so it could be something introduced by whatever audio setup thats used by hildon-desktop?

or could it simply be that replacement desktops dont bother with switching the audio hardware off when its not in use?

I reckon there are 2 types of hiss and one of them is only audible in the N800.

1. As I described in the first post of this thread is the N800 produces a very hissy sound when connected to my car radio. It's a really ugly, dirty hiss. It must be something to do with the radio chip with the jack-jack cable possibly acting as an aerial because like I said before:
"When I click the 'play' button on the radio applet I can hear the background hiss and the radio station and after 2 seconds the hiss goes away leaving me with clear radio sound. "
I can only hear this type of hiss in my car, well, I could since I can't be bothered to listen to music with so much hiss

2. The other one is not so obtrusive. It's probably not audible to everyone, it's definitely not a loud hiss. This is the one that you can hear when the sound chip is working and about 2 seconds after a sound has finished playing and this hissing sound finishes with a click.
They might have improved it a bit because the N800 produces slightly louder hiss. I,for one, can barely hear it in the N810. This is the one you have been talking about here.

the ting is that 1 can be related to 2, unless you get 1 with "touch screen sounds" set to off.

now im tempted to investigate what player hildon-desktop uses for its system sounds...

I don't think they're related. I get 1 no matter if screen sounds are on or off

ok, and some quick testing here confirmed to me that 2 is hardware related. youamp and mplayer produced the same hiss as the system sounds, with system sounds off.

still somewhat odd that issue 1 is for two seconds rather then the whole time the sounds are playing (as i would have expected, not that im an expert on audio cabling) if it was related to the plug and so on...

I use a 3rd party clone of a Belkin FM transmitter, and I get a bad hiss on the car radio - the hiss volume is constant no matter what I set the media player vol or master vol to, so I end up running media player's and master's volume at max, which tends to produce distortion.
I tend to listen to speech recordings (catch-up comedies from bbc radio4 for example) so the hiss isn't a big problem, but it does spoil it for music.
I don't remember the hiss being there with headphones.

perhaps the relatively low impedance of the headphones sinks the noise signal, but the relatively high impedance of an FM tx or auxiliary jack on a sound system allows the noise level to float quite high?

does anyone have some stereo jacks and sockets, croc-clip leads and 50 ohm resistors to make a "break-out" box and try adding/removing the resistors when connected to the line or aux-input of some active speakers?

^There ya go... now we gettin' si-yun-tiffic!

But I think that may be what is needed.

The Nokia supplied earbuds for me, are clear as a bell with no hiss. But then again they do have a mic. Perhaps a "dummy" load is needed on the mic side when connecting to other speakers.

https://bugs.maemo.org/show_bug.cgi?id=1040

-T.

I dug out some low-impedance headphones - some respectable Sennheiser ones I've had for a long time which are quite efficient (very loud at low power levels) - and there was only a tiny background hiss and the sound quality was excellent (Lord Of The Rings sound tracks which has very wide dynamic range).

I've found a 3.5mm jack extension cable and some croc-clips and resistors, so I'll try my crude hack suggested above and report back.

Hmm. I find that the hiss is much more prominent with my Sennheiser CX300s than with anything else. I've had a few pairs of them (nothing beats their bass on the tablet), so I can see that it seems to be just with these earphones. What pair do you use?