How powerful the headphone amp on my integrated amp is?

[ChevyMonsenhor]

For about two years i lived in Porto Alegre and used an older NAD T773 a/v receiver for everything audio related. Near the place where i lived a dude had some great headphones, including a Victor HP-DX1000 that i absolutely loved, my old NAD didn't even sweat amplifying that thing.
When i moved back to Rio Pardo this year i received an offer i couldn't refuse on the NAD, like double the price i paid for it originally, so i sold it and decided i would seek something even older and japanese, for the hell of it and in that endeavor i ended up with a japanese market exclusive Onkyo Integra A-817XD from 1988.
It hasn't been serviced yet but that doesn't hold it from sounding decades better than the NAD, it has so much soundstage, perfect channel separation (i game with my headphones hooked to it) and that's not to mention the power on the speaker output.
One thing i don't know and i can't find find out about anywhere is how powerful the headphone amp on the front of it is, since the harder to drive headphone i have on hand is my JVC Ésnsy that even my iPhone has no trouble dealing with.
How could i find that out? Is there some sort of measurement i could do?

 

[Sonic Defender]

It will not be a separate amp, almost for sure. They simply put a bunch of resistors between the main amplifier output so you are running from the amp that drives the speakers, but obviously the power is attenuated. I do suspect that you could measure it, but the best method eludes me. Somebody else will likely offer you a few ideas. That is a nice Onkyo, my brother had a very similar model fully restored and it was a beautiful thing for sure.

 

[ChevyMonsenhor]

It will not be a separate amp, almost for sure. They simply put a bunch of resistors between the main amplifier output so you are running from the amp that drives the speakers, but obviously the power is attenuated. I do suspect that you could measure it, but the best method eludes me. Somebody else will likely offer you a few ideas. That is a nice Onkyo, my brother had a very similar model fully restored and it was a beautiful thing for sure.

That is interesting, could be either a really good attenuation or a rather weak one. It does get loud for sure on the headphone output, i couldn't listen to anything louder than 1/4 turn of the knob.
If i can actually measure it and i dont find a good result, i could pipe the signal that comes from my DAC (a Topping D10) through the amp's line out onto a separated headamp.