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valve preamp modify to DI box?

Discussion in 'Electronic Basics' started by Matt, Apr 1, 2004.

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  1. Matt

    Matt Guest

    Can anyone advise me on following?

    I have a simple valve preamp (based on a 12AX7) which I want to modify so
    that it works similar to a DI box. What I want the device to do is provide
    high impedence ( > 1 Meg) input for a device such as a guitar pickup, and
    convert the signal to a lower impedence suitable to feed to a microphone
    input or line input of a mixer. Prefereably the output would be balanced
    but its not a requirement.

    I understand that the output from the 12AX7 might need a transformer to
    convert it to a lower impedence. I have a quality MC step-up transformer
    (Dynavector DV-6A). Could this be used in reverse if the signal was
    suitable attenuated first?

    Can anyone advise me or point to schematics on the web?

  2. tempus fugit

    tempus fugit Guest

    Is the MC xformer an audio one? If not, it will probably trash the sound. If
    you go to they have some application
    notes that should help. I would think that you would also be looking for a
    line level output, and since you're going to the trouble, you might as well
    make it balanced.
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