maemo.org - Talk - View Single Post - Audio, PA, XPROT, and the damage done

	electroaudio	2013-09-10 , 15:53
	Posts: 381 \| Thanked: 336 times \| Joined on Jan 2011 @ Stockholm, Sweden	#2

Originally Posted by joerg_rw

Though all this might be needed and maybe even OK for the built in speakers

Well for the built in speakers then it is good to have it all there to allow for maximum output.
-I dont think that the way internal speakers are used is so demanding on quality.

it's probably worth it to review and rework the sw-side audio chain when using headset connector, particularly when using it for 0dB line-out to any home-stereo or even professional equipment. Alas it's not possible to auto-detect whether headphones or a 3.5mm->2*cinch Line-In cable is connected, so any such adjustment has to happen by triggering it from a sort of GUI.

I dont believe that headphones need any protection from the n900.
Headphones usually are capable to handle outputs from soundcards and are most likely designed to withstand other strong sources without breaking.

For first experiments it might be worth it to completely shut down PulseAudio and use the plain ALSA for audio output. CAVEAT: this scenario is known to potentially blow your speakers in N900.

PS: I don't think the class-D amp by itself is that bad.
Cheers
jOERG

This would be very interesting to try on the headphones output

But i was also thinking about if not speakerprotection could be made of passive electronics (a large cap in series with the speaker) or as d&b amplifiers which only uses gainreduction as speakerprotection but which has a sophisticated way to measure the temeraturedependant impedance of the speaker and to predict the movement of the cone. ( is conemovement, Xmech, even a problem here?) otherwise a amp with a very high outputimpedance (currentamp) could be used and a simple mathematical formula for the induced and transferred heat in the coil could be utilized in the digital world.

__________________
Deskypplet , a desktop for N900 *RIP*

Last edited by electroaudio; 2013-09-10 at 16:07.

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