BeePre2 right channel pop every 2 or 3 seconds that gets louder with volume

[ConradEdgewood]

All,
I have a BeePre2 that has been working perfectly.  I completed the Stepped attenuator upgrade.  No issues.  Then I completed the output upgrade with balanced.  Now I have a click, or pop, that comes from the right channel approximately every 2 or 3 seconds.  I have a McIntosh amplifier and I can see the power meter go up a little on that side when the pop sound happens.  It gets louder with the volume of the preamp, and is unnoticeable when the volume is quite low on the preamp.  The pop sound is relatively quiet, I would say about the volume of a click when playing a record on a turntable.

I am going to swap the tubes from right to left and see if that helps, but has anyone experienced this, or could think of a possible solution? 

Voltage check of everything is good, checked for missing or bad solder joints.  All good so far.    Thanks in advance.    Eric

[Paul Birkeland]

If it goes away when the volume control is down, that would tend to indicate an issue with the 300B wiring on that channel.  The most likely culprit is a flaky solder joint or unsoldered connection.