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5814/12AU7 Preamp Tubes for lowering Gain.

Discussion in 'Amp Central Station' started by Red Planet, Dec 1, 2007.

  1. Red Planet

    Red Planet Tele-Meister

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    Got a stash of these a while back. They are the military version of the 12AU7.

    I really like these tubes for making a loud amp quieter and taming some high end spikyness. Just wanted to post this for those that might want to try it.

    I have a 67 Bassman that is a little on the loud/hard side and has just a tinge of harshness in the high end with the Emi Speaker I paired it with. Not bad mind you but it just needed something to settle it down and smooth it out.

    I stuck a 5814 Raytheon Black Plate in V1 and V3 and a Mullard ECC83 in V2 with an RCA 6201 in V3. The power section has a set of new =C= 6L6's in it.

    This combination took this thing down a huge notch and let me Crank it for a softer more pleasent sound. Jumpering the Channels with both Volumes dimed yielded a much user friendly Volume and Tone to my sound with this Amp.
     
  2. mistermullens

    mistermullens Poster Extraordinaire

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    I did something similar with my Epi Valve Jr head. Quite a different animal than your Bassman, but I replaced the 12AX7 with a NOS 5751. It smoothed out the sound a bit and also helped with my volume issue. I can now play it at home through a 2x10 cab with no requests from the wife to "turn it down."
     
  3. Red Planet

    Red Planet Tele-Meister

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    I dont even know what the db difference is of all these. Seems like I remember the 12AX7 being 100 and the 5751 being 70. I dont know what a 5814 is. I just know I love these tubes. I wish I had tried these in amps through the past that had too much gain. The Bassman dosnt have a lot of gain but its too loud like it is.
     
  4. Opaltone

    Opaltone Tele-Holic

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    5814 is just about the same as a 12AU7 - about 20% of a 12AX7. I was just using a Raytheon black-plate 5814A (3-mica) in my Victoria Regal II today. They've got more rolled-off highs than many other 12AU7 I've tried (about 30 kinds), but still retain excellent liveliness and tight bass.

    - Thom
     
  5. Red Planet

    Red Planet Tele-Meister

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    Thanx for the reply. I have a pile of these 5814's. Its hard for me to tell what they are though. They were NOS but had been laying out in a wharehouse for many years. The Boxes had rotted off and they were so dirty I had to clean em up. When I did it took the paint off of em but left the etching.

    There were Sylvania, Raytheon, Tung Sol, RCA, GE, and others in this big box full of tubes. There were 6201's, 5814's and 12AX7's among others.


    Anyway these things really did a number on this amp to make it more livable and I thought some might want to know.
     
  6. Opaltone

    Opaltone Tele-Holic

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    Post pictures of the unknowns, either here or TGP (when it is back up), and we can probably help you i.d. them.

    - T
     
  7. Red Planet

    Red Planet Tele-Meister

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    OK when I get a chance I'll take some Pics.
     
  8. 2ndstringer

    2ndstringer Tele-Meister

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    My Crate VC 508, which is a 5 watt amp with one preamp tube and one EL 84, came with a Sovtek 12AX7. So equipped, there was no possibility of anything resembling a clean sound, so I put in a GE 12AY7, which improved things quite a bit. I have never been quite happy with the sound of this amp, however. I know there are further mods that can be done, but I don't feel competent.

    With single coils it is a bit harsh. With humbuckers it is a little sweeter, but forget about clean. I think I have read that there are problems with the design.

    Anyway, going to a lower output preamp tube can make a big difference. There's 12AX7, 12AY7, 12AT7, 12AU7, maybe more. I forget how these all compare in output.

    John
     
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