Volume difficulty with Krell preamp / Adcom tuner

I attached an Adcom GTP-450 preamp/tuner to a Krell KAV-280P preamplifier. Using the Adcom tuner yields a very low volume...even at the Krell preamp's highest setting (the digital readout says 150). This occurs with all FM stations regardless of signal strength. In contrast the CD player produces acceptable volumes at around 50. Previously the Adcom was attached directly to the Cary amp without a volume issue, Does anyone know what is wrong? The previous preamp (Sonic Frontiers Line 1) was fine.

Equipment:
Preamplifier: Krell KAV280P (balanced connection to amp)
Amplifier: Cary V12R
Speakers: Martin Logan Vistas
CD Player: Cambridge 540A (single ended connection to preamp)
Tuner: Adcom GTP-450 (single ended connection to preamp)