Completed JohnH Attenuators?

[Gene Ballzz]

Hey Fine Folks,
The Simple Attenuator thread has become so lengthy that it is difficult to ascertain how many successfully completed builds there are of the fantastic @JohnH attenuator design. I'm starting this thread with the intention of showcasing all of these great builds.

It is my sincerest request that only those with completed units reply here! I also request that any and all questions regarding these units and details surrounding them still get directed to the main

"Simple Attenuators - Design And Testing" thread, located here:

https://www.marshallforum.com/threads/simple-attenuators-design-and-testing.98285/

Of course, any likes or compliments are always welcome here!

I'll prime the pump (so to speak) with descriptions and pics of my two completed endeavors:

My first iteration of a 16 ohm M-Lite. The pics are of the earliest version, with an extra -7db stage in place of the -14db stage and no -3.5db stage. It has since been updated, but no current pics.




This next one is another 16 ohm M-Lite with a different layout, full bypass switch and a parallel option included by simply having two input jacks in parallel. You simply plug the speaker into the other input jack, set your amp to 8 ohms and set the attenuator to maximum atteuation for an overall -3.5db attenuation. It should be noted that the two "janky" stainless bolts holding the coils have since been replaced with nylon bolts, on BOTH units!



Given @JohnH advancements in design, I strongly recommend the M2 version over this (what I consider to be almost obsolete) M-Lite design, even though the M-Lite works just as well!

Thanks Folks!
Gene

 

[Guitar-Rocker]

Ok, I'll Bite. Here is mine, a M-Lite with bypass

 

[Marcomel79]

Here is my 16 Ohm version of the M2. Hope to see many more, there were some very nice ones on the original thread.

 

[matttornado]

Here's my 16 ohm build for my 100 watt superlead.
I built this way back shortly after @JohnH started the thread. I may re-build it into a better enclosure someday for portabilty as this one is a little flimsy but is still OK for now.

 

[Marcomel79]

Here's my 16 ohm build for my 100 watt superlead.
I built this way back shortly after @JohnH started the thread. I may re-build it into a better enclosure someday for portabilty as this one is a little flimsy but is still OK for now.

View attachment 101519 View attachment 101520 View attachment 101521

Looks awesome, and that 200W resistor is a beast!!

 

[donwagar]

I built the 16 ohm M2 for my SV20C, for practices and gigs. I left the -14dB stage out, but added a -3.5dB footswitch.

 

[matttornado]

Looks awesome, and that 200W resistor is a beast!!

thanks! yes it is!

 

[Barnsley Boy]

I built the 16 ohm M2 for my SV20C, for practices and gigs. I left the -14dB stage out, but added a -3.5dB footswitch.

The independent footswitch is a cracking idea! Definitely a contender for a future build. Did you mount the resistors in the footswitch enclosure as opposed to just having it as a switching unit?

 

[donwagar]

The independent footswitch is a cracking idea! Definitely a contender for a future build. Did you mount the resistors in the footswitch enclosure as opposed to just having it as a switching unit?

Yes, the resistors are in the footswitch. JohnH gave me the schematic for it, I'm not sure if it's posted in the main thread or if he sent it to me by PM. I did mount an LED but the pic I took was before I did that. It works great for a solo boost - I don't use any pedals with the SV20C.

 

[rallye440]

Here's my version of M2 build for 100W amps. I had to add a fan later because it got really hot, so I took one off from an old PC laying around. The power is taken from incoming signal so there's no need for external power adaptor. Works perfectly. I also own a Torpedo Captor X and Boss Waza TAE. This is just as good as those commercial devices. Thank you John for a great design!

 

[JohnH]

hi @rallye440 , that looks great!. It would be very helpful if you could put up a diagram on the main thread, of your fan power circuit with parts etc, plus any more info on the fan.

 

[rallye440]

hi @rallye440 , that looks great!. It would be very helpful if you could put up a diagram on the main thread, of your fan power circuit with parts etc, plus any more info on the fan.

Well I add the schem here. I just "borrowed" the fan circuit from the Captor. I used UF5408 diodes and 33,3R as in the schem (3x100R in parallel) for the 12V processor cooling fan. There is also an option to add a switch for two fan speeds because the fan I found has low/hi speed power feed leads. It could be useful to be able to adjust the spinning speed depending how much voltage comes in.

 

[aceofbones]

Here is my M2 50W 8ohm. I use it with Trainwreck Express clone I built. The Express is in the 36 Watt range. It is an insanely loud beast.
This is a straight forward M2 build without the 3rd output. The case came with the side vents, I drilled the top vent holes.

 

[Marcomel79]

Here is my M2 50W 8ohm. I use it with Trainwreck Express clone I built. The Express is in the 36 Watt range. It is an insanely loud beast.
This is a straight forward M2 build without the 3rd output. The case came with the side vents, I drilled the top vent holes.
View attachment 101780

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View attachment 101782

Looks really good!

 

[Barnsley Boy]

Here is my M2 50W 8ohm. I use it with Trainwreck Express clone I built. The Express is in the 36 Watt range. It is an insanely loud beast.
This is a straight forward M2 build without the 3rd output. The case came with the side vents, I drilled the top vent holes.
View attachment 101780

View attachment 101781

View attachment 101782

I'm in love with that case Ace! Where did you get it from? Looks expensive.

 

[Gene Ballzz]

Eight units and counting!
Keep 'Em Comin'
Gene

 

[Barnsley Boy]

Introducing DEFCON 1.... AKA "The Football" in light of what's happening on the borders of Ukraine, you can see why I have called it that!

A bit of additional spaghetti associated with the -28db stage:




Chunkier switches, which have worked out really well with the spade connectors. They are a tight fit, and made it a lot easier to do the connections. Admittedly the enclosure size has allowed me to use these, but worth investigating.




Hidden within that heat shrink tube is resistor RC (see attenuator build post page 120)




Temperature sensor loose laid on R1 - let's see how hot this baby really gets!



I saw these missile launch switch covers and had to have them!





Primed and ready to launch!




On the basis that when I turn up my amp World War 3 usually breaks out in the household, I have wired the switches so that they are at maximum attenuation when down. To wreak havoc and blow the windows out, you have to flip up the spring loaded covers and flip them up.

I still need to drill the vent holes in the top, I'm trying to come up with a suitable "cold war" pattern. Just for experimental purposes I have installed the solid lid and will CAUTIOUSLY test without ventilation to see how good the temperature sensor is.

PUKKA!!!!!!

 

[JohnH]

hi @Barnsley Boy , that looks great! I love the temperature sensor and the missile switches. I reckon that you had a full bypass feature, it should be engageded by two key operated switches, one controlled by your wife, after you both tap in the required codes.

 

[BlueX]

I saw these missile launch switch covers and had to have them!

Temperature sensor loose laid on R1 - let's see how hot this baby really gets!

Really cool switches!

I've been thinking about temperature sensor connected to LED's in blue, yellow, and red, connected so that they light up in turn as the temperature rises. Once the red lights up, it's time to take a brake from playing.

 

[Barnsley Boy]

I've been thinking about temperature sensor connected to LED's in blue, yellow, and red, connected so that the light up in turn as the temperature rises. Once the red lights up, it's time to take a brake from playing.

If you work out how to do this, let us know. That is somthing that I would definitely be interested in for my next build. I'm thinking bi-metalic strip switches (if there is such a thing), with increasing gap between contacts - perhaps fixed to R1. As they all heat up, the first one has less distance to flex to make a contact with an LED circuit, so green/ blue LED lights. The next one heats up even more, yellow LED lights, number 3 reaches critical temperature ....... core meltdown etc. etc.