Howdy everyone,
My soldering iron stayed cold during covid, but I'm now back to tinkering around. Putting my preamp and EQ onto a PCB has been a tall drink of water for me.
You'll notice the signal starts on the left and follows a U shape counterclockwise. I'm worried that this looks too sloppy.
Two questions:
1. How does this look so far? (From a general bird's eye view.)
2. Should I abandon this approach for a full ground plane, a few ground pours, and/or more than two layers?
Thanks in advance!
Dan: I'm just a "beginner" in the area of PCB design (see attached PDF file), but I think I can offer you some assistance.
- TOPSIDE ROUTES = RED
- BOTTOMSIDE ROUTES = BLUE
- TOPSIDE SILKSCREEN = WHITE
- BOTTOMSIDE SILKSCREEN = CYAN
- TOPSIDE SOLDERMASK = BRIGHT (or, LIGHT) GREEN
- BOTTOMSIDE SOLDERMASK = DARK GREEN
- It looks as though the drill holes for your tubes are slots. If they are, that's gonna cost you plenty!!!
- Your routing has several "acute angles", which are known as "acid traps" and those will cause your routes to loosen off of the PCB.
- It looks as though the spacing between two routes is too small in places (what is the routing DRC setting)?
- In what looks to be "C3" (small part up by "Audio In"), the two pads look to be shorted together by a RED trace. Is that supposed to be like that?
I am assuming that your PCB program is either EAGLE or KiCAD since those are the dominant FREE programs that everyone is using these days. If so, send me your actual CAD PCB layout file, as my PCB design program can import both of those files. Then, I will be able to take a better look at your layout and also be able to offer you some better suggestions.
While 4-layer boards are more expensive than your run-of-the-mill 2-layer boards, these days the cost difference isn't as much as it used to be. I have been thinking of re-designing a vacuum-tube radio transmitter and putting its filament DC voltage on the inner-layers like how you had mentioned. In thinking about it further, it may possibly even require a 6-layer board: L1 - TOPSIDE ROUTES, L2 - GND PLANE SHIELD, L3 - Filament-1, L4 - Filament-2, L5 - GND PLANE SHIELD, L6 - BOTTOMSIDE ROUTES. So, as you can see, the two GND PLANE SHIELD layers surround the two FILAMENT layers and act as a shield for the two outer routing layers. Just a thought.
What you are calling "Ground Pours" is commonly referred to as "Copper Pours" and in general, they are always a good thing.
> BUT!!! < there is more to it than just flooding an area with copper!!! 1) The "Copper Pour" has to be connected to GND, 2) The "Copper Pours" on both sides of the board need to be connected to one another!!! YIKES!!! How do you do
THAT??? Well.....doing that requires a boatload of what are called "stitching vias". What are "stitching vias"? "Stitching Vias" are independent vias that are connected to GND (or, whatever NET NAME your "Copper Pours" are connected to) and they need to be placed in such a manner as to connect a TOPSIDE COPPER POUR and a BOTTOMSIDE COPPER POUR together.
And, by my using the term "boatload", I mean "TONS" of them!!! You need to think of each via as being a teeny-tiny resistor and by having lots and lots of vias placed within a "COPPER POUR", which is effectively the same thing as having gobs of resistors in parallel. And, what happens when you have resistors in parallel? The overall resistance is reduced. So....."The More The Merrier" when it comes to "Stitching Vias" that are placed within "Copper Pours". And, since the "Stitching Vias" are only vias within a "COPPER POUR", the drill size and via pad can be much smaller than a component pad. You could use a drill size of 10-mil with a 14-mil pad (which will give you a 2-mil annular ring) because the via is embedded within a "COPPER POUR".
In any case.....I could give you a much better assessment if I had your actual PCB layout file. I tried enlarging your image file and after a bit, it just became too fuzzy to easily read anything. Your call.....
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