New Lm3886 PCB - please review

[diarav]

Hi,

Attached is my Eagle PCB layout of Rod Elliots Chip Amp (P19).
Single Chip 50W Stereo Amplifier

I have tried to modify this manually (using MS Paint) to add make the ground track fill the PCB as shown in attachment. I have seen this on other PCBs and not much on chip amps. Is this acceptable? Would it have any adverse effect (hum, noise etc)? Appreciate your response and any other feedback.

Thanks in advance.

[abraxalito]

If you would like it to sound good, you'll need to pay more attention to the grounding than this - a single fill just won't cut it.

[diarav]

Originally Posted by abraxalito

If you would like it to sound good, you'll need to pay more attention to the grounding than this - a single fill just won't cut it.

abraxalito: Thanks for your response. As such I am not an expert on these. So you think I might want to stick to my Eagle layout itself. I have tried the star ground on my Eagle layout.

[abraxalito]

Originally Posted by diarav

I have tried the star ground on my Eagle layout.

If by the Eagle layout you mean the original one without the thickened tracks, then it doesn't look to me as though that has a star ground.

In getting the best layout for a chipamp, the power supply and the amplifier pcbs have to be considered together as a system. If you adopt the twin bridge rectifier approach then the star point can be on the amplifier pcb, otherwise with a centre-tapped power supply I'd make the star ground on the PSU board.

[Maxxtr0]

Hello diarav,

maybe you might also read my old thread with exactly the same topic! There you can find some hints on designing a LM3886-PCB

You can find it here: LM3886 Layout ok?

Greetings,
Max

[diarav]

abraxalito: Thanks for the clarification on the star ground. I always confused star ground to be a point where all ground connections converged (Circled in attachment). I guess I'll make the audio ground outside the PCB and get the points to the input and speaker directly from the 0 tap of the 35V-0-35V supply.

Maxxtr0: Thanks for the link to the post. A lot of information and some nice layouts there. Seems like some more work to do on my PCB.

[yatgai]

Diarav

I am also working on the LM3886 based chip amp. My board layout attached. The PS is snubberized unregulated one with 2x4700uF capacitors per rail

Any comments / suggestions welcome

Thanks

Yatin

[sasmit]

Originally Posted by yatgai

Diarav

I am also working on the LM3886 based chip amp. My board layout attached. The PS is snubberized unregulated one with 2x4700uF capacitors per rail

Any comments / suggestions welcome

Thanks

Yatin

One pretty obvious one is you're using too much real estate on your pcb. you could make a much more compact one. Pad sizes for the resistors are going to be a problem if you actually make the pcb , you need larger size pads other wise the drill will end up eating up most of the pad. With so much space you could have used much thicker power traces and speaker traces. You could keep the 2200uF a little farther away and add smaller electrolytics ~ 10 Uf's near the chip pins along with 0.1uf's.

[diarav]

Originally Posted by yatgai

Diarav

I am also working on the LM3886 based chip amp. My board layout attached. The PS is snubberized unregulated one with 2x4700uF capacitors per rail

Any comments / suggestions welcome

Thanks

Yatin

Yatin,

Board looks good. I am still a novice in electronics, so would not be able to comment much on technicalities of your layout.

Where did you get the LM3886 eagle libraries? I saw someone else also use the LM3886 round pads as your layout. I am using the lmopamp.lbr from the eagle website. Can you share the lbr or the links for the same?

[yatgai]

Diarav

I think the layout of LM3886 is in the attached .lbr file, I am still not expert in eagle. you can give a try by copying the .lbr file in folder lbr under eagle

sasmit

The power and output trace is 2.5mm thick, I will be using 24-0-24 AC transfo which will give about 33.6V DC, do you feel that 2.5mm thick will be inadequate ?

Also 1) how do I add pads under the component holes ? at present I am using the via for the holes. 2) is there any way in eagle to see only the traces and not components thereon ? at present I am copying the file by another name and delete the components in new file, this I feel is long way around.

Incidently I am using free version of Eagle.

Thanks all for your support

Regards

Yatin