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Thread: replacement tube

  1. #1
    tc4b's Avatar
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    replacement tube

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    I have received a cheap little tube preamp (presonus tube pre) which seems to do nothing. I have heard replacing the tube will improve it drastically, but there are so many freaking tubes I have no idea where to start. Can anyone reccommend a good replacement for cheap? I want to use it for my mic (groove tubes gt55) and possibly as a direct box for my bass (guild, no active electronics).

    In case it matters, I record on a digi 001, all real instruments, no synths.

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    Zetajazz44's Avatar
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    That pre should have a 12AX7 tube... I've read a few who replaced it with a New-Old-Stock "GE JAN 12AX7" with better results... I've also read of some replacing it with the "Electro-Harmonix 12AX7"...

    If you Google with these terms, you should find plenty of reading.
    [COLOR=RoyalBlue][SIZE=4][B]Zetajazz44[/B][/SIZE][/COLOR]
    [SIZE=1][I]"If the "Music Business" was a yard stick, 3 inches of it would be the music... The other 33 inches would be the business..."[/SIZE][/I]

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    Big Kenny is offline Been Here, Posted That
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    It's a 12ax7, I don't think you will notice a huge improvement though. That pre is pretty much the entry level for the presonus line. Dual servo, no caps should run pretty quiet but I have had no direct experience with this unit.
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    Zetajazz44's Avatar
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    Quote Originally Posted by Big Kenny
    It's a 12ax7, I don't think you will notice a huge improvement though. That pre is pretty much the entry level for the presonus line. Dual servo, no caps should run pretty quiet but I have had no direct experience with this unit.
    That's what I was thinking when I made my ealier post... They use what some refer to as a 'starved plate' tube... Meaning that the tube runs at very low voltages like 9-12 volts... 'Real tube' devices have up to 300 volts on the plate... starved plate tube devices are noticeably sonically inferior to the high voltage devices.

    I've read reviews both ways though... Some like it, some say the noise it puts in makes it totally unusable... I've personally never used one though... BUT I see alot of these types of posts on this board and since they are not too expensive, I ordered one last week to try out... I figure after I use it/hear it, I'll be able to give a better opinion when responding to posts dealing with these types of devices...

    Some where on this forum, a guy posted a method for bypassing the tube all together... He said it was much more usable in this configuration... When I get my preamp, I plan on testing it in several configurations with different brands of tubes and bypassing the tube as well...

    We'll see how it turns out...
    [COLOR=RoyalBlue][SIZE=4][B]Zetajazz44[/B][/SIZE][/COLOR]
    [SIZE=1][I]"If the "Music Business" was a yard stick, 3 inches of it would be the music... The other 33 inches would be the business..."[/SIZE][/I]

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    tc4b's Avatar
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    Tube kinds...

    I have read a lot f descriptions of tubes, and frankly it's greek to me. What should I look for in a vacuum tube I plan to use in this way? Is there a difference in tubes used for guitar amps and those used for preapms for vocals?

  6. #6
    SonicAlbert's Avatar
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    The TUbePRE can be very quiet, it's more llike user error when they are hissy. You have to split the gain basically equally between the tube drive and the gain knobs. If you try to do all the gain with the "gain" knob it will indeed get hissy when you push the knob past the 12 o'clock position.

    The tube drive is extremely clean on the TubePRE, it will not break up until well into the high volumes. So the way to get the best sound out of the tube pre is to *first* use the tube drive for volume up to about 12 o'clock, then add any more volume needed with the gain knob. This will get you a clean quiet preamp that really sounds pretty good for $99.

    But if you try to do most of the volume with the gain knob and then "add" a little tube drive for flavor, forget it, you'll get more hiss than you'd want. You just have to use this little preamp the way it wants to be used.

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    tc4b's Avatar
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    Um...

    So, are you saying I don't need a new tube? I shouldn't do that? I'm not really sure how that last reply relates to my question.

  8. #8
    Big Kenny is offline Been Here, Posted That
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    First try the advice given, a new tube will help but it won't make the pre suddenly wonderful. You might even try a 5751, has about 30% less gain than the 12ax7 but you don't need a full push anyway and it's a little smoother. Here's a couple for < $20 but do a search for NOS 12ax7 or 5751(google, not search here)
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    SonicAlbert's Avatar
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    I was responding in part to Zetajazz44's post about how some people have said the TubePRE was noisy. All I am saying is that it needn't be if you use the available gain properly.

    As far as replacing the tube, I personally don't think it will make *that* much difference in this particular unit. Certainly, I don't think there would be any point in replacing the tube with a "clean" tube, as the unit already sounds clean.

    If you really want to try out tubes, I'd say go for a more colored tube, one with a distinct sound or characteristics. Maybe a NOS GE or Sylvania, or something like a Telefunken or Mullard. Starting out, just stick with 12AX7's as that's what's in there now.

  10. #10
    punkin's Avatar
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    It's doubtful you will notice a significant change in performance. If you've got other higher end stuff (guitar amps or tube mics) which could benefit from a better quality tube, you might pick one up that way it won't be wasted money but otherwise.

    The 12AX7 tubes can range from dirt cheap to pretty spendy. Here are a few sites you might check out;

    http://www.vacuumtubesinc.com/
    https://secure.tubesandmore.com/
    http://www.vacuumtubes.com/
    http://www.samedaymusic.com/browse--2588

    There are lots of places out there...give Google a shot.

    Good luck
    She's not the boss of me

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