I've tried Belles 150 both versions (including hotrod)when I was waiting for my new amp from dealer. I couldn't listen to even cozy music for more than one side of vinyl. Belles 150 has emphasized mid-highs and mid-base, doesn't realy have a dynamics as SS amp 150W/ch should have.
your amps' transformers can induce the parasite currents onto the components standing right above even on the different shelf especially on digital source. Try to find for your Heath amp other place rather placing it under preamp or source. If you have a possibility to turn your EQ off than it'll be extra help for internal element isolation.
Heath isn't the only exception. In that list you can add a bunch more even expancive ones.
So my first thing to do is to isolate power amp from any source or preamp component by at least 1/2'
The second would be to go with no EQ.
your amps' transformers can induce the parasite currents onto the components standing right above even on the different shelf especially on digital source. Try to find for your Heath amp other place rather placing it under preamp or source. If you have a possibility to turn your EQ off than it'll be extra help for internal element isolation.
Heath isn't the only exception. In that list you can add a bunch more even expancive ones.
So my first thing to do is to isolate power amp from any source or preamp component by at least 1/2'
The second would be to go with no EQ.