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MC 257 MKVI humming


RobF

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So I am getting a humming noise from my speakers when I have my preamp connected to the rca inputs of my MC 275, but when I switch them out to XLR there is no longer a hum. The rca cables are new Blue Jeans. I tried to connect a cheaper rca cable I had laying around and the hum was even louder. I also removed and reinserted all the tubes. That same blue jeans RCA cable works just fine with no hum when hooked up to my MC 2205. One thing that did happen today was that the 275 suddenly turned off out of nowhere while I was playing music. Only now am I noticing this hum from the rca interconnects. Anybody know whats going on? 

Edited by RobF
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22 minutes ago, derrickdj1 said:

I use something like this for my subs over the past several years.  It can also be used for a speaker. https://www.crutchfield.com/p_127SNI1/PAC-SNI-1.html?tp=61807

 

 

Thanks derrick. So is this not a problem with the amplifier then and rather something normal with the MC275? Also to note, The humming noise goes away when I disconnect it from the preamp. 

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First things first plug all equipment into same outlet.   Use a ground plug lifter ($2 from home depot).   With a bit of patience and trying same outlet, different outlet, one ground lifted, both grounds lifted, you will find a magic combo (if there are no problems with your gear; it doesn't sound like it if cables solve the problem).  I had a LARGE PA system.   It was almost silent when I lived in one place.   When I moved into another, CRAZY GROUND LOOP.  Took me 2 hours, patience and less than $10 to solve the problem there.... 

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It usually isn't very expensive if you are comfortable with wiring up your own electrical, to get a DEDICATED 30 amp outlet and split it into a dual duplex setup and then all current, noise and other problems will vanish.   I highly advise that and you will notice a difference IMO.  I'm sure others would be happy to say otherwise, but this has been my experience (even currently). 

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Thanks for the replies. Given the layout of my home and space I have the amp connected to one outlet in the hallway and my preamp and turntables hooked up to another outlet in the dining room and my la scalas are placed in my living room 🙄. I got an extension cord and hooked up the amp to the same outlet as the other equipment and the hum is gone thanks Westcoastdrums. Next question is there any modifications I can make that will allow me to keep the amp hooked up to its own individual outlet away from the preamp and turntables and still get quality sound? 

Edited by RobF
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Like I said, modify the outlet(isolated) .   It is CHEAP.  Tap into what you have available on your electrical box.  Dedicated 20 amp is more than enough for most people.   Buy a cheap used line conditioner.   Problem solved.  Sounds great.   Audio advisor has a relatively affordable Pangea line.   I always run amps and Preamp straight into the wall".   Everything else goes into the same outlet isolated on the line conditioner so as to not interfere.   Hope that helps.   

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