How to do a -16db attenuator for a guitar amplifier

Discussion in 'General Electronics Chat' started by Oldwolf, Dec 25, 2008.

  1. Oldwolf

    Thread Starter New Member

    Dec 25, 2008
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    Hello, guitar amps are a bit insane, sound good only at healthy volume. Since I want to use mine at home, I need some simple passive network before the 8ohms speaker in order to reduce the overall spl by at least 16db.
    What values should I use, and what type of attenuator? Thanks a lot!
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    An attenuator is never used between the output of an amplifier and a speaker. It is used at the input of the amplifier. The amplifier probably already has an attenuator. It is called the volume control.
     
  3. Oldwolf

    Thread Starter New Member

    Dec 25, 2008
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    Okay, so let's call it a power soak then. Of course I could buy a new one, but they are fairly expensive, and I don't need much features anyway. Main issue I have is a high noise floor (and no way to fix it, because of fixed-bias in my amp...) I can't cope with at home.
     
  4. Audioguru

    New Member

    Dec 20, 2007
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    I think you want your amplifier to produce as much clipping distortion as it can. Then you want to reduce the level that the amp feeds to the speaker.

    A huge, heavy and expensive volume control can be connected between the output of the amp and the speaker. It is big because it throws away most of the amplifier power as heat. Then the amplifier won't be able to damp the resonances of the speaker.
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
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  6. Audioguru

    New Member

    Dec 20, 2007
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    An L-Pad was used with high output impedance tube amplifiers so that their load was always the same. It ruins the excellent damping factor (extremely low output impedance) of modern solid state amplifiers. The modern amplifier has an output impedance of 0.04 ohms and less so it can damp resonances of a speaker very well. With the L-pad in between the damping is ruined.

    But the boomy sound caused by poor damping will be another effect for the horrible guitar's sound.
     
  7. floomdoggle

    Senior Member

    Sep 1, 2008
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    Hey Oldwolf,
    First try a rug to dampen the room. Are you looking to keep the ring, then the volume controls on the guitar are the best attenuators. If it is fuzz, or clipping, your main volume control shouldn't change the waveshape. What kind of music do you play? And what is your rig? A stage amp is for stage. Try the old favorite Fender Champ. No reverb, but great for a small room. Wish I still had mine.
    Dan
     
  8. Oldwolf

    Thread Starter New Member

    Dec 25, 2008
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    Thanks a lot, guys, I think beenthere has found exactly what I need. In fact I only want to get rid of the huge noisefloor of my 20 watt MesaBoogie, sort of a passive noise-gate. Since Mesa doesn't install bias justage pots there is no other way to make their amp reasonably quiet at home. The sound is made in the preamp department, no power tube saturation asked in this very case.
    I expect some loss in the frequencies, as audioguru says, but given the low price of the experiment I'll do it anyway.
    I'll tell you the results in a few days, thanks very much for your help!
     
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