Headphone Output for Preamp Out.....

I have a integrated amp with no preamp out. How close does the headphone output come to being able to drive a tube amp with an input impedance of either 116Kohm rca or 270Kohm xlr (1KHz)? Out in left field or a possibility?
Converting to XLR can be a problem. Different impedance. I've tried adaptors but they all produce a lot of noise and reduce the volume.
The big issue you will run into is you will get a high level of hiss. Other than that it will work fine.