I have a Naim DAC V1 and I seem to have a problem with the headphone output on the DAC. Every now and again the DAC goes mute after a few minutes of play when my headphones are plugged into it. I can unmute but it cuts out again after a few seconds. Unfortunately I only have one pair of headphones to test with, but when I plug them into my amp’s phono jack I don’t get the problem. Do you have any idea what might be causing this? I’ve emailed Naim support but I never get a reply.