DIY attenuator

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by plexikiller, Jan 15, 2008.


  1. plexikiller

    plexikiller Member

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    I'm interested in building an attenuator (such as air brake, hot plate, power soak, weber mass, etc) for a design project in school. I don't want it to just be a couple heavy duty resistors in a box; I'm looking to create a reactive load that simulates the response of a speaker. Does anyone know any diy sites or good reference for this? Even schematics of the above listed resistive loads (cept the mass) would be a great starting point. Actually a good resistive load wouldn't be so bad. This is for my senior design but they're more worried about writing/team work/presentation than the actual complexity of the design..
    Thanks
     
  2. phsyconoodler

    phsyconoodler Member

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    there is no attenuator that can do what you are asking.They cannot drive a speaker like a cranked amp can.Some lose less tone than others but all fall short of turning up the amp.Cannot be done.
    pure and simple.
     
  3. frankencat

    frankencat Lex Luthier Gold Supporting Member

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  4. plexikiller

    plexikiller Member

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    Informative post. I know there isn't an attenuator out there that is perfect. My aim is clearly to try, learn something in the process, and graduate on time.
     
  5. phsyconoodler

    phsyconoodler Member

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    Then you need to re-word your request.You want to build an attenuator.You can't build one that simulates the reactive response of a speaker.You can use a speaker voice coil as part of the attenuator however..but it still cannot move the coil like a cranked amp does.
    You may make the attenuator lose less highs at maximum attenution but you still have the speaker itself to contend with.
    If you find a way to make it work,you will be able to sell lots of them.Ted weber's mass uses a speaker voice coil as part of the attenuation process I believe,but it still has to go to a regular speaker.I have used the mini-mass and it's ok but that's it.
    still has the speaker you use to hear with to contend with.
     
  6. John Phillips

    John Phillips Member

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    There is no reason to be dismissive just because you think it won't sound like a speaker driven harder. The best way to learn anything about how they work is to try to build one that sounds better.

    The really interesting thing is that in my experience the attenuators which sound best are those which make least attempt to duplicate the impedance and reactance of a speaker. The ones that come closest to trying to duplicate the correct curve are those that sound least good IMO (including the Mass, sorry!). I use one of them, the Marshall Powerbrake - which comes even closer than the Mass, and is the closest of any attenuator I know of, so is ideal for use as a test load for amp repair work, but I would be the first to admit there are better sounding attenuators.

    It would be a useful part of this project to try to find out why purely resistive attenuators sound better, since it's counter-intuitive.

    I think you need to look at the way the attenuator drives the speaker as much as the way the amp drives the attenuator. Running an amp into a dummy load (even an attenuator used as one) and re-amplifying sounds a lot better than using an attenuator 'normally', to most people. This means that it's the interaction between the attenuator and the speaker which messes up the tone, not that between the amp and the attenuator. FWIW, the "Ultimate Attenuator" is a load/re-amp system, not an attenuator, and it's widely regarded as one of the best sounding.
     
  7. phsyconoodler

    phsyconoodler Member

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    Sorry if I came off as being dismissive.Keep searching for more info and see what happens.
     
  8. plexikiller

    plexikiller Member

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    Its ok.. I've been on it. Aiken has some great material. I may ditch this as my senior design since most students want to do either something really obvious like build a fuzz pedal or small tube amp, or something super digital and not fun. I need to do this in a group. Either way I'm building it for my own use. It seems the easiest/most effective way so far is to use a T-Bridge circuit. I found some nifty aluminum housed 50w resistors to use in this design that are pretty much enclosed in a heat sink. I've been doing a lot of reading and hope to come up with something better than just that though.
     
  9. plexikiller

    plexikiller Member

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    btw... What is regarded as the best/most transparent attenuator on the market? The MASS has the coolest design but doesn't seem to get the best reviews..
     
  10. John Phillips

    John Phillips Member

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    The Komet/Dr.Z Airbrake (purely resistive), the Hotplate (mainly resistive with some inductive components), the Sequis Richter Control (ditto), and the new Bad Cat Leash (which I think is purely or largely resistive, but I don't know) seem to get the best reviews, but it's amp- and speaker-dependent as to which is the most transparent. It also depends on whether you're looking for moderate reduction or right down to bedroom levels.

    The 'Ultimate Attenuator' does get very good reviews for sound quality too, although there have also been reports of problems with it, and it isn't really an attenuator anyway.

    Remember that the power rating of most high-power components relies on adequate heatsinking or fan cooling, and that some tube amps can put out well in excess of double their rated power when fully distorted, too.
     
  11. plexikiller

    plexikiller Member

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    a member here was awesome enough to email me a layout of the air brake design... seeing as how this is one of the best and has a nifty bedroom feature I will build this as my first design. refinements will come once I truly understand these devices. there is a TON of great information out there, either guitar attenuator specific or general EE papers. btw if anyone is interested in this layout or my exact mouser order lemme know
     

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