The Phono input is dealing with extremely small signals ranging from a few hundred microvolts to a few hundred millivolts. Although this input is extremely well protected, it is sensitive to its environment. Make sure your Devialet has been upgraded to the very latest firmware and that all its inputs are well configured. This is especially valid for the AIR input which must be locked to a WiFi network or de-activated otherwise it will keep sending very strong scanning bursts that may disturb such a sensitive input such as the Phono input.
Note that the noise floor on the Phono input is higher than on other inputs.