This answer applies to R1 Mk3 R1 Mk2 R2 Mk3 R2i Mk2 MR1 Mk1 MR1 Mk2
The modern ‘switch mode’ power adaptors we use are far more energy efficient than transformer power supplies but occasionally can emit a low level, high-frequency whine when not under load. This typically happens when the unit is in standby mode. This does not indicate a faulty adaptor, but if you experience such an issue and feel that the whine is unacceptable then please contact us for assistance.
If not, please do not hesitate to contact us via our support enquiry form.