I made the mistake of buying a "Digital Optical Coaxial to Analog RCA L/R Audio Converter + AU Power Adapter" from [email protected] via ebay. The supplied product caused major damage to my vintage audio equipment.
The product was either simply faulty or a deliberate piece of junk pretending to be a DAC as advertised.
Despite contacting ebay they were their usual incompetent self: no help at all.