Separating them and placing holes for wire/resistor is easy enough. I could put the connection point exactly between the 2 caps at the end of The line from the input ground.
It would be nice to have a seperate signal ground anyways, it will be more versatile.
I think i will make a board after that change, and see how it is.
It would be nice to have a seperate signal ground anyways, it will be more versatile.
I think i will make a board after that change, and see how it is.
By the way everyone thank you for helping me with the design, although I appreciate P2P may be better sound.
I feel more comfortable using a circuit board for now. So i am just trying to make it as best I can using what i heve read here.
I can not believe how much i have learned here! you guys are great!
P.S felix sorry for hi-jacking your thread!
I feel more comfortable using a circuit board for now. So i am just trying to make it as best I can using what i heve read here.
I can not believe how much i have learned here! you guys are great!
P.S felix sorry for hi-jacking your thread!
I don't agree that ground planes are not suitable for power amp or any other audio circuits. They only add less than 1pF stray cap to other PCB traces, but the reduction in ground path reactance far out-weight this. As long as the sensitive pins, pin1, pin8 and pin3 in the case of LM3875, are kept out from the ground plane (1mm clearance is enough), stray cap is not an issue.
But the concept of star ground still valid even if there is ground plane. Return current for small signal, large signal and power supply shall be separated into different local ground planes and be jointed together at the star.
My 0.5 cents.
Below is my LM3886 PCB.
An externally hosted image should be here but it was not working when we last tested it.
"As long as the sensitive pins, pin1, pin8 and pin3 in the case of LM3875, are kept out from the ground plane (1mm clearance is enough), stray cap is not an issue."
-why is pin 1 sensitive? there will be a lot of capacitance to ground anyways.
also, you can etch a small trace around the top of the ground plane on the sensitive areas to reduce the capacitance. you reduce the ground plane, but this would be a small area.
i would have thought 3 7 and 8 would be the criticle pins.
-why is pin 1 sensitive? there will be a lot of capacitance to ground anyways.
also, you can etch a small trace around the top of the ground plane on the sensitive areas to reduce the capacitance. you reduce the ground plane, but this would be a small area.
i would have thought 3 7 and 8 would be the criticle pins.
hi Upupa Epops,
Do you mean the middle to the right part of the PCB? The solder joints are fine, but they certainly do not look good. The problem does not come from the solder (or the tin), it is the ground and power plane that suck up lots of heat from my soldering iron. I shall have put the iron onto those pads for a longer time.
If the PCB is for industrial use, I might be asked to add "thermo relief" on those pads. But I don't like "thermos", cos they also block the current flow.
Thanks for the tips.
Do you mean the middle to the right part of the PCB? The solder joints are fine, but they certainly do not look good. The problem does not come from the solder (or the tin), it is the ground and power plane that suck up lots of heat from my soldering iron. I shall have put the iron onto those pads for a longer time.
If the PCB is for industrial use, I might be asked to add "thermo relief" on those pads. But I don't like "thermos", cos they also block the current flow.
Thanks for the tips.
Hi banana, you don't need " thermo relief ", you need powerful soldering iron or longer time of soldering, belive to " old dragon " 
. Right soldered pad looks like " Fudjijama from the plane " , not like " Mont Olympos on Mars " and all is about right temperature by soldering . If is too low, tin around soldered wire do little " crater " and it is seen on practical all pads, what indicated that soldering will be unreliable. Also you cut wires too short - you must cut it little bit up the " tin volcano " - tin must do around wire the same curve like stones on slopes of volcano ( capilar elevation ) 
.
. Right soldered pad looks like " Fudjijama from the plane " , not like " Mont Olympos on Mars " and all is about right temperature by soldering . If is too low, tin around soldered wire do little " crater " and it is seen on practical all pads, what indicated that soldering will be unreliable. Also you cut wires too short - you must cut it little bit up the " tin volcano " - tin must do around wire the same curve like stones on slopes of volcano ( capilar elevation ) .Thanks again. I did a lot of soldering at work, but mostly SMD. And I have no problem soldering normal size pads, but those large pads really drag my soldering iron's power. Maybe I do not have enough patient stirring my soldering iron around the pad long enough. "Thermo relief" do help, but it is not my choice.
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