Stereo Problems Please Any Suggestion Will Help

[unarmed_skyline]

ey,

I'm having problems please help,

Ok pretty much i'm running two amp's, one under the front passenger seat and one in the boot compartment next to where the battery is. The amp in the boot is a 4 chanel running front splits and my sub and the front amp is running my rear speakers, dont ask why its wired like that due to distrubiting power to best matching speekers, anyways it was all runinng fine no problems no nothing, except i was haveing my rear amp cut out when the volume was turnned up not even half way, as if it were overheating although it wasnt hot at all and it would do it even when i started the car up after leaving it overnight or longer, anywayz i figured out that the amp was brigged for the sub in the first and second chanel and the front splits were on chanel 3 &4, anywayz i realised that with this amp to run it brigged effectivly 3 chanels you have to run the brigged unit my sub in chanel 3 & 4 i swapped that over and it fixed the problem but now i have an increddibly unbearable ground loop hum or something, and it isnt just threw the rear amp it run's threw both amp's, i have cheaked all my grounding's and all are grounded perfectly, none of my power wires or ground wires run anywhere neer and speaker or rca wires, i havent been able to isolate the problem any help would be greatly appretiated,

[RANDY]

What happens if you don't bridge your sub? My 4-chan amp required me to use positive from channel 1, and negative from channel 3. If it goes away when you unplug or unbridge your sub, it might help narrow down the problem.

Are you running power right off the battery, or off an existing circuit? Where are you running your ground to for both the amps?

[Dose Pipe Sutututu]

I would check your earthing connection..

Run both amps off the same earth point to eliminate any ground loop noise..

And see if your power cabling is sufficient.. in your case I would recommend at least a 8ga power cable, if not 4ga into 8ga

and check if your amp's bridged impedence acceptance matches the sub

4ohm -> 4ohm or 2ohm if your using a DVC sub

[unarmed_skyline]

the rear amp is being earthed straight to the chassie where the battery earths to the chassie, all 12 sorces run straight from the battery and not threw existing sorces, the front amp is earthed stright to the chassie there is never any power or ground wire longer than 30 cm and none of them run anywhere neer the rca, i have tryed not bridging the amp and that doesnt seem to work, the wired thing was that i had no problems or trounbles with either amp untill i switch the channels on one amp and the problem has spred to both amp's without any wirering changes, im running 8 gauge wire which in 90% of purposes if sufficent never had any problem in any other system ive set up like this, not sure bout the ohmic impedence ill have to cheak that out tommorow DVC sub?? not sure what that means

[RANDY]

Dual Voice Coil. Lower impedance I beleive?

I kinda wanted to say that it sounds like a ground is not working properly, or that power is not sufficient into one of the amps.

Perhaps you could try un-powering one of the amps altogether to see if the problem still occurs with just one?

[unarmed_skyline]

The problem still occurs when i turn one of the amp's off, i've been fiddiling a fair bit trying to figure it out and nothin seems to be working although we now think that somehow i am getting interferince entering most likly the grond loop but possibly the +12V line, the hum seem's to be not only a turbo sounding hum but there is also a rusty purr as well, most likly it is entering before the headunit as it is coming threw both amp's although i have cheaked all my grounding and power points and they all seem fine, its not a dvc sub and the impediance's and ohom's are all matched, i can also hear my inticators threw the speakers when the car is on accessory, hooking up an ossilloscope (i cant spell) tommorow to try and find out if there is noise on the line and if so which line hopefully this will fix the problem,

[Chris Rogers]

could also be a damaged headunit- have had it in several vehicles I have reworked.

[RANDY]

So... the remote wire from the HU... is that getting split into two to trigger both amps?

Like Chris says, and you beleive, it could be the HU if one amp on its own will still have the effect. How well grounded is the HU? I ran the grounding cable to one of the screws that hold the frame of the manual shifter into the body. (ran wire through cigarette lighter wiring loom)

[unarmed_skyline]

yeh i grounded it to that same point, gearbox surround, the headunit is only 3-4 months old so its most likely not the head unit but if i cant diagnose the prob by the end of the week ill get someone to check it out, the remote wire goes straight from the head unit to the first amp then to the second connected both together at the front amp trigger plug

[RANDY]

Well... i'm out of ideas sorry. The only other thing that i'd want to try is to hook up (any old) car speaker directly to the HU and see if it has issues too. I beleive there's something like 2 Volts going out your RCA's, so if they have sprung a cut in the shielding then perhaps it's grounding on the car body somewhere?

That test would rule that out, but either way man... let us know what you find when the issue is resolved! =-]

[Chris Rogers]

randy,

closr to what I was going to say. I would swap units if you have a similar one handy. all it would take is a bad earth on the amp side of things to pop the RCA shields and introduce noise into the system.

try swapping units.

actaully do this:

radio on, unplug RCA cables. - noise? yes - amp issue ( earth or ground loop) no radio problem be it earth or burnt traces on the board.

[unarmed_skyline]

i finialy fixed it, for some reason the rca wasnt grounding properly, so to fix this i ran a wire from the rca sheild to ground right next to the head unit,n the problem was fixed, really simple grrrr waste of 5 days, although i still have no clue what happen that the rca wasnt getting grounded the hum's have gone now, i think mabye the gound wire got burnt out neer the headunit but i have no way to prove that without dismantiling the head unit which im not about to do to a $1600 head unit, its working now and thats good enough for me, thanks heaps for all your help

[RANDY]

I could see you heading that way, Chris =-]

The only reason I didn't suggest changing the HU is because all the speakers are being driven by the two amps, so unplugging the RCA would just kill all the speakers... unless the HU has two pairs of RCA outs? =-]

Glad to hear you got it sorted!

[unarmed_skyline]

headunit actully has 3 rca outs, but yeh havent had any probs with it now soo all sorted thanks for everyones help