Don't worry about where or how I live, but for your information I have a house, rather big and not made from " poop and hay " as you might seen in our country ( even if I did , that wouldn't make me less of a person, or in some people's eyes, "not pointing fingers" it would !? . ) , yes there are people with less then 200$ to live, but who are you to judge them?.
Point was about LM3886, PCB, the fun to build it yourself. Yes I'm not going to trow away 200$ for a LM3886 amp to build, I have several amps, this was just to make one with LM3886 since I never heard this ic and wanted to build one.
- Also I didn't even say anything about the price to be high , or low. nor that I want to buy one or not.
Yes, of course higher quality - higher the price, and most of the time it's worth it. But for what I'm doing here, I don't want to wait for shipment either from China, Canada etc. I want to make it myself, try the chip, keep it if I like it, trow it in the bin if I don't, simple as that.
@tomchr This is what I did so far, inspired by your design https://neurochrome.com/pages/taming-the-lm3886-chip-amplifier
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If I make a plane ground, all GND's on it, will that happen ?. How did you separate signal grounds from power ground?.
No, it won’t happen but it will tend to minimize the effects because the ground is relatively low inductance. Best of both worlds is accomplished by using a ground plane for everything except the input/feedback/speaker ground, and treating THAT one as a signal - which it really is. Return IT to the ground plane at exactly ONE point. You might use several PTH’s, but one point.
IF you are planning a ground plane, consider a 4 layer board. At a cheap board house it’s not a crazy cost adder. It’s apparent from this and other threads you are a relative PCB newbie - good layouts come with a lot of practice and chip amp boards, especially multi channel ones, are NOT the easiest things to design properly. Self’s grounding rules always seem to conflict with one another. Even worse when doing a single supply amp where power ground IS one of the supply rails. I’d suggest saving your money on expensive board houses and run them as cheap as you can for a while. You’ll have a lot of do-overs. Thats fine. It’s what you’re supposed to do. When I was where you are cheap runs were not an option and I resorted to surplus 18x24 blanks (where the copper was crudded up too much for manufacturing, and could be had for a couple bucks), a sharpie marker, and ferric chloride from Radio Shack. IC footprints could be done with rub-on transfers, which even provided alignment holes for the drill. #60 bits could be had at ACE hardware. I still have material and still make stuff that way. Some of it always will.
Don’t try to design a board you’re going to send out for fab in one sitting. Leave it for at least a few days and come back.
IF you are planning a ground plane, consider a 4 layer board. At a cheap board house it’s not a crazy cost adder. It’s apparent from this and other threads you are a relative PCB newbie - good layouts come with a lot of practice and chip amp boards, especially multi channel ones, are NOT the easiest things to design properly. Self’s grounding rules always seem to conflict with one another. Even worse when doing a single supply amp where power ground IS one of the supply rails. I’d suggest saving your money on expensive board houses and run them as cheap as you can for a while. You’ll have a lot of do-overs. Thats fine. It’s what you’re supposed to do. When I was where you are cheap runs were not an option and I resorted to surplus 18x24 blanks (where the copper was crudded up too much for manufacturing, and could be had for a couple bucks), a sharpie marker, and ferric chloride from Radio Shack. IC footprints could be done with rub-on transfers, which even provided alignment holes for the drill. #60 bits could be had at ACE hardware. I still have material and still make stuff that way. Some of it always will.
Don’t try to design a board you’re going to send out for fab in one sitting. Leave it for at least a few days and come back.
You could make a ground plane on one side of the board that has all the power grounds connected to it. Then have a ground pour on the top layer for the signal ground. Join the two at the OUT- terminal.
You can also make slots/moats in the ground plane to keep one area 'clean' and another 'dirty'. Joint the two at the OUT- terminal.
Finally, if you think through where the large and dirty currents flow you can with careful component placement put the sensitive/clean grounds on a part of the ground plane that's furthest away from the higher current densities.
I've used all these methods with good results.
Also note that in a basic LM3886 amp it's only 2-3 nodes that need to connect to a clean ground. You could just put them near each other and connect them on the top layer with a small pour that then goes to the OUT- terminal where it joins the ground plane (on the bottom layer) that has all the other grounds in it.
Tom
Yep. Another valid approach. Works as long as you don't have to build too many channels. That type of layout is no guarantee that you'll get the layout right, however.
Tom