Schematic v/s layout question - trying to understand-

[jimbob]

http://i40.photobucket.com/albums/e243/stumper1/Layouts/CapnCrunchBox.gif

If you were to use this schematic http://www.matsumin.net/diy/bunkai/MI_audio_dist/MI_audio_dist.jpg and replaced the 4.7k R9 with a 20 k pot (presence) – also removing R8 (10k) I would assume lug #3 of the volume would go to lug # 2 of the 20k presence and lug # 1 of the presence to go to C9 (.022) then ground. This now leaves lug #3 of the presence to go to lug #1 of the 10kc Tone pot.

Does this go according to the schematic presented? I think so. However, This layout looks a little different? Am I off some where?


According to the newest/updated schematic R8 and R9 is removed and C8 is changed to a .022uf from .039.

It looks as though the layout here is the old schematic with a presence 20k pot added but I still can figure out the wiring seems different from what I think the schematic shows.

Anyone?
Schematic v/s layout question - trying to understand-

[DougH]

All I can say is, welcome to the club.

I've had similar problems with "orphaned" layouts that get posted with no references to schematics. I'll find a schematic that is supposedly the same circuit but with a few differences. Then either a) the layout was drawn wrong or b)it's a different version of the circuit and the schematic for it is presumably floating around somewhere.

All you can do is take the layout and draw your own schematic from it, then verify whether it agrees with the schematic you found or not. Then the only thing that tells you is if it agrees with that particular schematic, not if it is "right", "wrong", will work, won't work, how it will sound etc, etc.

For that reason I find the proliferation of "layout galleries" to be completely useless for my purposes. I don't care about layouts to begin with. I can take a schematic of 90% of this simple stuff and perf it up in 15-30 minutes. If a layout is posted along with a schematic reference, you can verify yourself if it is valid or not, which components to change for mods, etc. If not- you are lost and completely at the whim of whoever drew the layout.

I suspect, like a good game of "telephone" or "gossip" that many of the layouts posted have some inconsistencies with the original schematics. That's just a natural tendency. But without the schematic reference, you will never know. So the overall result of layout posting with no schematic reference and inconsistencies is that misinformation spreads.

I'll get off my soapbox. I've mentioned this kind of thing before but it seems to fall on deaf ears...

[petemoore]

I'll get off my soapbox.
  I'll get on.
  You did a fine rant Doug, not much I can add.
  Schematics are a forgone necessity more often than I'd like.
  I"ll take an interest in a subject, then realize 'the book' has been folded and torn and I want to:
A. Not try to read the tedious, time consuming layouts which tend toward various innacuracies.
B. Chastize those responsible for posting the layout without schematic.
C. Have nothing more to do with 'how's it work' or 'where's the HP filter'...any other type questions.
D. Go get the dern schematic.
  I used to do "D" and "B", but lately have opted for A and C options.

[DougH]

Yeah, I don't answer debugging questions with just a layout as a reference any more. If you want my help with a problem, post a schematic. It takes too much of my time to interpret a layout. (Which is one of the reasons I don't do pcb or vero for one-offs for myself. PCB makes sense for complex builds and multiple copies, esp high-quality solder masked pcbs. Vero makes no sense to me whatsover in any circumstance. Hard to follow layout with little or no relation to the schematic, no space savings over perf. What's the advantage? There is none. No point to that at all AFAIC. Perf is the easiest most straightforward way of producing a simple one-off IMO.)