ARC ls 25 mkii cd/dac input too hot?

I have an Audio Research ls25 mk2 preamp and pass x250.5 amplifier. I have a Bryston bda-1 dac and Acurus acd11 CD player. When I listen to CDs and the recorded music gets louder, it sounds like the signal going into the preamp gets too hot creating a little distortion. I’ve tried a few different CD players, both connected directly to the preamp, as well as using them as transports through the dac. Both created the same issue. I don’t think I’ve noticed it when using the iMac as a source for the dac.... I’ll have to check that again.
I’ve had no problems when listening to records. The signal is definitely lower.

It seems like the output of the digital sources is too loud for the preamp. Does that make sense?
Have you tried adjusting the gain on your preamp? There are 3 different settings per input.
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Andirocks, yes. I have them at the lowest setting.