LM3886 Amplifier Board

Community PCB Design
48

bigglez:

SpikedCola:
I made up a master board. It will attach to two slave boards (the other two amps). This look a bit better in terms of layout and trace size?

Yes! Much better. Still a couple of issues to address:

(1) You can’t use 25mil square pins for high power audio or DC

(2) You can’t place inputs and outputs of an amp on adjacent pins

(3) You can’t sum three amplifier modules into one as shown

Start by removing all the 25mil square pins and using

proper screw terminals rated to at least ten amps.

[Something like this.

For a 50Watt amplifier module you will draw about 75Watts

from the DC supplies. At sixty volts you have to deliver

over one amp without local heating or high inductance,

both of which reduce reliability.

Keep the input signal and it’s ground well away from

the output signal and power ground.

In the original design the three amplifier ICs were summed

with 200milliohm resistors, to a common load terminal. The

cables and connections to the summing point will need

to be much lower impedance (such as the fat trace/tracks

on the original board). If one (or two) go to a higher impedance

the remaining amplifier will be overloaded.[/quote]
Points noted. Ill make the changes when my flight gets in tonight. Thanks!

Also, in terms of connecting the boards together, should the summing resistors be on the master board or on the slave boards? I was hoping to use a larger conductor (~14ga) to hook the outputs of the slaves to the master to make up for having separate boards, but Im not sure if it will work. Again, this is all a learning experience for me, so thanks for taking the time to help! (all of you)

Shifted:
It also looks like you have the positive side of the two large rightmost caps connected to the ground trace on the bottom…

The - end of the cap is hooked to the V- trace (-30v) so the polarization is correct :)

Shifted:
What is the voltage/current rating on the SMD cap you have connected to the huge power trace? (upper left hand corner, can’t read the number).

I havent actually picked components yet, I just guessed at the components I would be using, assuming I can change the package and board layout later on if I come across something. However, I think I may need to rethink that (and the other 0.1uF caps) as the original design calls for Wima 63v caps](http://tinyurl.com/9casb2)