Valve Newbie Help

I have my PC connected to an Async Abrahamsen DAC then to an Audio Space AS-2i valve amp. The amp made a low level fading crackle and no more music. As I am new to valves does this mean that one or all need changing. It has 7 tubes which are 4 tall ones and three short ones. The tall ones for which I have 4 spare say EL84EH Electro Harmonix made in Russia 06 11.
The 4 Tall ones that are in the amp and I assume maybe valves are marked 6n14n-EP 9103, there is other markings on these so please let me know if its information you need. The small ones that are in the amp are marked audio space 12AX7.
All the valves are still lit can this be like this even with no sound ?
Any help would be appreciated

 

Now then guys your not gonna believe what the cause was. Just had a thought that 24 hours ago I freed up some USB ports using an external hub and plugged the DAC into it. Well just replugged the usb into a port on my pc case and were back in action. Im going to try some other valves. To be honest im really enjoying listening to this amp and DAC and at some stage soon will look out for a better amp. Its looking grim for the solid state Naim in my living room

 

Glad you got it sorted.

Don't be too hasty with the Naim. The results you get from small valve amps are very loudspeaker dependent.

 

Right I didnt realise Rob. The system speakers for this office setup are a £250.00 pair of DIY design speakers bought from a guy in Huddersfield through Ebay. I went had a listen and were very impressed so I picked up a pair. The guy (Roland) sells quite a few pair and I believe they are Proac copies, loosly !
There about 88db so the amp can easily push them, but for the money owe me nothing and are a good listen imho. I am waiting for a local bake off to hear some unbiased oppinons.
Regards
Dave