dkelly

as far as sound quality a good ground loop isolator is accurate to within .5 db across the whole audio spectrum there's nothing inherently wrong with a fix that is easy

EuroDriver

I had very similar problems with my Concert HU and a Blaupunkt digital amp.

Audi design their wiring connections between HU and amp using low impedance unshielded wiring. This is contrary to industry practice which is to have high impedance connections using shielded coaxial cables between HU and amp

I tried to look for impedance matching transformers to install behind the HU but was unsuccessful

For the time being I have given up trying to get the amp to work hiss free and have left it out of the car.

However, visting David Navone's web site today, I see his N-645 might well do the trick to reduce the noise (hiss?)

Let us know how you solve the noise problem.

The other way of course is to get an new HU with a normal RCA pre out but then it won't look so nice<ul><li><a href="http://www.autosound2000.com/linedrivers.html">David Navone Autosound Web page</a></li></ul>

bbaudi382

a good install will not have ground noise.

bbaudi382

converts line outs to rca outs.

MacSub

and connect it to the common pin on the mini-ISO connector ensuring it doesn't touch the RCA signal (left/right) pins. There is the blaupunkt adapter availble that does all this for you and it's not a crappy line out converter so is very small.<ul><li><a href="http://www.caraudiodirect.co.uk/product_info.php?products_id=79">http://www.caraudiodirect.co.uk/product_info.php?products_id=79</a</li></ul>

dkelly

but getting rid of noise created by a ground loop can't be predicted and has nothing to do with the 12v power distribution of the vehicle. which is what all noise filters address. the accepted way of getting rid of noise created by a ground loop is to isolate the grounds. now you can tear the system down looking for a mistake that probably doesn't exist or you can add a gli the results are the same. that's not a band aid its a cure.

bbaudi382

but in a proper install there will be NO ground noise. a ground loop isolator is NOT a cure for the problem, it is a band-aid that hides the problem, but underneath the band-aid there is still a poor quality install that should be fixed for OPTIMAL performance.

dkelly

at both Alpine and Rockford tech support. we all agreed that the differences in signal using a good quality gli could not be heard. I talked with David Navone (autosound 2000) because i wanted to be sure. he agrees as well. everyone i talked with said they use them when needed and that using one did not reflect on the quality of the installation. if i'm being a jerk about this i apologize

bbaudi382

and you probably WONT hear a difference in sound quality.

however, in an installation where everything shares a common ground, there will be no alt whine or static cased by a ground loop. to me, that implies improper installation because you are spending money(albeit not that much) to fix a problem that shouldnt exist in the first place.