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Message: <blockquote data-quote="onecoolee" data-source="post: 3621329" data-attributes="member: 583404">As an EE and former USAC/IASCA competitor and part-time car audio installer, I have seen ground loop issues many, MANY times.  To be completely honest, they aren't always easy to avoid.  Think about it... most installs are simple--consisting of a head unit and amplifier(s)... I have rarely seen ground lopp issues in these installs, but they can still exisit.  Most installers do not use the same ground point for the head unit and ampliefiers, which is really the easiest way to avoid a ground loop.   The entire chassis of the vehicle is ground, BUT, there are differences in potential all over the place...A complex install might consist of a headunit, 2 or 3 signal processors or an EQ/xover, and amps--all of which are probably grounded to different locations on the chassis... this type of instlal is always subject to noise issues... some of which may be pops, clicks, buzzes, alt whine, etc.  If the ground point is not the same for every piece of equipment, its best to make sure that there are not huge differences in potential between ground points... you can do this by take an ohm meter and setting it to the 20 ohms scale, and making sure that the only difference in resisitance that the meter is reading is within the leads... touch both leads together and it will read like 0.8 ohms.  Then, touch the head unit ground point with 1 lead, and the singal processor ground point (Or amp ground point) with the other lead... there should be the same reading as if you touched the 2 leads together... that means that there is no major resisitve change in the ground point from the head unit to the signal processor or amplifier ground point, and thus there should be no difference in potential either.  You can also measure the resistance from each ground point directly back the ground post on the battery, and both points should yield the same result.By doing this, there aren't any ways for noise to sneak into the system and ride on the signal lines like its explained above.  Induced noise can happen too, but that easily avoided by keeping your speaker and RCA lines away from noises components, like underdash computers, and any other lines that may be emitting an AC inductive signal which can couple itself to an adjacent line.  Try to cross lines with fluctuating voltage at a 90 degree angle to reduce the amount of coupling between their paths.Components in general, if poorly designed, can cause huge issues with noise problems... in car audio, like most everyhting in the world, you get what you pay for, and an el cheapo amp, with a poorly designed power supply, can make the signal side of the amp noisy... the same goes for EQs, and other processors.  Plus the more processors you put in series, will only amplify your noise, as soon as noise is prevalent within the system.  So watch your gains too and set them properly being sure that you aren't boosting noise, or clipping the good signal in your system... if you bump up your gains too high, you are amplifying the signal with the noise component in it, which can make an expensive system sound terrible.  So, proper tuning can make a system sound great, and can clean up the noise too...Another means of avoiding noise is by using a high volt output head unit (4V+), or a signal processor which will amplify the signal voltage before noise is on the signal lines...then this elevated signal strength is fed to processors or your amp(s), as a higher level (or higher effective gain), and thus a cleaner signal.  This allows you to use less gain on your amps, because the signal being sent to them is already boosted... and the amp isn't having to amplify the signal; plus the noise on the line.  Most good headunits output at least 2volts these days, and some do 4V or higher, which always helps.Good quality RCA cables are important too... don't buy a $1000 amp and a $3 single shielded RCA cable... if you can afford the expensive amp, buy a decent cable too--something with dual shielding or even twisted pair signal transmission to avoid noise issues... yes, twisted pair cables can help... since the noise can effectively cancel itself out in this configuration.  BE careful where and how you run your RCAs too... induced noise is easy to get into a system if you aren't careful where the RCAs are run.  Always be sure that the jacket of the cable is not pierced or touching ground... Grounding the RCAs signal shield to the car is an immediate source for MEGANOISE !  You will know if this is your problem in most cases...A good installer will do all of the above, making sure to minimize and noise issues.  By following good grounding practices, using properly designed equipment, and good RCA cables that are run in a manner to avoid induced noise, alot of the issues being discussed in this thread are easily avoidable.</blockquote>

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