You should check the spec on both player's output. Most are 2~2.5 V RMS through RCA and > 3.5 V RMS through XLR. Some do only 2~2.5 V RMS even through XLR.
Maybe the Rotel had significantly more VRMS than the Grant Fidelity? Were you using XLR or RCA through the Rotel? That also matters.
Maybe the Rotel had significantly more VRMS than the Grant Fidelity? Were you using XLR or RCA through the Rotel? That also matters.