2 8's AKA Jeepbeats

iTrader: (19)

Hey, I found this on the Rockford site, it is from Autosound 2000. Sorry about the length of it, you might have to copy it and paste it into Word, etc. Might help some people out in tracking down and solving noise problems though:

AUTOSOUND 2000's
QUICK CHECK FOR TROUBLESHOOTING
CAR AUDIO SYSTEMS
Preface:
All audio systems exhibit noise; however, if the level of noise is low enough, and the signal level high enough, noise
should not be a problem. This means that it is very important that the signal level throughout the system be optimized
BEFORE dealing with your noise problem. Using a scope (or a small portable amplifier) and Track 99 (1kHz at all high
bits) of Rockford Fosgate CD RF-CD101 (Autosound 2000's CD #101) or Tracks 24 through 29 of Rockford Fosgate CD
RF-CD102 (Autosound 2000's CD #102), adjust the system so that when the maximum usable signal level of the deck
is fed into the system, all the preamp level components clip at the same time. However, we recommend up to as much
as a 3:1 voltage overlap with the power amplifiers; i.e. an amplifier with a 2 volt minimum sensitivity can be driven by
up to 6 volts of signal.
Noise Overview:
Car audio electrical accessories are notorious for interfering with car audio systems. The interference commonly arises
from three areas:
1) Power line noise (5%), which can be attenuated with in-line noise filters,
2) Inadequate power supply isolation (45%), which can be cured with transformer signal coupling, additional isolated
power supplies, or changing out components, or
3) Inductive interference (45%) – including loop area inductive noise picked up by the signal cables – which can be
remedied by relocating or rewiring components, rerouting signal cables, or using twisted cable or balanced transmission
systems.
Autosound 2000 1-2-3 Method of Logical Troubleshooting
I. MUTE THE AMP(S). Insert a muting plug (shorted male RCA connector) into each amplifier channel. Turn up the
amp sensitivity. Start the car and turn on the headlights, air conditioning, brake lights, etc. Listen for noise in each
speaker. Be very picky here!
A. If still noisy, substitute a small test speaker with short leads for the speakers, crossovers, and speaker leads in the
car. If still noisy, substitute an isolated power supply (120 VAC to 13.8 VDC bench supply or a small motorcycle
battery) for the car's alternator. If the amplifier is noisy with the test speaker, you have a BAD amp. Send
it in. It really doesn't matter if it is quiet or noisy while running on the isolated supply because you have a BAD
amp. Send it in for repair and if it was quiet on the isolated supply, indicate so on the repair tag.
B. If your muted amp is quiet, you've just joined 99.5% of car audio. Amps are usually very clean and do NOT
pick up unwanted noise! Continue on to Step II.
II. DECK TO AMP. Using a new set of signal cables, connect one channel from the output of the deck directly into one
channel of your clean amp. Run the cables outside the car and as far away as possible from the metal of the car. (For
noise purposes, consider a 2" thick cushion of electromagnetic energy emanating from every metal surface in the
car.)
A. If still noisy, congratulations, in all probability your equalizer, electronic crossover, DSP, whatchamacallit, are
just fine. This means that you can't get your deck playing quiet with your amp, right? Go to Step III.
B. If all is quiet, congratulations, in all probability your deck and amplifier(s) are fine – you obviously have a
problem with your equalizer, electronic crossover, DSP, etc. Skip on down to “Time for the Processors.”
– 45 –
III. MOVE THE DECK. If you're at this step, it's time to turn your system into an “amplified deck” by temporarily
relocating the deck right ON TOP of the clean amplifier. Then using very, very short signal cables, connect the
output of the deck into the input of the amp and test for noise. Play a zero bit track – silence – and make sure all is
completely quiet.
A. If still noisy, you're in a heap of trouble. We suggest that you try another deck and give us a call so that we can
put your name into the record books. It's a bad car audio day for you.
B. If the deck is quiet, then congratulations, you're on your way to a successful installation. It is now time to
slowly, methodically, reinstall the deck back into its final position. Test for noise each step of the way. If the
noise returns, suspect the signal cables. Forget shielding because it will have only a very, minimal effect within
the audio band. We highly suggest using twisted pair cables (Monster Cable 401-type or equivalent) or a
balanced transmission system for cable induced noise.
Time for Processors:
By the end of Step III, you should have the deck playing quietly with the amp, with the quiet cables quietly routed. So
it's time to add the signal processors – one at a time – back into the system. Simply repeat Steps II and III with the
equalizer, then the electronic crossover, etc. However, before MOVING THE SIGNAL PROCESSORS to the amplifier,
we highly suggest that you power the noisy process from an isolated power supply rather than the car's +12 volts DC
and chassis ground. Make sure to also connect the turn-on lead to the isolated power supply. If the processor is now
quiet, then it is highly probable that the component has inadequate isolation. Solutions include changing components
or permanently adding an external isolated power supply (Call Autosound 2000 at 209-465-3450 for info on isolated
power supplies).
Summation:
During the design stage of your vehicles, try to avoid using extra batteries and high output alternators. Extra batteries are
nothing but loads as soon as the engine is started and high output alternators usually make more noise than stock
alternators. Also, extra batteries installed in the trunk of a car will ALWAYS force extra ripple current to flow over the car.
Install Stiffening Capacitors® as close to the power supply input of your amplifier as possible. The big caps will feed the
switching power supplies of your amps and minimize the inductive losses in your power wiring. Plus, they will help
your peak system response.
In problem cases, we highly recommend the use of twisted pair cable rather than coaxial cable for RCA leads. This
practice will greatly minimize cable induced noise – especially in four channel amps!
Don't forget that your system is only as good as its worst component. Do NOT use components with inadequate power
supply isolation or you will be asking for problems.
The best electrical ground on a car is the CHASSIS of the car. Do NOT run ground leads up to the case of the alternator
or the negative battery post. Keep ALL ground leads as short as possible.
With properly isolated components, it does NOT matter where the component is grounded. We're sorry to say that with
inadequately isolated components, it matters! With poorly isolated components, different grounds can cause different
noises.
The deck is the signal reference ground for the entire sound system. The deck usually has THREE connections to the
car's chassis: The black ground lead, the base of the antenna, and the metal-to-metal bond between the case of the deck
and the chassis of the car. With three grounds, there is usually NO cause to worry about the ground of a deck.
Amplifiers are usually designed with adequate power supply isolation. This means that it should not matter where a
deck is grounded. (Decks are grounded three times and amps float. This is car audio!)
The more components installed on a signal path, the more chances for noise to enter a system. The more electrical
accessories on a car, the more noise will be produced by the alternator.
This information was compiled from more than 20 years of working in car audio. If you would like more information on
this topic, or any other technical aspects of car audio, please call 800-548-8200 and ask for a subscription to Autosound
2000 Tech Briefs — the monthly magazine for the technically inclined.

Speakerman

holy shi* man. I read like 4 lines and said fuc*it...cant be that important. lol

2 8's AKA Jeepbeats

iTrader: (19)

True true, unless you have a noisy system..... [img]graemlins/thumb.gif[/img]

timmyturtle

iTrader: (8)

Hey,

Thanks for the post. I just installed an in dash eq and am noticing alot of hiss up front (is this pink or white noise?). Dernit! Is this common?

sac

Excellent post. I have noise problems with my Altomobile processors. I may not be able to fix these problems, but this helps me determine whether I will.