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Discussion in 'DIY Effects Forum' started by BDON67, Sep 5, 2019.
Seems like a simple enough. Heat sink.. power resistors..
Hell...all you need is a 100 watt 8 ohm L-pad, a box, and 2 jacks.
And yes...I built one.
Yeah, a very simple one when I wanted tobuse the Fender Greta silently to record via the line out.
I just soldered a 10W, 8 ohm resistor to a plug and plugged it in to the speaker out. Worked like a charm.
Here's an example of what Fezz was talking about: https://www.parts-express.com/speaker-l-pad-attenuator-100w-mono-1-shaft-8-ohm--260-265
The reviews seem to indicate that it's not good for a steady 100 watts though. What's the output of the amp you're going to use it with?
I did this, except I added it to the speaker wire instead of adding jacks.
You could use a pair of resistors if you only want one specific amount of attenuation.
I use my 100w L-pad on a 75w tube amp. No issues, but it does get hot.
Tube amps are often rated based on clean output, not max output. So you would want to use resistors or L-pad rated for more than the amp's rating if you're going to crank the amp. Which is the whole point of an attenuator.
Oh cool! That's easier than I thought Thanks... i was thinking I would need a heat sink too? I'm planning something for my Super Reverb. 2ohms.. i can make a fixed -6dB something like this with 20W power resistors
That would work fine, but you might be surprised at how loud it still is. 6 to 10 dB quieter is usually considered to be what most people describe as "about half as loud".
You could always make two of them and use either one or both in series. I used to do that with my 50 watt '70s Peavey 212 Classic.
I used the 100 watt L-Pad with a Deluxe. And a Deluxe Reverb. And Princeton Reverb. Plenty of room to dissipate some heat. You want the box to be vented. LOL
I thought the Super Reverb was rated more like 40w, I think it does have a 2 ohm load. I'd suggest using resistors rated at least 50w. You don't want them to melt or catch fire.
Or buy a 2 ohm L-pad rated to 100w, and you'll have it adjustable AND you'll have plenty of "fudge factor" to keep it from overheating.
Great thanks for all the advice!...I like the idea the -6dB circuit.. wont require special odd value resistors.. a linking two or three in series will allow for lower power resistors and get me down to about 5W to 1W.. or a little higher on my 40W super reverb.. i'll make it good .. with a decent heat sink
Yeah, if your amp has only the 2 ohm output, you'll want something other than the 8-ohm L-pad I posted the link to. But I think you knew that already.
The fist one in line will get 3/4 of the amp's power and send 1/4 to the next one, as it would have with a speaker connected to it, so of course it would have to be as you had planned. The next one in line could have smaller resistors.
Why make them? They're lying around my work like candy. People toss them out regularly as well when they get old and oxidized.
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Good point! So i will definitely need to use minimum 25Watt on input stage. Thanks
The first one in line will see 100% of the amp's output power, which may be more than the amp's clean rated power if the amp is turned all the way up. I personally would spring for 100w rated resistors for the first one. Second stage will see half that so it would be perfectly safe to use 25w resistors, third stage will see half THAT and would be fine with 12.5w (if such a thing exists), and so on. It would work, but you have to remember to turn the resistors on and off in the right order.
As you look to get into this, remember that a 100w rated L-pad only costs about $10.
He showed a 6 dB attenuator. The circuit sends 1/4 of the input power to the speaker, so it dissipates only 3/4 of the amp's power. If you put a second similar attenuator where the speaker would go, that one would see that same 1/4 of the amp's power, and send 1/4 of that to the speaker. At that point the speaker would see 1/16 of the amp's power, 12 dB down from the amp's output.
I stay away from "If your work fails, the amp blows up" projects
I bought one for £35 then seen this video.
I tried to make one out of a light dimmer once....forget about it.