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Mesa 400+ and tube-changing

Discussion in 'Amps and Cabs [BG]' started by carl-anton, May 2, 2002.

  1. Hi,
    Can anybody describe how the Mesa 400+ would sound like, when it needs new tubes. A friend of mine owns one, and though it has a nice tone, it sounds like it can't control it. The sound is very blurred and unfocused, and the low freq, seem way too boomy. (in comparison to my SWR750, that is). Would new tubes give a more focused sound, or is this just the way a tube amp sounds?.
    I'm asking because I can get a 400+ with 2x15 fairly cheep, but I have no experience in tubes yet.

  2. TCollins


    Apr 4, 2000
    I was wondering the same thing! I have a Mesa 400+ that will be two years old this coming Sept. I understand that Mesa reccommends changing your tubes every two years (right?)--Also, does this mean that you should change ALL the tubes including the four 12AX7s?
    How about some help from you veteran Mesa 400+ owners? What should we be listening/watching for when it comes to changing tubes?

    Many thanks!!
  3. Unless you have been are using that amp every night for the last two years I wouldn't worry too much about it. The 400+ is like playing through a rainbow IMO. If you do decide to swap it is very easy as the Mesa's are a fixed bias. Just stick the new tubes right in there. My drummer dropped mine so I ended up swapping my old 6550's for some newer 5881's. I got a far deeper bottom and a VERY solid tone. that was fun!
    Your pal's amp shouldn't sound boomy. have him run it fairly flat ( all the controls at "5") w/o that graphic and see what he thinks. the 400+ needs very little eq-ing to sound good.
  4. Big String

    Big String Supporting Member

    Apr 22, 2000
    Northwest Indiana
    I have two of them.
    A tube change out can be expensive. Make sure that's what it needs. It could be just one pair of tubes. The 400+ not 400 are wire in parallel. There are 12 power tubes and 4 preamp tubes.

    The power tubes (big ones) are in two rows and get the hottest. Looking at the amp from the back from left to right, the inside row is number 1-7 and the outside row is 8-12, but when you change power tubes do it in pairs. EX. if your number one tube went bad you would change 1 and 8. That is sort of a standard according to Mesa. There some variables to that. EX. If the tubes are brand new which just happened to me, one didn't look right and the supplier gave me a new one, in which case I just replaced the one tube. Always make sure your hands are clean or use cotton gloves and never force the tube in or out. Make sure the amp is off and unplugged and tubes are cool to the touch.

    The preamp tubes (small) last a long time and are easier to diagnose. Again looking from the back of the amp, the far right preamp tube is the MASTER preamp tube. Master tube feeds directly to the power section. The others are more for tone etc. I'm sure somebody more qualified could explain that one better.

    There could be other things wrong with the Boogie your looking at, so don't be so fast to pop for some tubes. Have a good amp tech look at if first. It is probably the tubes depending on many things, like how it was taken care of. EX. Powering up and down. Weather or not it was started up with a load on it. (speaker plugged in to amp) Tube amps are pretty touchy until you get used to them. To me they provide the very best tone and power. I truly love them.

    My recommendation for tubes. Power =12 Svetlana 6L6GC and the preamp =4 the 12AX7EH (electro harmonics) Cost about $210.00 for all. Again, tubes can change the tone and power drastically, so be careful what you spend your money on. Follow all these rules and welcome to tone heaven.

    Note: there are some obvious tests you can do. Let the amp warm up on standby for at least a few minutes. In a dark room, power it up making sure the amp has a load on it first. Notice that the power tubes all sort of flash on with a blueish illumination in the main body of the tube. They should all look about the same with the brighter orange glow toward the top of the tube on the filiament part. If one or more of the tubes are dying or going micro-phonic it will probably be pretty noticeable. You preamp tubes light up too depending on what type you have to see the glow. Some are hard to see. With pre's you can hear a hiss as you turn up the master volume and maybe some crackling like bacon frying. That really doesn't mean there bad but some are pretty noisy, that's why I changed to the EH.

    Hope that helps
  5. Big String

    Big String Supporting Member

    Apr 22, 2000
    Northwest Indiana
    Time to change tubes???
    Loss of power. Tubes naturally start degrading from new. You will notice noise, more break-up, clairity not as good. You have to apply different tone settings to get what your used to.

    Get good tubes! Read, research. Let your ears tell you what you like. Pre amp tubes are much cheaper to experitment with.

    Take good care of your amp. read previouse post tips. Don't let your Yahoo bandmates handle your amp. I saw my guys bumping mine around like a box of Kleenex once. Actually the tube and amps are very hardy. Just be careful.

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