I picked up a NAD C298 which was still in warranty, to replace some Hypex NC500MP mono blocks (OEM & in Ghent Cases)
The c298 is exhibiting the same hum/buzz from the PSU. I popped into the SevenOaks where it was purchased and they tested another unit they had (both around 1306 serial number) running v1.8. This had the same sound, in a fairly busy environment you had to put your ear on the unit to hear it, but it sounds like oscillation/as loud as a quite hard drive spinning. When I changed the unit to high sensitive input detection it cycled off after about 15 mins. Back on medium and no problem (not 100% sure this is the cause)
The Hypex units with the same power rating were dead silent. I have a concern that SevenOaks policy doesn't allow the transfer of warranty although the eBay selling I purchased it from was kind enough to send me the original receipt. The guy in the shop seemed to imply some noise was typical of high power amps! I didn't get to plug in the M33 to see if that had the same problem.
With mine the buzz is audible from within 1m of the unit, but is so faint you cannot hear it at listening, it's present whether there is speakers and XLR inputs or fully disconnected.
Any ideas where (UK) consumer rights does stand? I don't think its right for a £1800 amp to buzz, its sat above a fully passive music server and it sounds like there is a hdd spooling up. I'm reluctant to send it back and wait 8 weeks for them to tell me its operating normally. What warrants a defective fault or allowed noise an amplifier can make?
Just had a response from SevenOak & NAD
"I’ve spoken with our NAD engineer, and he suggests all C298 will make a slight low level due to an inductor in their switching mode power supply. If it’s only audible when you place your ear next to the unit it’s not something to worry about and doesn’t effect it’s performance."
What's your thoughts?