MX110Z Buzz in left channel. Hard to track the source

[MadcapLaughs]

Hello friends,

Its my turn to post one of these threads, I currently have a low level buzz coming out of the left channel of my preamp through my speaker, although its not audible after standing about 3 feet away, its definitely there and buzzing away. I have swapped R and L input cables from the main jacks and the buzz followed to the right channel, which confirms its in the left part of the preamp. I briefly took it to a local tech shop but didn't fully check it in for repair as the oscilloscope did not immediately pick up any buzzes or noises internally. It does not change channel using the reverse switch either. Any ideas before I check this thing in for a while? Its sounding really nice and behaving itself otherwise. Here are some other troubleshooting steps I have taken with no improvement:

-Swapped speakers
-swapped input cables, swapped in a different power amp.
-swapped out speakers cables
-swapped all tube matching left and right locations subbed different tubes altogether.
-reversed power cable prongs, swapped power strips, and tried different electrical outlets for the entire system
-thoroughly cleaned all tube sockets and input jacks on the back panel with deoxit.

*new discovery:

With the preamp unplugged completely from the power strip and turned off, and the power amp plugged in, powered on, and still connected to the MX110, im getting the same buzz in the left channel and totally quiet on the right through my speakers. When I take the rca inputs and disconnect them from the pre amp and power amp but leave the power amp on, the buzz is in both channels. Strange times, im guessing there is a grounding issue, but I cant figure out if its from my MX110 or the power amp.

 

[dcgillespie]

One thing you might try is applying some 100% Deoxit where the output jacks mount to the chassis on the preamp (both on the inside and outside). The ground connection between the chassis and the jack is effected by a stamp fitting of the jack. But if/as the chassis and jack become rusted/corroded/compromised over time, then the actual ground connection to the jack can become compromised as well, and can cause all manner of weird problems. Even if this isn't the problem, it's still a very worthwhile effort if only to ensure that it isn't the problem.

Dave

 

[MadcapLaughs]

Thanks for the reply Dave I appreciate the input. Unfortunately the deoxit spray didn't resolve the low level buzz, I thoroughly doused the main out jacks. I will say my MX 110 chassis does have a decent amount of corrosion. Tracking this down seems fairly difficult. Especially since the buzzing happens even with the preamp unplugged from the wall but still connected to the power amp when powered on.

 

[dcgillespie]

OK, are you using separate mono power amps? If not, what stereo power amp are you using?

Dave

 

[MadcapLaughs]

I am currently using a “Classe Seventy” power amp. Ideally I would be using my pilot SA 232 tube amp but a few techs have been unable to solve the red plating on that amp, no matter the tubes and caps used. I do have a knight KB 85 being worked on but haven’t used it yet.

im in a bit of stereo hell at the moment.