbag R48 and C33 order.

Started by JakeFuzz, November 19, 2012, 12:31:04 AM

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JakeFuzz

So I was looking over the DBD schematic a few weeks back and thought I would compare it with some of the schematics that were out there. There are tons of random schematics out there, many of which say different things but for the most part the most reliable agree with the DB schem. I came across someone who posted some help pics in a fixer thread about a DMM and noticed just tracing by eye that the order of R48 and C33 are reversed from what the DB schem says. I modeled the frequency response in simulink and the responses from both arrangements  look identical but I figured it would be an easy 5 min swap sort of deal to just give it a try. I just did it and I think it sounds a little brighter (on the repeats) and more like some of the DMM demos I have heard on the tube.

Has anyone looked into this? I've found a few schematics that show the cap/res combo both ways. The change is pretty subtle so I am not sure how much it actually changed and I don't want to crack it open again and switch back.

madbean

I have not seen it arranged that way...at least not in the factory schematics I referenced. I don't know why there would be a difference....perhaps it relates to the impedance of the 470n?

Alternatively, if you are after brighter repeats reducing that 47n to ground should do it.

JakeFuzz

Yeah almost every schematic I have seen shows the same arrangement. There is one that shows it the other way around which was what had me looking at that area to begin with. I believe it is this one:

http://rkerkhof.ruhosting.nl/Posts/MM5.JPG

Then I found these high rez pictures of the original PCB where you can see that they are arranged like that.

http://www.diystompboxes.com/smfforum/index.php?topic=76178.0

I just though this was interesting and thought it would be fun to see what (if any) change it made. Still loving the circuit and wanting another one!