DC blockers - what's your experience

DC causes my amps toroidal transformer to buzz fairly loudly. The only time it happens is when my wife uses this one particular space heater.

I think DC on an AC circuit in the US is very rare and is often blamed for buzz when it is something else.  

Your audio should be on dedicated 20-30 amp lines 

and I had  had awg 10 copper wire and to make more quiet my audio electrician friend installed 4 wire 1 common ground ,the other a separate is plated ground 

Going to its own small buzz bar  it sounds dead quiet day or night .

I use iFi on my NAS and fiber transmitter….they work excellent and are extremely affordable. 

I had major problem with transformer hum that lasted for years, this along with over voltage issue(124-126v). Never could get rid of transformer hum, bucking transformer for the over voltage. Suddenly one day I come home no more transformer hum, voltage down to 119-121v, this has remained for years now. Seems electrical grid was finally repaired.