LM3886 68W amplfier:

Description:
The LM3886 is one of the most popular gainclone chip amps. It features high power (68WRMS, 135W peak) into a 4-ohm speaker, mute, and simple circuitry, making it an excellent choice for the beginner and professional alike.

I would like to thank bigparsnip from the DIYAudio Forums for designing this PCB and schematic and allowing it to be posted on electroNET.

Schematic:


PARTS LIST:
Part # Description
R1 Varies depending on Power Supply Voltage - See datasheet
R2 50K - 1/4W 1% tolerance
R3 1K - 1/4W 5% tolerance
R4 1K - 1/4W 5% tolerance
C1 100UF - Polarized electrolytic
C2 22uf - Ceramic or similar
C3 0.1uf - Polypropylene or similar
C4 0.1uf - Polypropylene or similar

PCB:


Usage:
Build the amplifier following the schematic and PCB. As always, when testing it, test with a cheap speaker that damage to will not cost much to replace.

If your source is consistantly connected (ex. a pre-amp always connected to the amplifier), you can skip C2 by soldering a jumper in place of it on the PCB. If possible I would highly reccomend doing this to decrease signal path and increase audio quality. However, if your source may ever get disconnected (such as a CD player), it is reccomended that you include C2. If you do not, disconnecting the source will send a large DC current into the speaker and will very likely damage it.


Photos of my amp:

Finished PCB



Amplifier mounted on aluminum plate (this amp is used as a subwoofer amplifier).

Downloads:
Schematic - GIF
PCB Layout - GIF
Eagle Schematic and PCB - Self extracting ZIP (LM3886.exe)

Links:
www.national.com
LM3886 Datasheet