Reactive attenuator??

davebolden44 · Post by **davebolden44** » Tue May 10, 2022 12:35 am

This question might be played to death but I will ask it anyway. I am looking for experience, insight, anything about a reactive load attenuator. I have built a couple out of Lpads and they work fine but definitely make things darker. I want to eventually build a 50 watt hiwatt clone and would like to also be able to drive it and retain its sonic character at lower volumes. Tale as old as time right?? So tell me guys am I nuts? Any luck in this department?

BrownIsound · Post by **BrownIsound** » Tue May 10, 2022 2:11 am

There’s a long post on the Marshall forum on this, with a circuit many people having made and liked, with several improvements. I have not yet made one, but it is on my list of things I want to do.
https://www.marshallforum.com/threads/s ... ing.98285/

cys · Post by **cys** » Tue May 10, 2022 2:23 am

The last part of your post made me want to respond that I have had luck, but with fluxtone speakers. Sorry, I can't help with reactive attenuators.

aceofbones · Post by **aceofbones** » Tue May 10, 2022 3:21 am

I have built the one linked above (the M2 version) and use it with my Trainwreck Express clone. It works unbelievably well and was inexpensive to build.

There are many, many successful builds of it and everyone seems to speak highly of it. I'm sure others from that thread will chime in here. Geneballz from the thread is a regular on here, I think his username might be theballz here, and is a major contributor and proponent of it and has built multiple of them if I'm not mistaken.

For the cost of it, it's silly not to try building one.

pullshocks · Post by **pullshocks** » Tue May 10, 2022 1:56 pm

Another M2 builder chiming in.
Never used an attenuator of any kind before so didn't really know what to expect. Playing at 60 dB SPL is a different sensory experience than playing at 85-90 dB SPL. Once you get past that and focus on what you're playing, it's actually pretty cool.
Well worth it in my opinion, even with the 4-15 watt amps I have.

Completed attenuator 700.jpg

martin manning · Post by **martin manning** » Tue May 10, 2022 2:39 pm

That thread on the Marshall forum is massive, been through it once a while ago. I see member Gene (the ballzz on TAG, I believe) has an 8-ohm version that he's happy with, and I have someone asking about an attenuator for studio use. Anybody know where the schematic for that might be? Is it the M2 circuit with values for 8 ohms at the top of the thread? Gene?

aceofbones · Post by **aceofbones** » Tue May 10, 2022 4:13 pm

martin manning wrote: ↑Tue May 10, 2022 2:39 pm That thread on the Marshall forum is massive, been through it once a while ago. I see member Gene (the ballzz on TAG, I believe) has an 8-ohm version that he's happy with, and I have someone asking about an attenuator for studio use. Anybody know where the schematic for that might be? Is it the M2 circuit with values for 8 ohms at the top of the thread? Gene?

Hey Martin, the very first post in that thread gets updated occasionally. The drawing labeled M2 March 2021 is the most up to date, I believe. There are the odd alternative versions people ask for and a schematic gets tossed up, deep in the thread, but unless you're in there following along you'll pretty much never find them.

Here is what I believe is the latest version. I've built the 8 ohm version listed here, and it works great.

M2-schematic.gif

edit..
I should note this is for a 50W amp or less. If you've got anything larger you need to double all resistor values to make the 100W version.

martin manning · Post by **martin manning** » Tue May 10, 2022 4:52 pm

Thanks, Ace. I've been looking back through the thread. Clicking through the images I found this, which looks like the same circuit with a nice layout diagram.

aceofbones · Post by **aceofbones** » Tue May 10, 2022 4:59 pm

Oh very good. That must be the layout Gene did. JohnH was hesitant to put out a layout that showed the wiring. He said it was kind of the entrance exam, if you couldn't read the schematic you shouldn't build the attenuator. I think after 120 pages or so, it was finally okayed to show the world how to wire it up, haha.

aceofbones · Post by **aceofbones** » Tue May 10, 2022 5:02 pm

This is my 8 Ohm 50W M2 build.

martin manning · Post by **martin manning** » Tue May 10, 2022 5:06 pm

Heard that line of thinking before ;^) Making a nice neat layout takes some time and thought as well as schematic reading ability, and then some fab skills to make it real. Yours looks great!

pullshocks · Post by **pullshocks** » Tue May 10, 2022 5:14 pm

aceofbones wrote: ↑Tue May 10, 2022 5:02 pm This is my 8 Ohm 50W M2 build.

Nice!
Wish that layout was around when I built mine....
Note-- I reduced the ratings of some resistors since I will be using only with 4-15 watt amps

Attenuator guts 700.jpg

aceofbones · Post by **aceofbones** » Tue May 10, 2022 5:45 pm

martin manning wrote: ↑Tue May 10, 2022 5:06 pm Heard that line of thinking before ;^) Making a nice neat layout takes some time and thought as well as schematic reading ability, and then some fab skills to make it real. Yours looks great!

Thanks, Martin.

I can play pretty loud at home, but still not loud enough to let an Express unleash in anger, so this has been great to knock it down a hair and open it up.

@pullshocks That looks great as well. I like the riser for the inductor coil. That wasn't a thing in the thread when I built mine, but I see now it is recommended to space it up some from the case.

davebolden44 · Post by **davebolden44** » Tue May 10, 2022 8:43 pm

This is excellent information and exactly what I was looking for. Thanks guys, I cant wait to get started....

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