Headphone output straight to amplifier input?

[ajblanco09]

Hello.
So, a friend of mine had this bluetooth headphones that had one of the drivers broken, so he gave them to me. I was planning to hook them up to a test amp I have, but I don't know if I can just connect the output that goes to the headphones to the input of the amplifier, does it affect in any way the little built-in amp of the headphones?

The headphones brand/model is Mpow/Swift and the amp is a bridged tda 2005

[rhb]

Find out the impedance of the output and the input,  Make a resistive pad so that the two match.  I'd expect that you need a smallish resistor across the headphone output and a larger resistor in series with the amp input.  An aux input will probably work fine this way.  The headphone output probably won't have enough output to drive  a power amplifier external preamp input.

Most "line in/aux" inputs are around 30-50k.  If the headphone transducers are say 2k then you want a 2k resistor across the headphone amp output and  a 48k resistor in series with the amp input.  Strictly speaking, you should do the algebra so that the parallel combination of the headphone load and the series resistor and input impedance matches the headphone amp and vice versa.