# Dummy Load Box - Who here uses them or knows about them?



## prodigal_son (Apr 23, 2009)

After reading up on these, I can see why it might actually be a good idea to use one if you are after a specific hotter tone (i.e. Van Halen I) and want the full flavour of your effects to be appropriately perceived over a cranked tube amp's break up/volume. For those who are not in the know, one would potentially use a dummy load box as follows:

Maxed tube amp > speaker output > dummy load box > effects > power amp > speakers

I am really wanting to try this set up some time. Would love to hear from others on this.


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## greco (Jul 15, 2007)

Do you have a schematic for....or a picture of.....or a link to.... the "Dummy Load Box" ?

This is a new concept to me.....however, I don't often wander very far from my cave these days....LOL

Cheers

Dave


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## Fader (Mar 10, 2009)

I think he would be talkin' 'bout a power attenuator like a Power Soak, Marshall Power Brake or THD Hotplate or something.


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## greco (Jul 15, 2007)

Fader said:


> I think he would be talkin' 'bout a power attenuator like a Power Soak, Marshall Power Brake or THD Hotplate or something.


Gotcha...thanks. 

Cheers

Dave


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## mhammer (Nov 30, 2007)

There are two general kinds.

One is a box that simply absorbs the output power of the amp by providing a load comparable to what the transformer expects to see. You can often accomplish that by going to your local industrial electronics outlet and scoring yourself some suitable power resistors.

Of course, loudspeakers are not fixed resistors. The characteristics are dynamically changing as the voice coil moves around. So, it should be no surprise that there is another broad category of box that attempts to mimic not only the absolute resistive properties of a loudspeaker, but the dynamic properties as well. These are more complicated....and expensive.

Another approach is taken by use of a post-transformer "slave" output. The intent here is to include whatever it is that an output transformer (in a tube amp) does, and use that as a signal source for further processing or amplification. Note that this leaves the amp's speakers still wired and functioning. Thik of it as the equivalent of mic-ing juuuuuuuust ahead of the speakers.


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## prodigal_son (Apr 23, 2009)

Here is a link to one item I have read about these:

Exploring Edward Van Halen's Early Legendary "Brown Sound"

Please do not read this as me being a Van Halen wanna be...


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## greco (Jul 15, 2007)

This is copied from the above link:

*"The second way Edward controlled his overall output volume was that he would use a dummy load box after the Marshall head, in effect making the Marshall a preamp for the entire system. The output of the load box would then run through his effects which would then be sent to the input stage of a power amplifier (most often an H & H V800 MOS-FET model according to the September 1986 issue of Guitar World). The speaker output of his Marshall was set at 8 ohms and the dummy load box resistance was set to 20 ohms to help ease the strain of the amplifier being run at full volume.

The benefit of the dummy load configuration was not simply to control the volume levels (Edward liked things loud!), but also to enable his time-based effects to work and sound well within the signal chain. Anyone who has tried to run a flanger or a delay in front of a fully cranked Marshall will realize that the effects just don’t work well. In the case of the flanger, this is because the power tube distortion will compress and distort the flanger’s sweep and dynamics will be eliminated. For a delay run in this fashion, the repeats of a delay will be amplified and compressed also and not sound like a true echo. When Edward ran the Echoplex in between the Marshall and the H & H power amp, it also made the Echoplex much less noisy in addition to simply producing a better tone."*

I have built a dummy load using power resistors, to absorb the power from the OT, as mhammer mentioned. 
It was my understanding that the output from only power resistor(s) would totally destroy one's tone.

I'm interested to learn more about the complicated and expensive "dynamic boxes" that mhammer describes.

Cheers

Dave


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## Guest (Aug 6, 2010)

To do what Van Halen did there are a couple of off-the-shelf options:

An Ultimate Attenuator: Ultimate Attenuator
A Palmer PDI-03 or PGA-04: JAMS Audio - Nashville, TN - JAMS Audio - Nashville, TN

I've used a PGA-04 and it's great. In addition to acting as a reactive, dummy load you can do speaker simulation with it. So you can go direct to FoH or you can run it in to a power amp and then in to a traditional guitar cab if you like. It is a very nice thing to be able to run your power amps output into effects instead of using a post-preamp, pre-power amp effects loop.


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