[BearMonster]

I have a headphone tube amp Icon Audio hp 8 mk 2 which has for a couple of weeks been giving me the 60hz hum.
 
At first i thought it was faulty tubes so i changed them out with various different 12ax7 & 6sn7 but all have not made any changes at all. Next i disconnected everything leaving only a headphone and the power on which still gives me the hum. next i test it on various other sockets around the house but all still gives me the hum.
 
And the last test putting the volume dial at the lowest with only the power on, using differnet headphones but still the hum remained there. I'm probably guessing it's the caps or something else inside, might have to send it back for repairs but would hate it if they told me they found nothing worng with it.

 

[NA Blur]

Because the hum does not depend on the volume my guess is that it is still bad tubes.
 
If it is higher pitched then take a look at the filter caps, but my guess is the tubes are still bad. I think you need better tubes.

 

[elliottstudio]

First off, isn't UK line current 50Hz?
60Hz(or 50Hz) hum implies line voltage, and that usually happens when you have the unit too close to a 60(50)Hz source like a large power transformer. Since you've moved the unit around the house and still experience the hum, are you certain it's 60(50)Hz and not 120(100)Hz? The higher frequency is a product of rectification of the line voltage. This would imply a bad power supply component, most likely a capacitor or rectifier.