DC blockers - what's your experience

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.

Power is primarily clean here where I live do have an LessLoss 640x on my LessLoss DAC and audiolab dc blockers on my digital and analog FEU. More for assurance than anything else. Amps are right into the wall.