Low level noise from RCA's

[suprabrown]

ey up peeps,

I've just powered up my install, new JBL speakers front & rear plus amp in the boot to drive the speakers.

I'm using the line out RCA's on the headunit to feed into the amplifier, the only problem is that there is a constant background 'noise' or 'hiss' from all speakers, any idea where this could be coming from? Even in between say CD tracks when all should be silent there is a hiss from all speakers, as though the volume is cranked right up.

I've tried runnning the ground for the amp from both the chassis (good local point) and directly from the battery without making a difference....

any ideas would be appreciated,

cheers
maark

[DanStwo]

Its hard to diagnose as even the best systems have background noise...

In the main I have found it to be the gain on the amp adjusted to high... how have you matched the gains on the amp with the headunit?

What headunit and amp do you have?

Could also be the earth for the headunit, but that would be unlikely I would have thought, still its worth checking

HTH
Dan

[suprabrown]

Hi Dan,

I did think about the earth on the headunit, I didn't have time last night to take the dash apart and run a test cable in, it is deff on my list of things to try.

I don't think it's the gain on the amp cus they are still turned right down. I only got the power on late last night and I didn't think the neighbours would appreciate my taste in music :)

I will be setting the gain later, I was going to turn the headunit to say 75% volume and then turn the amp gain up until I get some distortion on the speakers, then back the gain off slightly. I don't think I can adjust the gain on the headunit?

I've got a kenwood DDX8035 headunit and a JBL 1100W 6ch amp - GTO 6000 I think it's called.

cheers,
mark

[supra sam]

Have you run the rca's down the same side of the car/next to the power cable for the amp? I have known this to cause interference if the rca's don’t have great shielding, might be worth just taking them out and running them loose down the other side to see if this makes a difference. :)

[DanStwo]

It might be the Power/RCA issue... I have never personally encountered that issue but its one to remember...

Another thing and it might sound stupid but what music are you testing it with? It might be a rubbish quality CD?

Dan

[Kevin M]

In the main I have found it to be the gain on the amp adjusted to high... how have you matched the gains on the amp with the headunit?
Dan

:yeahthat: Chech through the menus in your head unit mate. Often the pre-outs have their own setting for gain, usually in a menu headed: Sub out, Rear, etc.
Sounds very much like the gain on the head unit is either off or almost right down in the settings, hence why youre getting the hissing sound.

Also with regards to the rca wiring routing, being near the power cables:
Have you tried the car running with the ice on? And if so, does the background noise change?:search:
Past experience, i have found that this usually only gives you a whining noise that rises and falls in unison with the engine revs.( Think it comes from the alternator).
You dont usually get a hissing noise from that issue.
Good luck!:d

[suprabrown]

I did consider the routing of the RCA's, I have taken them under the arm rest, under the carpet, then under the back seat, so they should be well away from any power cables.
I'm not getting the usual 'whine' that is caused when the engine is running, the hiss I get is there with the engine on and off :( more like the volume being fully up and nothing playing.
I have tested the unit with, CD's, DVD's, Ipod interface and the radio, still the same, so I don't think it's the music. The noise is there all the time even without anything playing.
you guys could be right with the head unit gains though, the unit I have is pretty trick with a 5.1 DSP built in, so I wouldn't be suprised to find other settings......................way to complicated for a numpty like me, what happend to the old bass and trebble knobs???? <VBG>
I'll let you know what I find,
thanks for the info..............

[@lpher]

What brand headunit and amp are you using?

[EncoreWRC]

Are you running the RCA's next to the power or earth leads?

That will very often cause a problem. Also if you have run them along seperate sides of the car how have you earthed your amps? Any buzz noise, always check your amps earth first. Make sure it make the best possible contact with the body..

Make sure live and earth cables are not intwined at all, and if you are running more than one earth to the same earth point on the car think about running 2 earths into a distrubution block and then one earth to the body...

I have 6 years of big ICE installations and found that these points normally sort out most interference problems.

If its alternator interference it may be head unit end - secret is to run a big battery earth from the alternator to the body..

Sorry for the long post but trying to throw as many ideas at you to try as poss....

[suprabrown]

i've got a kenwood DDX8035 headunit (the double din unit with the 5.1ch. DSP built in) and I'm connecting this to a JBL GTO 6000 amp.

I tested all earth connections yeaterday by connecting to a 6mm cable both to the battery and to a good chassis point - no difference was made by either connection, so I'm assuning this is not the issue.

so then I started to look at the gain setting on the amp. The instructions that came with the amp suggeted you turn the headunit to 3/4 vol and then up the gain until the sound starts to distort, then back off a little. That's how I set it up. However.............. all I did yesterday was to turn the gain down until the hiss went away and all appears to be well.

so it looks like a school boy error of having the amp gain set to high, even though I followed the instructions!

does this sound right to you guys that know about this sort of stuff?

next I'm going to play with the time alignment :)

cheers
mark

[@lpher]

does this sound right to you guys that know about this sort of stuff?

Yepp :)


next I'm going to play with the time alignment :)


Youre in for a treat :D