OK. Swap the speaker leads over at the amplifier outputs - take out the red cables FIRST, re-insert the red cables LAST.
Does the noise change channel or stay in the same channel?
In that case it points to a fault on one of the amplifier boards. I will double check with Tomasz that I haven't overlooked anything...then PM you with the next steps.
NO!! I AM NOT RECOMMENDING THAT. IT WAS A JOKE. SUCH TESTS SHOULD ONLY BE CARRIED OUT UNDER LABORATORY CONDITIONS AND BY QUALIFIED ELECTRONICS ENGINEERS.
Speakers - Monitor Audio Silver RX2
Cables - NVA LS1+LS3, SSC, Gotham S/PDIF, IBRA Optical
Digital - NAD C516BEE, SONY ST-SDB900 DAB TUNER, TEAC UD-H01 DAC
Analogue - Pro-Ject Debut Carbon Esprit SB, Graham Slee Gram Amp 2 Phono
Cans - Grado SR80, ATH-M50X