HELP...weird noise with my mesa dual rectifier....

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Bronze, Jul 4, 2006.


  1. Bronze

    Bronze Member

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    Location:
    Portland TN
    My mesa boogie dual rec. amp head is making some kind of weird noise, and was wondering if anybody could give me some advice before I took it to a tech(and spend loads of money). It's weird, it sounds kinda like a TV turned to a channel that doesn't get good signal(think about the movie, The ring. Where the t.v. comes on thats the noise i'm talking about). But its not a steady hhhiiiiiiiiiiisshhh. Its in and out. And sometimes its not real bad(now talking about how loud this noise can get), but there are times it does get loud. I also know that the problem lies with the amp, cause when the noise started I unpluged everything, so now, nothing went to the amps input or to the effect loop, it was just a speaker cable connected to the head and to the speaker cab, and it's still making that noise. Another thing, I tried turning down the master volume on my amp and the noise still comes through. I replaced the tubes about 6 months ago so IDK if thats the problem or not....And I tried different speaker cables and speakers....
     
  2. Rich M

    Rich M Member

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    Sounds like a noise problem. :horse

    Could be a bad tube. Or it could be dirty/loose sockets. Could be a bad part (resistor,etc.). If you have a spare set of tubes, try swapping them out and also cleaning/retensioning the tube sockets.
     
  3. John Phillips

    John Phillips Member

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    If turning down the MV doesn't cure the noise the problem is in the power section. (I'm assuming you have the FX loop switched off, not simply nothing in it).

    First, remove two of the power tubes (inner or outer pair) and see if the noise goes away. If it does, one of the tubes you've pulled is the cause. (Swap one of them for one of the two in the amp and try again if you want to find which one.) If not, swap both of them for the other two. If no combination of two tubes makes the noise go away, try removing one of the rectifiers (with only two power tubes in the amp). If that doesn't cure it, try the other one.

    If none of that works, try swapping the phase inverter tube (the preamp tube closest to the power switches). You don't need a new tube yet, one of the other ones will do.

    If it's none of that, it's probably a failing resistor, a bad tube socket, a faulty channel-switching LDR, or something else that needs a tech.


    If it does prove to be a power tube, you're best to replace them as a set. Keep the three good old ones as spares.
     
  4. Bronze

    Bronze Member

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    Man I can't believe it!! It is the power tubes. I just replaced those things like 5 months ago. I'm definitely not going back to the chinese-mesa tubes, what are some high quality tubes I can put in it?
     
  5. John Phillips

    John Phillips Member

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    NOS anything, but I particularly like the JAN-Philips/Sylvania 6L6s and 7581As in Mesas.

    Yes, they're worth it. Better reliability, FAR better tone and more (measurable) power. No modern tube is even close IMO.

    If you can afford it, do the whole amp. You will hear the difference. You don't need the most expensive types, or even to buy 'new' old stock, especially for preamp tubes. My amps are loaded with old used GE preamp tubes mostly. They're so cheap on ebay and elsewhere that you can get the odd bad one and still come out ahead if you buy plenty. If you want NOS for peace of mind and warranty, they're still better value for money than the new junk IMO.
     

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