How does one go about making sure that the 12v power supply to an
external amp is clean and free of any possible shorts?

Thanks!

On Fri, 8 Jul 2005 00:44:53 +0000 (UTC),
(Bob) wrote:

How does one go about making sure that the 12v power supply to an
external amp is clean and free of any possible shorts?

Thanks!

The power supply is important, but the ground connection is equally
important, if not more so, so I'll cover both.

For power, use a heavy-gauge connection directly from your battery.
Put a fuse in the power wire as close to the battery as you can, but
no further than 12 or 18 inches from the battery. This is because if
any part of the wire between the fuse and the battery shorts to
grounds, the wire/insulation will catch fire, so you want to keep that
distance as short as possible.

Use a good crimped or soldered terminal to attach the wire to your
battery, the fuse holder, and the amp itself.

Use a flexible wire with abrasion/chemical-resistant insulation, and
anytime you pass the wire through a metal panel like a firewall, use
rubber grommets to prevent chafing. Keep the wire away from hot or
moving parts like exhaust manifolds, belts, pullies, and
seat-adjustment tracks.

For the ground wire, use the same thickness as you used for the power
wire, and run it directly to the battery if at all possible. If you
can run it directly to your battery, you can attach it to a metal
chassis part near your amp. Make sure you scrape any paint or
undercoating off of the chassis to make sure you have a good
connection. Keep in mind that if there's any resistance between your
chassis mounting point and the negative terminal of the battery, there
may be a voltage difference between the two points, which can cause a
"ground loop". Ground loops are the biggest cause of engine noise in
a car stereo, particularly alternator whine.

For my installations, I use a "star" or "single-point" power and
grounding scheme. I run heavy-gauge wire from the battery to the
trunk, where most of my electronics are. The power lead goes to a
fused distribution block, and the ground lead goes to a non-fused
distribution block. From the distribution blocks, I run wires to the
individual components (amps, signal processors, CD changers,
etcetera). I also run smaller-gauge power and ground cables from the
distribution blocks up to the head unit.

This guarantees that EVERY component in my system is getting power and
ground from the same source (the distribution blocks), and the blocks
are getting power and ground directly from the battery.

One last thing - don't mount any of your components directly to metal
panels, as some components will use the chassis as a second ground and
give you ground loops. If you need to, you can mount the component to
a board and then mount the board to the metal panel. This will give
you a secure mount, while keeping the amp or whatever it is
electrically isolated from the car's chassis.

I know doing it this way may seem like overkill, but it will give you
a clean, safe and secure installation, and will eliminate 99% of the
potential sources for engine noise. And believe me, chasing down
electrical noise is one of the most time-consuming, least-fun aspects
of installing a stereo system.

--
Scott Gardner

"I've been accused of vulgarity. I say that's bull****." (Mel Brooks)