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Old 20th February 2005, 12:54 PM   #1
wxn is offline wxn  Lithuania
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Default LM3886 pcb approval wanted

Okay, so this is my best pcb so far.
There is one pseudo ground star in it but I think it was not necessary as there are no large currents flowing (speaker ground returns to main capacitors).
I also left some space around the chip itself to allow more ways of mounting it to a heatsink.
There is of course an inductor wound around R7.
Signal and power grounds can be separated by shorting or removing the gnd_conn jumper.
Or it could be replaced with a 10ohm resistor (ground lifting iirc).
Btw, LM3886 GND pin belongs to signal or power ground?
Any ideas and suggestions welcome.
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Old 20th February 2005, 12:57 PM   #2
wxn is offline wxn  Lithuania
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And the pcb itself
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Old 20th February 2005, 12:57 PM   #3
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I'm new to diy amplifiers, but 10 ohm in series at the output?
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Old 20th February 2005, 01:02 PM   #4
wxn is offline wxn  Lithuania
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Earlier version of the same thing:
http://www.diyaudio.com/forums/attac...amp=1102964769
This one is much simpler and (probably) less stable. But anyway.
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Old 20th February 2005, 01:04 PM   #5
wxn is offline wxn  Lithuania
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Quote:
Originally posted by breez
I'm new to diy amplifiers, but 10 ohm in series at the output?
As mentioned, there is (not shown) an inductor that effectively shorts the resistor out at low frequencies
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Old 22nd February 2005, 05:08 AM   #6
wxn is offline wxn  Lithuania
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Anyone?
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Old 22nd February 2005, 06:59 AM   #7
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It's pretty good.

C10 is unnecessary. C7 is enough but it doesn't matter if you have C10 also.

C9 is also probably not so important and it have to be "tuned" for really compensate the input capacitance, which is the purpose of it.

I'm not totally happy about your long ground trace and C2, C4 at the end. Somehow I have tjhose caps be "closer" the LM chip. It's probably nothing to worry about but in this sense I like the BrianGT's board more (and mine also of course ).

We have both doublesided boards so this make things more optimal, I know.
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Old 22nd February 2005, 07:12 AM   #8
digi01 is offline digi01  China
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i agree with P-A,the ground trace is not too good.

FYI:
here is my non-inverted LM3886 layout,
http://www.diyaudio.com/forums/showt...399#post541399

sch file,
http://www.diyaudio.com/forums/showt...078#post499078

zang
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Old 22nd February 2005, 08:18 AM   #9
wxn is offline wxn  Lithuania
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Quote:
Originally posted by peranders
It's pretty good.


Thanks

Quote:
C10 is unnecessary. C7 is enough but it doesn't matter if you have C10 also.

C9 is also probably not so important and it have to be "tuned" for really compensate the input capacitance, which is the purpose of it.
While they are not essential, they surely won't hurt anyone. And all of the mentioned components could be simply left out.


Quote:
We have both doublesided boards so this make things more optimal, I know.
Exactly. Unfortunately, making double sided PCBs is very difficult with my tools and skills.
Thank you both for your input.
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Old 22nd February 2005, 08:26 AM   #10
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Doublesided pcb with only ground plane is quite easy.

Click the image to open in full size.

When you etch, put tape, any kind but wide tape is the best at the groundplane side, the solderside in your case I think, easier. Etch the board. After ecthing, remove the tape and drill the holes which shall not be in the groundplane. See my picture
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