AKG SolidTube problem - solved!

Discussion in 'Microphones (live or studio)' started by DonnyThompson, Oct 4, 2014.

  • AT5047

    The New AT5047 Premier Studio Microphone Purity Transformed

  1. DonnyThompson

    DonnyThompson Distinguished Member

    Nov 25, 2012
    Akron/Cleveland, OH
    Home Page:
    Several months ago, I had a conversation with Bos about a mic I own - the AKG Solidtube, and how it was making some noise after it heated up.

    The noise was similar to what you would hear if you took a tissue or a paper towel in your hand and scrunched it.

    Yesterday, I dug the mic out again, thinking I'd pop the top on the power supply to see if there were any obvious indicators - like blown caps, etc...

    I didn't see any issues, so, I decided to take the mic apart. After doing so, I decided that I would replace the tube - I really didn't think it would solve the problem, but I figured that while I had the mic apart I might as well...

    So, I took out the stock tube, which was a National 12AX7/ECC83 - and because I didn't have an exact match to replace it with, I ended up using a Mesa 12AT7/ECC81, from a box of spare tubes that I keep around.

    I fired the mic up again, let it warm up for about 15 minutes (long past the time the mic would have taken to start making the noise I'd been hearing ) and.... silence!!
    The noise was gone. ;)

    I recorded some vocals through it, and found the tonal coloration to be very pleasing.
    It was very warm, yet with a very nice upper end edge ( not the bad kind of edge) ... it was a very pleasing "presence" yet still maintaining the warmth... I actually found it to be more appealing than what I'd heard when using the stock 12AX7.

    Replacing the tube wasn't at all difficult. Once I found the owner's manual online and read about out how to take the mic apart (just 3 small Phillips screws on the bottom of the mic where the power supply jack is) it took less than 5 minutes to open the mic, replace the tube and then put the mic back together.

    I am now wondering what different tubes might sound like; perhaps a Telefunken 12AX7? :)

    Yeah, I know... putting a Telefunken tube into my mic won't turn it into a Telefunken mic. ;)

    Anyway, just thought I'd share.

  2. pcrecord

    pcrecord Quality recording seeker ! Distinguished Member

    Feb 21, 2013
    Quebec, Canada
    Home Page:
    Good for you Donny ! Reviving failling gears is always rewarding and good on the budget !

    I'm fairly newb on tubes and find it more and more interesting to investigate.
    Since I got my used LA610, I'm wandering if I should get a set of new tubes to make sure I start to use it to its maximum potential.
    On the other hand, it sound very good like it is !! On UA website, they say a tube will sound the same up to the day it fails. But many people say they loose quality over time. Sorry, I should start a new thread on that instead of hi-jacking yours ;)

    I wonder where I got the sickness of wanting to make everything better !!! :)
  3. Davedog

    Davedog Distinguished Member

    Dec 10, 2001
    Pacific NW
    The AT's have less gain the the AX's and are sometimes the proper choice for mics and other relatively sensitive circuits I'm not surprised you like it simply because of the lack of noise.

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