I do not find the headphone amp in this player to be very good. I believe it is the stock op amp output originally from the Marantz. I don't think it is the tubed output. That said, I love my player. I have used the Bottlehead Crack and love it. The reviews are uniformly positive. You can make it yourself or pay them a small fee to make it for you. It is a fabulous sounding amp, especially with Sennheisers. I also use an OTL amp from Antique Sound Labs which is warm and sweet with my Senns. It will depend on the headphones you plan to use. Which ones? Those are the only amps I have used. You will find many opinions on amps both here and at Head-Fi.org
How is headphone amp in Ah Njoe Tjoeb cd 4000?
How is the built in headphone amp? Is it warm and tube like, or does it sound like a transistor amp? I live in a duplex, so I listen through headphones quite often. Thank you.