phono preamp break-in machine

Tfkaudio: The disc being played doesn't change the output voltage of the CD player

Of course it does. The output voltage changes continuously in proportion to the instantaneous amplitude of the music, or in this case the test tones. If the tones are very low in level, the output voltage will be also.

That said, I strongly second Elizabeth's comments.

Regards,
-- Al

Why risk anything? Can't a preamp burn itself in properly by itself over time, or do these "burn in devices" condition the preamp in a certain way? Personally, I have to believe that any reputable designer would have tested the prototypes after they were broken in and then made adjustments so that the production models ran properly.
If I were going to invest in anything, I would invest in a variac transformer. I'd use it to gradually condition the equipment to full voltage. Things would probably last longer too.

I called Granite audio today. Don Hoglund who invented th burn-in cd said the break-in cd signal was mastered to mimic a vinyl record and is stepped -down between 45-60dbs so it is not overloading the phono preamp. The Granite break-in cd has been in use for ten years and Don said there has been no problems with it. The signal has been tested and verified to mimic the same output as a vinyl record. And like the cable cooker the disc can be use to "refresh" the circuts in the preamp. The signal output from the cd is full band width. Just passing on info and you guys "choose your poison". Thanks Ron