what length Interconnects are you using? Passive dictate the use of short [2 meter] or less length interconnects.
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The CAL is a tube DAC? If that is the case, then 5.5K is probably way too low. I have heard that tube output stages commonly require more like 50K or even 100K impedance on the passive. I have run into this myself when using a 25K passive with a CJ dac: the sound lacked bass, and generally sounded small and compressed. When I changed the (very expensive) passive to a cheap home made one that was 50K, there was a huge sound improvement.
Hope this helps. Passive preamps are a real bear to get working sometimes.
It definitely sounds like an impedance mismatch issue. A DAC outputting in the 3V range should easily be able to drive an amp with half the sensitivity (1.4V) well into clipping. If you do not hear major distortion when your volume is cranked wide open then the amp is apparently signal starved. Try another line source component, borrow one from a friend if possible (tuner, cassette, or another CD player) & test again. If that doesn't help then you need a better passive pre or maybe even an active one to get the required gain. I'll email you privately with details on a rare unit that is presently available.