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LM3886 Layout ok?
LM3886 Layout ok?
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Old 26th December 2017, 09:26 AM   #101
sevenup2278 is online now sevenup2278  Netherlands
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Some time ago I also started with a LM3886 layout.
Never finished, but maybe I will continue after reading this tread, some good information here. Still need to beef up the power traces and add groundplane(s).
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Old 26th December 2017, 09:58 AM   #102
00940 is offline 00940  Belgium
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To have only one connection between power and signal ground, I wouldn't connect the ground of J1 to the top groundplane.

BTW it's easier to understand a PCB if you don't mirror the bottom.
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Old 26th December 2017, 10:10 AM   #103
bozoc is offline bozoc  Croatia
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Quote:
Originally Posted by 00940 View Post
To have only one connection between power and signal ground, I wouldn't connect the ground of J1 to the top groundplane.

BTW it's easier to understand a PCB if you don't mirror the bottom.
Yep, that is correct. Was planing to do that, can't believe I missed that one.
Thank.you on that!
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Old 26th December 2017, 04:02 PM   #104
bozoc is offline bozoc  Croatia
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Quote:
Originally Posted by sevenup2278 View Post
Some time ago I also started with a LM3886 layout.
Never finished, but maybe I will continue after reading this tread, some good information here. Still need to beef up the power traces and add groundplane(s).
I am new to this but I recommend you read the following material several times as it helped me a lot:

TI Datasheet

tomchr's guide on LM3886

Wikipedia on operational amplifiers

Various lm3886 diyaudio threads



The layout you have is pretty much point to point wiring.
I would start with the new layout.
Keep attention to grounding layouts(reduced loops, separated signal and GND layout that connect the the speaker out) and supply decoupling as they are vital to LM3886 performance as those are vital if you want to achieve LM3886 datasheet performance.
Happy diy-ing!
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Old 27th December 2017, 05:46 PM   #105
sevenup2278 is online now sevenup2278  Netherlands
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Quote:
Originally Posted by bozoc View Post
I am new to this but I recommend you read the following material several times as it helped me a lot:

TI Datasheet

tomchr's guide on LM3886

Wikipedia on operational amplifiers

Various lm3886 diyaudio threads



The layout you have is pretty much point to point wiring.
I would start with the new layout.
Keep attention to grounding layouts(reduced loops, separated signal and GND layout that connect the the speaker out) and supply decoupling as they are vital to LM3886 performance as those are vital if you want to achieve LM3886 datasheet performance.
Happy diy-ing!
I added the groundplanes and beefed uo the high current tracks.
Not sure where to connect the power groundplane to the signal groundplane though.
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File Type: jpg bottom.JPG (318.6 KB, 129 views)
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Old 27th December 2017, 07:01 PM   #106
AndrewT is offline AndrewT  Scotland
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The only component that crosses over the cut between the planes is the chipamp.
Or is there a component that I can't see crossing over?
That points to the trace under the chipamp as the place to make the connection.
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Old 27th December 2017, 07:20 PM   #107
terrences is offline terrences  United States
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sevenup2278
I agree that tomchr's guide on how to tame these LM chips is definitive but why remake what's already been done? Use what you learned and make your board for the LM3875. Better still, make it compatible with both LM3875 and LM3886
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Old 27th December 2017, 08:26 PM   #108
sevenup2278 is online now sevenup2278  Netherlands
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Quote:
Originally Posted by AndrewT View Post
The only component that crosses over the cut between the planes is the chipamp.
Or is there a component that I can't see crossing over?
That points to the trace under the chipamp as the place to make the connection.
Yes, the LM3886 is the only part crossing the split between the planes. Thanks for the insight.
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Old 17th January 2018, 05:17 PM   #109
bozoc is offline bozoc  Croatia
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Default LM3886 Preamp

I made PCB for LM3886 few posts before.
This is the schematic
Click the image to open in full size.

I would also add volume control with current buffering after the potenciometer. Buffer would be something like OPA2134 and and lm317 to drop the voltage from the +-30V main amp psu.
So just a basic and simple board that goes - input/potenciometer/opmap that wires to the amp board.

Are there any more modern op amps that would server this purpose and are there better solutions to bringing down the +-30V for the buffer supply?
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Old 17th January 2018, 05:23 PM   #110
tomchr is offline tomchr  Canada
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LM317/337 are fine regulators for that purpose.

OPA1612, OPA1642, LME49720 all spring to mind as modern opamps.

Tom
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