Loud popping noise with Classe Audio SIX pre-amp in phono MC mode


Loud popping noise with SIX pre amp in Phono MC mode.
Hello ,
I´m a proud owner of 2 very nice classe audio amplifiers.I have a Classe Six pre amp and a sevenhundred power amp.Both are very nice sounding, very musically amplifiers.I use it with Infinty Delta/Gamma speakers and sometimes with my good old Infinty Quantum 3`s.The TT is a LINN LP 12 with Lingo ,Manticore Magician arm and an Ortofon Jubille cartridge.Since last saturday I have a problem as follows:sometimes when I raise the Volume at the pre amp there comes a loud popping noise. The amp is going into protection mode (The red LED stays on continuesly) and comes back after a few seconds with light popping noise(DC at the preamp outputs around 180mV) .After a while it dissapears and everything is working fine.Maybe some forum members knows the problem or ad similar experiences with his pre amp.Maybe there´s something wrong with the phone stage?
I am thankful for every help I can get
with best regards
decesares