Single layer LM3886 planning for PCB samples

[kuldeepsingh]

LM3886 amp enigma.MP4 - YouTube

DIY Audio Amplifier Blog: LM3886 finished modules

[Pixo]

What can i say, you can never have "enough" amps

These should compliment your existing setup very well.

Where can i get those 10000uF Samsung capacitors in Chennai?

[kuldeepsingh]

Thanx Pixo...

10000uF i got from Ritchie street. but preety costly. where as chinese make suscon make is half the price.

[kuldeepsingh]

Got PCBs for my second design of LM3886 PCBs. Really happy to see the fabricated PCBs. Kind of a dream come true

[AndrewT]

It looks like you have taken on board very little of the advice that is offered.

[Adrianu]

How about this design:
[img=http://s8.postimage.org/ovpg3qyr5/lm33.jpg]

[gootee]

The entire right side needs a ground plane on the side oipposite the signal traces, or, at the very least, fill everything with a "ground pour" of copper so that there is absolutlely-minimal space between the signal and signal ground conductors, everywhere. Otherwise you will have a good antenna for the hum from the AC Mains and transformer secondary wires, which also need to be tightly twisted, everywhere, so they don't make good transmitting antennas. (See Faraday's Law.)

Also, your small decoupling/bypass capacitors are too far from the power pins. And the +28V one is MUCH too far away. I would also just fill the entire area between +28 and -28 with ground copper.

If you have a 2-sided board, you are definitely not taking advantage of it. ALWAYS use a ground plane, covering one whole side, if you are able to have a 2-sided board. In this case, you will keep the signal and power grounds separate, of course.

[ceteras]

Originally Posted by gootee

Otherwise you will have a good antenna for the hum from the AC Mains and transformer secondary wires, which also need to be tightly twisted, everywhere, so they don't make good transmitting antennas. (See Faraday's Law.)

That is never going to happen. A good antenna for 50Hz, made from a 2inch wire some 10inches away from a proper built mains transformer?
I've never used a ground plane or even a ground ring for an LM3886 amplifier, I never needed it. I even built one "in the air" without a PCB. No hum.
The pcb design shown is just fine. Perhaps the 100n decoupling caps could have been closer to the power pins, but I don't think they're "much too far".
Also I would have put a 10ohm resistor between the power and signal grounds.

[AndrewT]

You don't need a 2layer PCB.
You don't need a Ground Plane.
You don't need any pour fill.

Get the traces for every FLOW & RETURN pair very close together.
That reduces the loop area. That is by far the most important parameter: LOW LOOP AREA.

[gootee]

Originally Posted by AndrewT

You don't need a 2layer PCB.
You don't need a Ground Plane.
You don't need any pour fill.

Get the traces for every FLOW & RETURN pair very close together.
That reduces the loop area. That is by far the most important parameter: LOW LOOP AREA.

Of course. But the best ways to accomplish LOW LOOP AREA are, in order from best to worst:

1) 2-sided pcb with ground plane opposite signal traces
2) 1-sided with copper pour to fill ground around signal traces and pads and under signal components
3) 1-sided with existing signal and signal ground traces moved closer together.