Table of Contents
Advertisement
AUTOSOUND 2000 TROUBLESHOOTING TIPS_
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 Autosound 2000's CD
#101, or tracks 24 through 29 of Autosound 200'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.
page 34
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."
III.
MOVE THE DECK. If you're at this step, it is 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 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
supply power to the noisy processor from an isolated power supply rather than the car's +12 volt 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).
page 35
Advertisement
Table of Contents
