Hissing and crackling

sp@nky · 05-01-2008, 12:32 PM

I am having a problem similar to SteamFire with my audio setup... it's driving me nuts!

At all volumes I can hear a distinct hissing (white or pink noise - basically no structure to it - not alternator whine). Regardless of HU volume it's always at the same level. Increasing/decreassing AMP gains increase/decreases it. The Hissing stop completely when changing radio stations or CD tracks (no audio for HU).

At high volumes the audio starts crackling, just like a blown speaker. The sound volume (SPL) at which it happens is different, it depends upon AMP gain only, not HU volume setting. The higher the Amp gain th lover the HU volume needed to trigger it and vise versa.

Ok, for the set-up, I have to original Head Unit but replaced the crappy speakers and added some Amps. The amps are an Alpine F450 for the Pioneer 12" bass and a couple Alpine F250 for the other various kappa speakers (I've tried some Sonys amps with the same result).

other noteworthy tidbits, the HU and Amps are not on the same circuit and I've tried some impedance matching between HU and amps, without success.

Help please

Brock · 05-01-2008, 12:59 PM

almost sounds like a ground or phase issue...like in the old days if you set up one speaker with + and - hook ups one way but then reversed the speaker end on the other....sending + into - and vice versa...you would get that sound.
Doesnt sound like it is picking up engine interference...and unless you can pinpoint some other accessory as influencing it....I would go back to installation...even a bad wire with a break in middle somewhere might cause distortion. Usually I have had it with bad contacts in amp...or on speaker.

Since you changed speakers I would check:

1-ground
2-ensure the + and - on radio are going into right spot on speaker end
3- make sure ohms are right....if it is 8ohm system and you are running 4ohms you will have issues sometimes.
5- ensure your connections are fully seated and tight especially from head unit to amps.

sp@nky · 05-01-2008, 01:53 PM

Well I did check and redo the wiring at least 4 or 5 times. What bugs me is if it was a ground loop why does the changing of station make the hissing quit?

Brock · 05-01-2008, 03:03 PM

could your head unit be bad and a loose solder on the board be causing it....if not too much a pain in ass you could remove HU and put a buddies in or the old HU...and see if you get same hissing....other than that I dont now. Does not seem to be volume related...
did not say if itwas same for radio as well as CD music...or I did not remember reading if there was a difference.
If constant.....are amps running parallel or inline? Could wiring harness going back to 400w AC plug in rear be putting off enough juice to cause interference?

Only thing I can think of ....and it is a PIA....is slowly swap out every thing one piece at a time and see if anything stops it....I usually start by swapping wires....with one length of new wire...first one speaker then the next...or amp wires...same thing. Disconnect one amp then the other ...swap their locations... check for loose tiny metal BB or other item that is just barely touching and given right harmonics buzzes...cant help on hisses...LOL. Usually grounds and loose connectors are popping and static.....hissing is outside interference and static.

I wish you luck and damn glad I am not one having to figure this out as it is something that is going to bug you to death until you find it.

**BPSFJ** · 05-01-2008, 04:07 PM

Sometimes a bad soldier joint at the RCA input/ output can cause this. But this sounds more like something in the HU because when you switch stations it goes away.

I know this may not be it, but GSM/ Nextel phones can cause this as well if they are constantly pinging for data. Does not sound like what you are describing.

Briman42487 · 05-01-2008, 10:04 PM

well if you have noise, the most common thing is noise in the recording. if it stops between tracks, that is what i would suggest. it may also be coming from the head unit. i would try to set your volume and gains correctly.

as far as the crackling, is it clipping or distortion? also, check your grounds. make sure your ground is on the sheet metal with a sheet metal screw or bolt through the floor. under a seat bracket or something like that is a terrible ground. also, make sure the paint is removed under the grounding location with sand paper or something like that.