Unidentifiable popping sound


Not 100% sure it goes in this forum — apologies if there is a better place.

For 6 months now, something in my system is making a clicking/popping sound. It usually happens 15 minutes after I power things up, or about 10 minutes after I power them down. It can also happen spontaneously when everything is technically on standby. I actually have a recording of it, but not sure how to upload here. Any ideas?

Preamp — Nagra Jazz (possible) (it happened with both old and brand new tubes)
Amp — Nagra Classic Amp (possible)
DAC/Source — PS Audio Directstream (possible)
Phono stage — Pure Audio LV-1 (probably not)
TT — Clearaudio Concept (definitely not that)
Cables — Luna Orange (also, definitely not that)
 

128x128andbaron

I had this problem with my PS Audio Directstream dac when using the bridge.  PS Audio was very helpful and sent me special firmware updates and a new bridge to try but the popping continued.  Finally, they took back the bridge.  Things sound very good even without it.

Popping sounds when there are tubes in the signal chain can be caused when the tube loses contact with the circuit -- bad tube, loose socket, or socket to wire or socket to board solder joint. Usually happens when heating up and cooling down as the bad solder joint  shifts with change in temperature. 

Substitute another preamp to rule this out.

I'm not sure if this will help, but I experienced a similar crackling sound and it was a cable shield that wasn't earthed. Once it reached a certain level it discharged across the inner insulation.

It was a quality brand subwoofer cable with terrific shielding. Problem was it wasn't earthed. After slicing back a slither of the outer protection I gently soldered a wire to the shielding and connected it back to a central earthing point. Fixed.