Looks like a very poor design.
Signal input just by the power IC?
Speaker output on the opposite side of the board?
What were they thinking?
As of input sensitivity: gain is 20X so some 800mV at which point it will put out 15W into 8 ohms, more than enough to NUKE any headphone plugged here.
Even 32 ohm headphones will get some 4W RMS, same result.
So use as is, adding 25k Log/Audio stereo pot at input, start with volume on 0 and raise it only as needed for listening.
Side note: China is SO favoured commercially , shipping is so much helped, that anybody designs and manufactures anything, no matter how poor design is, and is guaranteed to sell.
Oh well.
Signal input just by the power IC?
Speaker output on the opposite side of the board?
What were they thinking?
As of input sensitivity: gain is 20X so some 800mV at which point it will put out 15W into 8 ohms, more than enough to NUKE any headphone plugged here.
Even 32 ohm headphones will get some 4W RMS, same result.
So use as is, adding 25k Log/Audio stereo pot at input, start with volume on 0 and raise it only as needed for listening.
Side note: China is SO favoured commercially , shipping is so much helped, that anybody designs and manufactures anything, no matter how poor design is, and is guaranteed to sell.
Oh well.
