A headphone amplifier - for what?

Prices for headphone amplifier start at EUR 20 on the upwardly open price scale. Often, the built-in amplifier and receiver headphone amplifier does not sound especially. My new hi-fi system no longer even has a headphone output. I recently reactivated a very good sounding old CD player in my bedroom. The built-in headphone output there sounds quite well. With the Head of the sound box but will be improved a bit. The spatial impression is greater, the bass and treble precise playing music more dynamic. For the price, the Head Box is processed excellently: a sturdy metal housing, a good current volume control and gold-plated RCA input jacks. The power is supplied via the included AC adapter. Connection to the amplifier or CD player via the Tape Out or Line Out jacks. I use the Head Box with Sennheiser HD 560 headphones and a Sony CDP 228 ESD.