Valve DAC - Rhythmic Popping through speakers?

[Gazzip]

Help! I have a rhythmic popping coming through my speakers when my DAC wth a valve analogue output stage is switched on. I have established a couple of things this evening:
1) The rhythmic popping issue is limited to one channel.2) The rhythmic popping starts off slowly, every two or three seconds, and speeds up to twice a second.3) it is unlikely to be a faulty valve. I have swapped the valves with a spare set I have and the problem still persists. Any ideas on on what this might be would be very helpful.

 

[JoelSim]

I think you'd be best giving the manufacturer a call. My Leema developed a problem a couple of months ago (1 month after the end of the 5 year warranty as it happens), and the first port of call was Leema. Sorted now.

 

[andyjm]

Putting to one side why on earth you would have a DAC containing tens of thousands of transitors and then use a valve (of all things) to drive a few feet of cable, the fault you describe could be easily be a capacitor failing. I would have guessed at a HT smoothing capacitor, but as it is one channel only, it is probably in the grid coupling circuitry.

Valves use (in transitor terms) very high voltages, and high voltage capacitors can fail as you describe.

Send it back, and maybe buy one that doesn't have a hundred year old design in its output stage.

 

[Gazzip]

Putting to one side why on earth you would have a DAC containing tens of thousands of transitors and then use a valve (of all things) to drive a few feet of cable, the fault you describe could be easily be a capacitor failing. I would have guessed at a HT smoothing capacitor, but as it is one channel only, it is probably in the grid coupling circuitry.

Valves use (in transitor terms) very high voltages, and high voltage capacitors can fail as you describe.

Send it back, and maybe buy one that doesn't have a hundred year old design in its output stage.

because I like the way it sounds.