LM3886 pcb approval wanted

wxn · 20th February 2005, 01:54 PM

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.

wxn · 20th February 2005, 01:57 PM

And the pcb itself

breez · 20th February 2005, 01:57 PM

I'm new to diy amplifiers, but 10 ohm in series at the output?

wxn · 20th February 2005, 02:02 PM

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.

wxn · 20th February 2005, 02:04 PM

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

wxn · 22nd February 2005, 06:08 AM

Anyone?

peranders · 22nd February 2005, 07:59 AM

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.

digi01 · 22nd February 2005, 08:12 AM

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

wxn · 22nd February 2005, 09:18 AM

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.

peranders · 22nd February 2005, 09:26 AM

Doublesided pcb with only ground plane is quite easy.

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

20th February 2005, 02:02 PM	#4
wxn diyAudio Member Join Date: Sep 2003 Location: Vilnius	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. __________________ Nothing is as simple as it seems

22nd February 2005, 06:08 AM	#6
wxn diyAudio Member Join Date: Sep 2003 Location: Vilnius	Anyone? __________________ Nothing is as simple as it seems

22nd February 2005, 07:59 AM	#7
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	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. __________________ /Per-Anders (my first name) or P-A as my friends call me

22nd February 2005, 09:26 AM	#10
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	Doublesided pcb with only ground plane is quite easy. 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 __________________ /Per-Anders (my first name) or P-A as my friends call me

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20th February 2005, 01:57 PM	#3
breez diyAudio Member Join Date: Jul 2004 Location: Finland	I'm new to diy amplifiers, but 10 ohm in series at the output?

22nd February 2005, 08:12 AM	#8
digi01 diyAudio Member Join Date: Mar 2003 Location: BEIJING	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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