Wadia 27i DAC into Shindo Masseto pre-amp

The Wadia 27i decoder contains user-adjustable switches to vary its output voltage, a feature especially useful when feeding straight into my VAC amp. But soon I'm going to introduce the Shindo Masseto preamp between the two and am wondering how much voltage I should send to the preamp, i.e., is there a safe limit on the level of signal voltage I input to its line stage ?