check all your grounds, a hiss can indicate feedback from a bad earth,
otherwise you can try a ground loop modulator, i use one im my camper where
i run a 10 disc changer, didgital tv along with an xbox... it reduced the
problem significantly, another way cn be to upgrade speaker wire to oxygen
free, i use vibe flat gives me the best results engine on or off
"Gazz" wrote in message
...
I've got a motorhome, and i've just got a dvd head unit, it's one of those
cheapo chinese ones (arkon) but the price was right for what i wanted,

One annoyance, when ever the volume is turned on (i.e. off mute) i get a
loud hiss in the speakers, this happens on all modes, dvd/cd playback,
radio, aux in.

even with nothing connected to the unit except power and the speakers, i
get the hiss, so it's not anything i've connected to it (which is only the
audio from the sky box)

I can make the hiss louder by turning up the trebble (think it's called
that on this unit, other one to bass makes no differance if i have the
loud function on or off, it has 3 preset equalisor settings, and the hiss
changes in volume slightly when they are cycled through.

I guess this wouldent be a problem in the standard car setup where you
need the volume up loud to overcome the engine noise, road noise etc, but
in the motorhome especialy at night ,we can easily hear the sound with the
volume on level 2, and of course the hiss is almost louder than the sound
then.

Is there such a thing as a hiss reduction unit?? i'm using the unit's
internal amp, and want to keep it like that, that's why i bought a dvd
head unit in the first place, the speakers in the TV are at the back and
are tiny, and were far too quiet due to the TV being built into a cabinet,
so the dvd head unit got me the amplified speakers on the front i wanted,
but now i have this damn hissing.

I have tried different power supplies, the unit has it's own circuit
directly off the batteries, i tried it off the TV's regulator which
ensures exactly 12.8 volts gets out no matter what the input voltage is,
and removes all spikes, ripples and hash on the incoming power, still got
the hiss.

Anyone got any suggestions to how i can reduce this hiss, i can get it
bearable by turning the trebble right down to minus 8, but then the sound
is weird as you'd expect.