need help with lm3886 pcb

[andrewabelas]

hi,

i'm a complete noob.. please help me find how to get the my circuit board to work..

i bought a lm3886 circuit board from ebay

Audio Powered Subwoofer Amplifier Kit Based on LM3886 on eBay (end time 27-Feb-10 02:07:19 GMT)

i want to put this amp in my car but i have no idea where i have to input the power from...

please help!

thanks

[ratza]

It won't work in the car, the voltage is way too low.

[andrewabelas]

Originally Posted by ratza

It won't work in the car, the voltage is way too low.

thanks for your reply, how can i hook it up at home then?

[ratza]

I'm afraid you'll need a SMPS to rise the voltage from 12V to +/-25V. Don't buy it if you intend to use it in the car. There are other suitable chips for that.

[Bone]

For home you will need a transformer with either 2 x 25volt output windings or one centre tapped 50 volt winding. i.e. 25 - 0 - 25.

[pacificblue]

The transformer voltage depends on the speaker impedance and the output power you want or need from this amplifier. The datasheet recommends ±28 V for 4 Ohm operation, which means you should not choose a higher than 2x20 V transformer. A 2x25 V transformer would be okay with an 8 Ohm speaker. In either case you will need a beefy heatsink with the non-isolated LM3886 that is shown in the photos. If you have the isolated package, go for 2x18 V with 4 Ohm and 2x22 V with 8 Ohm.

Don't expect the amplifier to deliver anything near 100 W. It is specified for 68 W into 4 Ohm and 50 W into 8 Ohm maximum and that is already pushing it.

You should also take the capacitor voltage rating into account. There are 25 and 35 V types in the photos. If you have used 25 V types, do not use a transformer with more than 2x15 V. With 35 V capacitors, use a transformer with maximum 2x18 V.
The rectifier in the photo does not look up to the job. If you cannot squeeze a bigger one in, put a bigger one off board and connect it with wires to the PCB.