Interfacing Low-Output Guitar Effects Processor Directly to Power Amplifier

Discussion in 'rec.audio.pro' started by NDB, Aug 22, 2003.

  1. NDB

    NDB Guest

    Hello All,

    I have a Boss GT-6 Guitar Processor that I would like to run directly into a
    power amp. From what I've been told by an informed source, the output of
    the GT-6 is not strong enough to drive a power amplifier expecting a line
    level signal to full power. Here are the specs of the GT-6:


    Nominal Input Level INPUT: -10 dBu, RETURN: -10 dBu
    Input Impedance INPUT: 1 Mohms, RETURN: 220 kohms
    Nominal Output Level OUTPUT: 0 dBu, SEND: -10dBu
    Output Impedance OUTPUT: 2 kohms, SEND: 2 kohms


    The power amplifier in question has the following specs:

    Input Sensitivity @ 8 ohms: 1.0Vrms
    Input Sensitivity @ 4 ohms: 0.9Vrms
    Input Impedance: 6 k ohms unbalanced, 12 k ohms balanced
    Gain: 32 dB

    Based on this, is it correct to assume that the GT-6 will not be able to
    drive the amplifier to full power? If yes, what do I need to do to correct
    this? Would a DI box like a LR Baggs Para-Acoustic DI do the trick?

    Please advise.

    Thanks,

    Nenshad



    --

    -------------------------------------------------------------
    A One-Man Jazz Band? Believe it!
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  2. Jay Kadis

    Jay Kadis Guest

    In article <vkclfhm00614a2@corp.supernews.com> "NDB"
    <nenshad@cosmiccontamination.moc> writes:
    > Hello All,
    >
    > I have a Boss GT-6 Guitar Processor that I would like to run directly into a
    > power amp. From what I've been told by an informed source, the output of
    > the GT-6 is not strong enough to drive a power amplifier expecting a line
    > level signal to full power. Here are the specs of the GT-6:
    >
    >
    > Nominal Input Level INPUT: -10 dBu, RETURN: -10 dBu
    > Input Impedance INPUT: 1 Mohms, RETURN: 220 kohms
    > Nominal Output Level OUTPUT: 0 dBu, SEND: -10dBu
    > Output Impedance OUTPUT: 2 kohms, SEND: 2 kohms
    >
    >
    > The power amplifier in question has the following specs:
    >
    > Input Sensitivity @ 8 ohms: 1.0Vrms
    > Input Sensitivity @ 4 ohms: 0.9Vrms
    > Input Impedance: 6 k ohms unbalanced, 12 k ohms balanced
    > Gain: 32 dB
    >
    > Based on this, is it correct to assume that the GT-6 will not be able to
    > drive the amplifier to full power? If yes, what do I need to do to correct
    > this? Would a DI box like a LR Baggs Para-Acoustic DI do the trick?
    >


    From the specs, there's a slight difference between the "nominal" output level
    of the GT-6 (0 dBu=.775 V rms) and the amp's input sensitivity (1 V.) If the
    nominal output is really not the maximum output, you're OK. If the nominal
    output of the GT-6 is really its maximum output, you will lose 2.2 dB from the
    maximum output of the amp. You will also lose ~2.5 dB from the relatively high
    output impedance of the GT-6 and low unbalanced input impedance of the amp. So
    you're looking at about 5 dB below the amp's rated output in the worst case.
    Depending on the amp's power output, this might or might not be a problem. It
    might only be ear-splitting instead of ear-shattering. Can't you just try it?

    I use a GT-3 and it has plenty of output level for anything expecting a line
    level signal (and there's a gain adjustment pot on the output.) Unless the
    GT-6 circuitry is significantly different, it should also work.

    I have also found the GT-3 to sound SIGNIFICANTLY better through a real combo
    guitar amp that through any hi-fi stuff.

    -Jay
    --
    x------- Jay Kadis ------- x---- Jay's Attic Studio ----x
    x Lecturer, Audio Engineer x Dexter Records x
    x CCRMA, Stanford University x http://www.offbeats.com/ x
    x-------- http://ccrma-www.stanford.edu/~jay/ ----------x

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