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I noticed when driving headphones DT770 32 ohm directly from motherboard output vs buffering them there is large loss in volume compared to my HD6XX...
Why would this be?
The ALC887 audio chip in the mobo has a 2 ohm output impedance according to the datasheet, so the volume difference with 32 or 300ohm load should be negligible, but here they are so much louder when buffered that I can start to hear the hiss of the noise floor, while the HD6XX volume stay the roughly the same when buffered or not, as expected.
My only guess was that there could there be some sort of dynamic gain adjustment going on in the alc887 based on load impedance, since generally lower impedance will need less gain than high impedance headphones.
I didnt see anything like that in the datasheet, the output level is given as 1.2Vrms, it doesnt mention the load.
Why would this be?
The ALC887 audio chip in the mobo has a 2 ohm output impedance according to the datasheet, so the volume difference with 32 or 300ohm load should be negligible, but here they are so much louder when buffered that I can start to hear the hiss of the noise floor, while the HD6XX volume stay the roughly the same when buffered or not, as expected.
My only guess was that there could there be some sort of dynamic gain adjustment going on in the alc887 based on load impedance, since generally lower impedance will need less gain than high impedance headphones.
I didnt see anything like that in the datasheet, the output level is given as 1.2Vrms, it doesnt mention the load.
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