Need help connecting headph. amp to cdp or preamp

My current set-up inludes a Linn Genki, Kairn pre and LK140 power amp. When I connect my RA-1 headphone amp to the Genki's regular outputs I get bad distortion through my Sennheiser HD-580s. The distortion goes away when I use the variable outputs on the Genki (which I believe are designed to accommodate users who want to run the Genki through a power amp without a pre). The only problem with this is how low the volume gets, which leads me to suspect something's not quite right.

One suggestion I received was that the output voltage of the Genki might be overloading the RA-1, and that I might want to connect it to the tape out my preamp. Would this work? How would I avoid sound coming out of my speakers -- shut off the power amp?

I'd love to hear from anyone who has a similar set-up. In particular:

1. If you connect the headphone amp to the CDP, what outputs do you use?

2. Does it make any sense to connect the headphone amp to the preamp or to the power amp, or is that redundant. If you can do this, what's the best way to hook it all up?

Thanks.