Join Date: Mar 2002
Location: Austin, TX, USA
My figures were off, so I edited the post with new info...
1 channel of a 100 watt amplifier will draw approximately 17 amps RMS on the peaks. If you have a 4 channel amp, multiply the number by 4. But this is the absolute maximum rating. Chances are you aren't going to be seeing 4 X 17 or 68 amps continuous. But never the less the current draw is substantial.
Be sure to run some sizable cable from the amps to the battery. Install fuses in both the positive and negative circuits. I suspect 60 amp fuses will work fine despite the peak load being greater (for a 4 channel amp). But if the 60 amp fuses blow, install a size larger.
The reason you want to connect straight to the battery is two-fold. First, you need substantial current carrying ability. Second, you want clean power. If you use the frame or body as a ground, you are going to amplify noise from turn signals, alternator, and ignition.
Fusing both the hot and ground are important as well. It may seem odd to ground the negative. The reason is that since when you have a good ground connection to a high current load, if the engine ground becomes flaky, the starter will try to ground itself through your amps. Without the ground fuse, you can easily vaporize the ground traces off the PC board inside the amp.
Many people attach their amps to the back of a wooden speaker box. The benefit is you isolate the amp ground to your beefy ground which isolates the noisey environment from your amp circuit.
A cheap way to make amp cables is to buy a heavy duty orange extension cord at your local home store. You can pick up a pretty good one for less than 15 bucks. Then use large permanant markers to stripe your hot and ground red and black respectively. Any easy way to do this and make it look professional is to drill a couple holes perpandicular to each other in a chunk of 2 X 4. Run the wire through one hole and stick the permanant marker in the other. A rubber band can be used to keep the marker firmly in contact with the wire. Then pull the wire through the block and it will have a nice purty stripe on it.
Once it is all cut to length, twist all three wires together on an end and crimp or solder on a large copper lug. If you do it right, it will look like one huge orange cable. The white, black, and green conductors will be hidden by the terminal. A piece of black heat shrink will ensure the connection is hidden and professional looking.
[ 08-29-2004, 09:21 AM: Message edited by: dnult ]
68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI