Attenuator DIY info needed

Discussion in 'DIY Amp Forum' started by Jimi Lightning, May 3, 2021.

  1. Jimi Lightning

    Jimi Lightning Most Honored Senior Member

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    Not sure if this goes in the Amp forum or the Stompbox forum..

    An Attenuator seems to be a very simple build. However I have a question

    I have a Marshall cab ( 4 x 8ohm speakers 100watt)
    I also have a late 60s Marlin cab ( 1 x15” speaker 8ohm 25 watt)

    Looking for recommendations for the proper L-pad to build the interface.
     
  2. RobZ69

    RobZ69 Senior Stratmaster

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    The wattage of the cabs is not relevant.

    But you will need an Lpad that can handle the wattage of your amp comfortably, to avoid it heating up too much and having to resort to active cooling (which is not too complicated... just add a battery powered fan)

    Assuming your amp also is 8ohm you'll need and 8 ohm Lpad too.
     
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  3. Jimi Lightning

    Jimi Lightning Most Honored Senior Member

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    The wattage I referred to was the amp.:)
    I was going to add a battery powered fan as a cooling mechanism.
    What confused me with the Marshall is that its 4 x 8ohm speakers so I was unsure.
    I’ll assume the Amps are 8ohm as its driving 8ohm speakers.
    Great info thanks!
     
  4. dante1963

    dante1963 Senior Stratmaster Silver Member

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    Just an observation...there are two types of attenuators, resistive and active.

    Those simple resistive attenuators are very inexpensive—which is good—but you may find that they change the tone of your amp in a way you don’t care for.

    Some people describe it as “throwing a blanket over the amp.”

    Although, ymmv. It’s definitely worth a shot.

    Good luck with your project!
     
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  5. Jimi Lightning

    Jimi Lightning Most Honored Senior Member

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    Ive seen some designs with a Treble fix to eliminate that. Not sure if its effective as i have no experience with Attenuators.
    End state is a Peter Green ish overdriven blues tone.
    Thanks for the well wishes.
     
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  6. RobZ69

    RobZ69 Senior Stratmaster

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    Ok... anecdotal but, I've built a very cheap lpad based attenuator and I don't experience that 'blanket effect'.

    I did buy the components to add a 'treble by-pass' but never installed them.

    (Just like the 8/16ohm switch)

    I don't use it on a 100w amp though (15w and 18w) so that may make a difference.

    On a 100w amp I'd go for at least a 150w Lpad. Or 200.
     
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  7. Alex_C

    Alex_C Strat-Talk Member

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    The speakers are 8ohm, but they can be wired in series, in parallel or a combo of both. I'd guess each pair in series and then those two pairs paralleled, that would give you 8ohms, but that is a guess. They could be in series for 32ohms.
     
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  8. StratoMutt

    StratoMutt Most Honored Senior Member

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    Worth a look if you have not been there: https://tedweber.com/gadgets/attenuators/
     
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  9. Alex_C

    Alex_C Strat-Talk Member

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    Double the L-Pad wattage to be safe. I've burned up an L-Pad that was rated for 30 watts with a 20 watt amp.
    Install a high pass filter, it sounds better with one, imo.
     
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  10. simoncroft

    simoncroft Still playing. Still learning! Silver Member

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    The technical knowledge of you guys is definitely way beyond mine, but I had a repair guy build me an attenuator back in the 1980s. He based his design on the idea that my Fender Bassman 50 needed resitive attenuation. It totally messed up the tubes/valves, and I was really bummed. The whole amp went microphonic, and the tubes were glowing all sorts of colours.
     
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  11. StratoMutt

    StratoMutt Most Honored Senior Member

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    Even better: https://tedweber.com/attenuator-faq/

    Maybe they'd ship one of their attenuators as a kit?
     
  12. joe_cpwe

    joe_cpwe Senior Stratmaster

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  13. archetype

    archetype Senior Stratmaster Silver Member

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