Need advice with clicking noise from my tube amp


I have a Don Sachs tube preamp and amp.  Recently, I notice a consistent "clicking" noise, about 2 seconds apart, from both of my speakers while listening to my system.  I don't recall the clicking noise changing at different volume levels. I swapped the Sachs amp for two other amps, both solid state, and there was no noise, so I concluded the issue was with the tube amp.  

I took the amp to a topnotch tube tech who listened to it in his system for several hours and did not hear any noise, clearly not the clicking I heard.  The tubes were checked and the biases is spot on for all four KT88's.

I asked Don about the possible cause and he is stumped if it can't be replicated with the amp in a different system.  One possible thought was that the amp is picking up some RFI from some source, but I can't imagine what that source might be.  I don't want to have to build a Faraday cage around my rack, as if I had the KSA's  to do that.  

Any thoughts from you folks would be very much appreciated. 

whitestix
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It started a couple of weeks ago and I noticed it several nights in a row.  If it is a hamster (hard to imagine one in my area) operating nearby, is there anything I can do, system-wise, to alleviate the issue?  Perhaps I should stroll around the neighborhood and check for tall antennas?

I'm not sure if this will help, but I had a ss receiver years ago that made that same noise. It turned out to be a bad connection and a tiny spark was jumping across and ticking steadily as you've described.

I had a weird noise like a "tick" coming through my Quicksilver mono amps.   It drove me insane trying to figure it out.  

Turned out be a Glade Plug In air freshener.  When it turned on to warm the scent pack periodically thats when the noise appeared 

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What else is on that circuit? Any new appliances? When it’s happening, can you see what else is running at the same time, what’s plugged in and running? 
Move all the wireless devices away from the system when this clicking starts. See if anything changes. 
If the amp is plugged into power conditioner, try running it directly from the wall. 

To narrow it down, I would try running an extension cord to another outlet (not on the audio circuit) and see if the problem repeats. 

Gents,

I got the amp back from the tech and have been playing it all day.  The clicking noise is gone, but I'll see if it returns tonight.  I appreciate all the suggestions and will keep my fingers crossed. 

Ain’t hifi fun?  I’ve never had any noise issues for fifty years and last year my new integrated amp started to buzz loudly.  Turns out my wife was using a space heater in the other end of the house.

All the best.

Yea this really sounds like an interference problem. This will be fun to track down….