My friend own a ARC ref 75se for many years and doesn't experience any hum/buzzing noise from its transformer.
Transformer hum/buzzing could be due to DC offset in AC mains, or the transformer loosen itself from the chassis, both can be easily fixed. But if the transformer hum/buzzing due to the transformer core adhesive starts to break apart and the laminated layers separate from each other slightly, the vibration of these layers is the cause of the humming noise, once the adhesive starts to break, the noise will gets louder over time and need to be replaced with a new transformer eventually.
my suggestion is bring it home for audition, if it still buzzing return it to the seller.
