Question about Cary 308T CD player

I've been using a Cary 308T directly into 3 different units: an Audion Silver Night 7-watt 300B integrated amp, an Audio Research D-115 mk II 100-watt tube amp, and an Advent 350 50-watt receiver. In all cases, even with the Cary's analog volume control set to its maximum setting of 64, I have to turn the volume on the Audion and Advent to 2-3 o'clock for any real volume, and with the Audio Research amp, the only usable settings on the Cary are from 55-64; nothing below is even audible, which is a rather narrow range. My technician friend is perplexed because the Cary supposedly has enough voltage (3.6 volts, according to their website) to drive these units. Can anyone explain this? My speakers are 88 db efficiency; using an Art Audio Vinyl One with these same units works fine, but not the Cary. (This is the second 308T I've tried this with; both gave the same poor results.) Thanks.