Headphone to line level inout

In my case I have an HP TX1000 and I am connecting the headphone out to the line in of an SRPP vacuum tube preamp. The headphone out level is much too high to connect directly. I was getting quite a lot of hiss and interference even with the computer volume completely off. I found this site and after many, many, I repeat many trials, and this works the best for me: I used a T-pad.

http://www.nu9n.com/tpad-calculator.html

I ended up needing 35db of attention calculated with 600 ohm input and output impedance. The resistors I had available to use were 560 ohm for R1 & R3, and 22 ohm for R2. It's still a little hot but I can compensate with the output level control of the computer. I tried 680 ohm for R1 & R3, leaving R2 as 22 ohm, but it seemed like there was just not quite enough level to fully realize the potential of my preamp. My best guess is that 580 - 600 ohms would be ideal for my application. This got rid of the hiss and noise problem.