Headphone amp RCA output quality as preamp?

[Balle Clorin]

Many headphone amplifiers has both headphone output and RCA outputs .
How are the outpouts connected inside the box ? Can I assume they are from the same opamp and RCA output performance into a amplifier be comparable with the headphone teste loads presented the measurement section here?
I am considering to buy Lindemann’s Limetree Network player. An all in one streamer dac headphone and preamp. It uses AK4452 DACs and OPA1622 opamp for the headphone. But does that same opamp also drive the RCA? What are the consequences on performance?
I have also bought JDS Atom head amp , so I can choose to run my headphones from the Limetree Network unit headphone output , or run Limetree RCA to Atom, to headphones. (Hifiman Sundara, Beyerdynamic DT1990,Shure 1540,Grado SR125)
Limetree specs attached

 

[Balle Clorin]

More data

 

[Veri]

I have also bought JDS Atom head amp , so I can choose to run my headphones from the Limetree Network unit headphone output , or run Limetree RCA to Atom, to headphones. (Hifiman Sundara, Beyerdynamic DT1990,Shure 1540,Grado SR125)

Just use RCA line out to Atom to headphones. That is the whole point of the line output, and the recommended way to do it

 

[Balle Clorin]

But is can a headphone opamp be suitable as line out driver also? Or should a different opamp be used for the line out..

 

[GGroch]

Veri is correct.
In looking through your posted specs, and the Linedemann website, it is clear the Limetree network player is primarily a Network Player designed for connection to an amplifier. The headphone jack on the front is added for convenience, and probably sounds OK with most headphones.

The OPA1622 was designed to power headphones and is almost certainly not in the Limetree Network's preamp out circuit.

The Limetree Network Player's specifications for its headphone output provides none of the information you need to tell for sure. For example, no headphone output impedance is quoted that I could find. Your first posted specification sheet shows a 100mW output for 33 ohms, which is probably OK for low impedance phones, but your DT1990s are 250 ohms and the Limetree will put out a lot less to that. Compare this to the 1100mW output of the JDS Labs into 33 Ohms, and 250mW into 300 ohms.

The Atom is essentially perfect as a headphone amp. There is no reason not to use it. Veri is correct.