amp? constant hissing and general questions. please help

[nixesteve]

Hi i hae the 2001 exec 2.0hdi.
Iv installed an aftermarket headunit with flip out screen. I love it to bits only problem is thers a constant hissing with engine off or on even with volume down !
Anyone no what could be casuing this?

Iv heard the exec models come standard with an amp build it in the boot. If so could this be causing any problems? and if so where is this amp! the cd changer is gone from the boot but didnt no if the car had an amp or not.

help would be appreciated greatly!

Thanks
Steve

[mandelbug]

Hissing from amp's is usually when the gain is wound up too high. Although it might be worth putting a good earth cable in for the head unit to help.

EDIT - It could just be the circuit design in the after market head unit causing interference

[lozz]

Ive had this with other cars before when fitting an aftermarket head unit.
igot round this by cutting the original negative earth and earthing it elsewhere,

[nixesteve]

after alot of reading iv heard its something to do with line out n speaker lines etc. iv heard aftermarket headunits run at a different speaker level so this affects the amp and causes the hissing. if anyone can fill me in on this and help sort it i will be extemely greateful!!!!!!!!!!

thanks
steve

[Gary406]

hissing sounds are usually caused by earth problems..

ie the earth points are all on the same car causing them to loop each other making an interference

i use to get it wen i installed 2 amplifiers but now i dont get the tiniest of hiss's

i upgraded all audio leads to expensive ones and that stopped the interference

[Gary406]

ok, what head unit have you got

i once had a pioneer that did hissing even with engine off and sound tuurned to 0

it turned out the radio was crap altho it was brand new and it wasnt upto the job of running my system

[nixesteve]

headunit is a meos. expensive but worth it. that shudnt be the problem. Iv earthed it aswell. after ruling these out im left with the amp. A few people have mentioned this problem on here and they hav solved it with alot of wiring etc. but im no good with electrics at all, so wudnt even no wher to start

[Gary406]

you need to get the radio checked out mate

i know a fer bit about car audio and i have to say ive never ever heard of meos

iv just google'd it and it came up with a 7" double din radio with dvd
for £200

thats a lot of radio for £200 mate

if you want the same radio from sony, pioneer , kenwood your looking double that price

and alpine is about £700 so it might not be your JBL standard amp

[lozz]

you need to get the radio checked out mate

i know a fer bit about car audio and i have to say ive never ever heard of meos

iv just google'd it and it came up with a 7" double din radio with dvd
for £200

thats a lot of radio for £200 mate

if you want the same radio from sony, pioneer , kenwood your looking double that price

and alpine is about £700 so it might not be your JBL standard amp

ionce bought a double din dvd head unit it had all the toys it was an import ..ithink it was in the motor for a day it was an Absoulute pile of shite,
it costed me more for the postage than what the unit costed,
ihad Aford galaxy back then with limo glass so dvd systems where all the Rage .. what ilearnt was "You get what you pay for,

You can pick up all the Ching chong car dvd players at www.chinavasion.com for cheap but there best left alone,

[poddack]

I think there is a control signal from the radio to the amplifier, if this is permanently connected to 12v at the amp end it will stay switched on with the engine off. Also likely to flatten your battery.