cd plays without preamp

OK so I just get my new Cambridge Audio 640 cd player shipped, I hook it up to replace my old unit and turn on CD player listening to great music and realize I forgot to turn on my preamp , only the amp was on. meanwhile I was adjusting the volume and tone controls and they were working ALL with the preamp off. Can someone explain this to me. The equipment besides the CD is ST-70 triode/ pentode amp by Bob Latino, Dynaco Pat5 bifet preamp,(which will be replaced in a few days shipping with a Cary) and a pair of Klipsch (Crite) Cornwalls. The Cambridge by the way is a very nice sounding CD player for the modest system