Beginner needs advice on LM4766

Aidan135711

Member
2008-02-10 11:40 am
Hello Everyone.
I want to make a 5 Speaker (FL,FR,SUB,SL,SR) amplifier with 3 LM4766T's which I got from a faulty DVD player.It wil be driven from my pc which has all sorts of outputs on it.I have some questions that need answering as I am not experienced in this area,and have not found much about this IC on this forum or the net except the datasheet.

1.Do I need a pre-amplifier or will pots/stepped attenuators do?

2.Does signal ground and power ground all go to one star point?

3.Is the star point connected to ac supply earth?

4.Do I need a Zobel network?(The amp in the DVD player had them on all outputs)

5.Does the sub amp need some kind of filter or does the PC out-put already do this?
 
Aidan135711 said:
Hello Everyone.
I want to make a 5 Speaker (FL,FR,SUB,SL,SR) amplifier with 3 LM4766T's which I got from a faulty DVD player.It wil be driven from my pc which has all sorts of outputs on it.I have some questions that need answering as I am not experienced in this area,and have not found much about this IC on this forum or the net except the datasheet.

1.Do I need a pre-amplifier or will pots/stepped attenuators do?
Neither is necessary, but input filter caps are necessary for computer sound card use. Pots are a nice simple way to adjust and also some protection.

2.Does signal ground and power ground all go to one star point?
Once met, the grounds never meet again. Please avoid ground loops. See the many examples here, available with a search.

3.Is the star point connected to ac supply earth?
It is rarely done, and when it is, the earth connection point is about 2 inches away from chassis ground.

4.Do I need a Zobel network?(The amp in the DVD player had them on all outputs)
Zobels are helpful whenever there are long speaker cables.

5.Does the sub amp need some kind of filter or does the PC out-put already do this?
The PC should already do this. Why not plug in some headphones and see if that particular channel outputs only bass?

See also: http://cache.national.com/ds/LM/LM4766.pdf

Have fun! ;)