Using headphone output from an intergrated amp

For a solid state amp or solid state integrated amp it is fine to have only the headphones in use. For the vast majority of audio products that have a headphone jack, the output to the amplifier portion is 'disconnected/cut off' when the headphone is inserted into the headphone jack.
You should have zero problems, and no danger using your integrated amp with only headphones.. (as long as it is not a tube power amp, or an integrated amp with a tubed amplification section.)
(if the integrated has a tube or tubes in only the preamp section, and all solid state in the power amp portion, then you can just use the headphones, and it is OK with no load on the part for speakers)
The only way it would be a probleem is if you had tubes in the main amplifier portion of the integrated amp.
Good luck!
(I use headphones a lot late at night.)

I agree about SS integrateds. However, most integrated amps have poor to mediocre headphone amp sections. Some of them are ok. If you are really into headphones, I strongly suggest picking up even a cheap used dedicated headphone amp. Of course, depending on how hard your phones are to drive, your results will vary greatly. You can pick up a new Creek starting at $199, or a used MF V-Can, and many others. I hear great things about Woo and Audio-GD. I commend you to check out head-fi.org, both for recommendations and used gear.

Thank you,guys. Mateored's answer leads me to another question I have that's dedicated HP amp VS intergrated amp HP section.

I have the modest Pioneer Elite A 35R and the Rotel RA 1062 and so far I am okay with the SQ. My HP are the Senn. HD280 pro, Audio Tech. ATH A700 and both are closed HP. I will be receiving the Senn HD 595 from Amazon in a couple days. The HD 650 is much better as I read but I want to take time to test the water.

I have been into headphones for many years and owned many different headphones and dedicated headphone amps. I also happen to own the Pioneer A35R and the Senn 280 Pro's.

The headphone out on the Pioneer is dreadful. You may not think so, but if you've ever heard a decent HP amp, you would. The Senn 280's are not difficult to drive, but have a limited upside as to what they can deliver.

I would suggest you pick up a used Senn 580 or 600, and a modest tube amp, such as a Little Dot or Antique Sound Lab to get a taste of what headphone listening can really offer. To learn more, check out Head-fi.org. And... sorry about your wallet.

Davetherave is so right.

Headphone amps make a huge difference- and I've owned at least 20, both tube and Solid State. I was convinced it was tubes only for me after much experimentation, then I met the Burson HA-160, which I own now. I'm just intoxicated with the Burson and music is even more pleasurable than before.

But you don't have to lay down the coin for a Burson or better- The amps Dave mentioned are really good for little money, and you can find them used quite often.

Have fun!