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Schematic sanity check - dual output preamp w/MV

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  • Schematic sanity check - dual output preamp w/MV

    Hi folks,
    Working on a single channel preamp (gain stage, volume, gain stage, tonestack, master volume(s) cathode follower, out(s))
    I'm trying to configure this with split outputs - one for a power amp, and one transformer balanced to send to the board - and separate "master volumes".
    Would dual cathode followers make sense here, with the MV's before each grid?
    Here is a quick sketch of the harebrained idea, thanks for looking!
    Click image for larger version

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  • #2
    Couple of thoughts:

    Your XLR out is going to sound like crap going to the board. You need to add some filtering to make it sound more like a speaker cab. A good start is to roll off everything above 4-5kHz with a 3rd-order LPF and everything below 100Hz with a 2nd or 3rd-order HPF. This will still sound somewhat flat, though. It takes fancier filtering that more closely mimics the amplitude/phase response of a real cabinet to make it "feel" right. If you are just recording and not using it live, you can use a convolution plug-in with cabinet IRs to properly filter the signal and it will sound good.

    You could skip the volume control on the XLR path, too, if you want. Just design it so it puts out a max +4dBu line level. The board has input pads and level controls, so it is redundant, unless you need to control the level going to FOH or something.

    Also, put a 0.1uF cap across your ground lift switch, otherwise it will likely pick up radio stations when in the lift position.
    Last edited by raiken; 12-26-2014, 06:26 AM.

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    • #3
      Good call on the cap.

      I should mention, this preamp is for bass and the output transformer is wound as such.
      James tonestack.
      Should your filtering advice still apply?

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      • #4
        Originally posted by hylaphone View Post
        Good call on the cap.

        I should mention, this preamp is for bass and the output transformer is wound as such.
        James tonestack.
        Should your filtering advice still apply?
        Bass? BASS??? NOW you tell me!

        Nah, you should be fine without any filtering. It is distortion tones that sound really bad with no speaker emulation. Unless you play a very distorted bass, you're probably ok. A little eq on the board if you have too much top-end, and you're good to go.
        Last edited by raiken; 12-26-2014, 06:15 PM.

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        • #5
          Thanks a bunch

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