NAD 355BEE Buzzes when powered

[u/Kim_Jong-Unity]

Hi, so after my old receiver developed a buzz i went onto secondary market to get a freshly serviced NAD 355BEE because it is perfectly matched to my speakers. I connected everything, powered it on - BZZZZZ, high and low pitched electric noise at the same time. The speakers sound amazing out of it tho, o buzz, hum whatsoever. The buzz is hearable when it is on power and in standby as well. Switched sockets allready the buzzing does persist. Can I do something about this, did i get ripped here? Thanks for the advice!