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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
pops
2,273 posts
 
Could be resistor, cap, or loose solder joint.  Nice preamp, do you have someone who can work on it nearby?  Most likely an easy fix.
goose
682 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
3,779 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 ....
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