Theta Audio DAC will not play on Onkyo Receiver


My Krell Pre-Amp and Amp were stolen so for the short term I have to play my Theta Audio equipment through my Onkyo receiver. Is there a way to convert the Class A pre-amp levels to something the Onkyo receiver will accept?
bhowland72
The Theta DAC should be outputting the standard redbook 2v, or no more than 3v I would say. Any line level input on the Onkyo should be fine. Is the level too high or too low?

Oz