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30th ANNIVERSARY PREAMP

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  • 30th ANNIVERSARY PREAMP

    The other day I was poking around in a marshall 6100 30th anniversary schematic maybe dreaming about building a kind of a three channel guitar preamp, just to know what kind of sound i could get from that. I think I'm doing this kind of things since I watch a youtube video about a all tube distortion pedal that I really like it (https://www.youtube.com/watch?v=olgXiYEBNgo).

    Checking the preamp and power supply schematic of a 30th anniversary I realize that there´s no information about the plate-cathode voltage of tubes, this information (and the whole power supply for tubes) is in the schematic 6100-63-00 and which I have not.

    The final goal here is try to build a pedal using this three channel preamp with six tubes full voltage.

    Any Ideas or comments about this?

  • #2
    The voltages are really not that important. The standard 250-300V DC supply rail with 100k/1K|plate/cathode resistors should work. The channel switching is what is open for many design variations. You could use relays, opto-isolators or Fet's. And combining circuits for cascade stages, or uses totally separate circuits are options. It's not an easy project to be sure.
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    • #3
      Originally posted by guitician View Post
      The voltages are really not that important. The standard 250-300V DC supply rail with 100k/1K|plate/cathode resistors should work. The channel switching is what is open for many design variations. You could use relays, opto-isolators or Fet's. And combining circuits for cascade stages, or uses totally separate circuits are options. It's not an easy project to be sure.
      Thanks for your kind reply, I really appreciate it.

      Right now I'm collecting all the parts and drawing a PCB for the project. I guess I'm going to try the circuits separated while I find a solution for the channel switching.

      If everything goes good I´m going to try to amplify this with two old EL34 that I have.

      I wish the best for you.

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      • #4
        Agree with guitician that this will be a difficult project. Modern era Marshall schematics are very difficult to follow. As far as the switching circuit, this was probably the first tube amp that had a CPU on board, so it will not make things easy.
        Here is a list someone measured for their tube voltages:
        6100 plate voltages question - MarshallForum.com
        Originally posted by Enzo
        I have a sign in my shop that says, "Never think up reasons not to check something."


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        • #5
          Originally posted by g1 View Post
          Agree with guitician that this will be a difficult project. Modern era Marshall schematics are very difficult to follow. As far as the switching circuit, this was probably the first tube amp that had a CPU on board, so it will not make things easy.
          Here is a list someone measured for their tube voltages:
          6100 plate voltages question - MarshallForum.com
          That's a very useful information thanks!

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