I demoed the Prima Luna Evo 300 against four other tube integrated amps; see https://forum.audiogon.com/discussions/integrated-tube-amp-demo-follow-up. In comparison, I found the Evo 300 to be somewhat veiled, or "muffled", in its sound just as you have.
BTW, I have now moved on to a Pass Labs XA 30.8, with Conrad Johnson preamp, which is another giant step up in sound quality.
BTW, I have now moved on to a Pass Labs XA 30.8, with Conrad Johnson preamp, which is another giant step up in sound quality.