Project Help

[KettermanJ]

Im a senior in High School and I'm trying to find a nice amplifier project to build for my senior project. I want it to drive a subwoofer for my car. Any help would be appreciated. Thanks

-Josh

[AndrewT]

Hi,
the single polarity supply of 13.8V (with engine running) limits the output voltage to about 4Vac.
This gives upto 2W into 8ohms, 4w into 4ohms, 8W into 2ohms and 16W into 1ohm.
If you build two amplifiers and bridge them you can obtain twice the power into twice the impedance.
Those same figures become 4W into 16ohms, 8W into 8ohms, 16W into 4ohms and 32W into 2ohms.

If your bass speaker is 4ohm, the maximum power available from a bridged pair of amplifiers is 16W. Choose a very efficient subwoofer AND design each amplifier to drive a 2ohm reactive load. This means each amp of the pair should be safe to drive a 1r0 resistor to full power for a short time as well as delivering high current out of phase with the drive voltage into the reactive load.

This is not a simple design exercise. Do lots of research and selectively assess each part before accepting/rejecting it. It is the research and selection of specification criteria that gain most marks. Evaluation (how you could do it better/differently next time) shows how much you have learnt. The actual making is usually worth no more than 30% of the total marks.

If you want/need more power then save that project for a post school time. Just do enough to drive a 4ohm or 8ohm speaker for the moment.

The big saving is the relative safety of not working with mains voltages.