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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
goose
692 posts
 
I agree with pops,  I had a similar problem with an older McIntosh pre amp.  The problem seemed to go away after it got warmed up and it turned out to be a loose solder joint.
decesares OP
2 posts
 
Hello,
sorry for my late answer and have many thanks for your help.I opened it last week and noticed that 1of 4 Capacitors (4,7 uF /63V ) between GND and TT GND were blown.Yesterday I replaced all 4 caps and all Caps 4700uf (blue Philips Type) with new ones(Roederstein) . Today I will test it out.You´ll here from me soon.
dweller's avatar
dweller
3,781 posts
 
Forgive my inexperience but how did you know they were defective? 
decesares OP
2 posts
 
the 4,7uF were exploded , don´t ask me why .But there were no left over parts in the unit, I think this happened to the owner before.The replacement of the other Electrolytic caps are more a general overhaul (more than 25 years in use)than a defect. I have not much trust in the blue philips caps so I replaced the most by roederstein capacitors.I´m working as technician for Lufthansa and repair cabin electronic, former Ißve been working for Kenwood and Akai.But with I am very unexperienced with problems like the popping noise only in MC mode.Never had  a problem like this before with all the amps I repaired in all the time. Really strange ....
dweller's avatar
dweller
3,781 posts
 
Thanks! Glad it's fixed.
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