Completed JohnH Attenuators?

[LAPickGuitar]

I found the @JohnH attenuator thread after buying a cheap tube amp (Harley Benton) and then starting to learn about tube amps. Realizing that I needed an attenuator and reading the reviews of commercially available models led me here. I'm committed to building an amp and this gave me the chance to polish my dormant soldering skills from back in the day when I built oscilloscopes for Tektronix. Here's my basic M2...

I have heat sinks ready to mount, but I want to see how hot the enclosure gets first. Ran the amp through it for the first time tonight. Works perfectly. Fun little project! Thanks @JohnH !!

 

[kenjib]

I have made one of these suckers for my 1979 JMP 2023(100 watt) Marshall. It does run pretty hot when I am diming the amp but I haven't had any actual problems yet. Maybe I will eventually have to replace the fan with something stronger but this one is dead silent, which is pretty cool. I have owned this amp for around 30 years and almost never turned it up past like 2 1/2. It is so cool to finally hear what the amp is actually supposed to sound like after 30 years. It sounds even better when I am also running through my Roland RE-101 Space Echo! It is amazing and I have found a new love of playing guitar. Thank you JohnH!!!!!!

 

[dtier]

Another completed M2 50 watt 16 ohm build. My first. It was a fair amount of work, as I suspected, but worth it. I used the suggested Hammond box and general lay out. I'm gonna have to build one for my Fenders as well. Hats of to @JohnH for the design and engineering. The response and tone balance though the steps is remarkable. Thanks as well to @Gene Ballzz for his knowledgeable contributions to this subject. I will post some observations about my build on the design and testing thread as well.

 

[JohnH]

hi @dtier , that looks great! I like the retro labels too. That might be my favourite way of doing them short of something much more complex. But yours are particularly regular and neat. What was the tool for making them? Im also enjoying the stand-off base for the coil.

 

[JohnH]

hi @kenjib , yours looks like its the business, and the fan looks effective, good size and there's plenty of space inside, even at 100W. I'm sure it heats up still. If you can touch it for a couple of seconds near R1, then its likely not more than 60C or 65C, which is all fine in that case. How does the heat feel based on that approximate finger test? (I have a basic laser/IR thermometer for testing like that, a really neat gadget but not part of most workshops!)

The fan drilling pattern is a work of art!

 

[dtier]

hi @dtier , that looks great! I like the retro labels too. That might be my favourite way of doing them short of something much more complex. But yours are particularly regular and neat. What was the tool for making them? Im also enjoying the stand-off base for the coil.

Thanks! I used an old DYMO embossing labeler I have had for decades. You mentioned it earlier and reminded me that I had one. I like the retro look as well. Unfortunately the labels don't want to adhere well to the rough finish on the box so unless I find a way to adhere them better I will have to use something else. The coil base is a left over piece of turret board.

 

[stickyfinger]

I found the @JohnH attenuator thread after buying a cheap tube amp (Harley Benton) and then starting to learn about tube amps. Realizing that I needed an attenuator and reading the reviews of commercially available models led me here. I'm committed to building an amp and this gave me the chance to polish my dormant soldering skills from back in the day when I built oscilloscopes for Tektronix. Here's my basic M2...View attachment 145906View attachment 145907View attachment 145908View attachment 145909

I have heat sinks ready to mount, but I want to see how hot the enclosure gets first. Ran the amp through it for the first time tonight. Works perfectly. Fun little project! Thanks @JohnH !!

Drill holes top and bottom! It is crucial IMO. Event though the amp is 15 watts keeping things cool is vital for longevity of components and amp. Love the labeling is it water slide decals?

 

[kenjib]

hi @kenjib , yours looks like its the business, and the fan looks effective, good size and there's plenty of space inside, even at 100W. I'm sure it heats up still. If you can touch it for a couple of seconds near R1, then its likely not more than 60C or 65C, which is all fine in that case. How does the heat feel based on that approximate finger test? (I have a basic laser/IR thermometer for testing like that, a really neat gadget but not part of most workshops!)

The fan drilling pattern is a work of art!

I can touch it for a few seconds so I guess maybe it must be okay? I'm glad to know that it won't be a problem then but I will keep an eye on it. I did find, however, that I really do need to run the fan at a full 12 volts. It was not cutting it at 9v. It is definitely moving less air than I expected. I just hope my kids don't forget to turn on the fan power before using the amp, though I think it's totally fine without the fan running for edge of break-up levels @5-6 though. I think it just gets problematic running higher than that.

Thanks re: the drilling pattern! I ordered a compass for the layout and was then sitting on the front porch drilling for several hours. I don't think I would want to do it again, so if any of my friends want me to make them one they will be doing their own drilling!

 

[LAPickGuitar]

Drill holes top and bottom! It is crucial IMO. Event though the amp is 15 watts keeping things cool is vital for longevity of components and amp. Love the labeling is it water slide decals?

Yes, waterslide. I bought a pack for my Tele build headstock, but it gave me 1000 times what I needed for that project. The resistors are well bonded to the top surface. No particular warmth yet, and I haven't needed to mount my heat sinks. But I haven't been able to play for long, so I'll keep monitoring.

 

[jfromel]

I went a different direction with this one..... posted details of the build in the SA thread.

 

[Marcomel79]

Finished this 8ohm attenuator for a friend last night. This is my second JohnH attenuator and as expected, works like a charm!

 

[Marcomel79]

I followed @Gene Ballzz layout for this build, and added a 4ohm out as well. The enclosure is a Hammond 1590DE, slightly bigger than the 1590D i used for my original build. Here are somo photos side by side

 

[PelliX]

Finished this 8ohm attenuator for a friend last night. This is my second JohnH attenuator and as expected, works like a charm!
View attachment 150302View attachment 150301View attachment 150303View attachment 150304View attachment 150306View attachment 150307View attachment 150308View attachment 150309

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I like the coil!

 

[zinnat]

Here is my first JohnH attenuator build, M2 8ohm with line out:



I'm really impressed by how naturally it behaves at all attenuation settings, and I must also say that the basic -7dB attenuation is already enough to be able to enjoy fully my SV20H at home in most situations.

Thank you JohnH for your amazing work, you are donating thousands of smiles on the faces of people around the world

I thought the reactive attenuator would make my master volume pot in the FX loop of the SV20H unnecessary, but actually I'm finding out that I like to have both the attenuator and the master volume engaged. I set the desired speaker loudness with the attenuator settings, and I use the master volume in the FX loop to dial in the desired amount of PI/power tube distortion, while keeping the amp controls set in my favorite spots.

With the SV20H and lower powered amps (Princeton, Champ), the resistors get barely lukewarm. So for my usage (I never dime the SV20H anyhow for blues and classic rock), heat management is not an issue at all. I used thermal epoxy to glue the resistors, and I don't feel even the need to drill the bottom and top of the aluminum case at the moment.

I'm now waiting for an IR cab simulator pedal in the mail: I have hopes that with this, the JohnH attenuator might also solve my long standing issue of getting a pleasurable tone through my headphones for late night practice.

Really amazing, thank you so much JohnH!

 

[diego_cl]

I've built three units so far and I think I'm finally done with it:

M2 50 watts 16 ohms
M2 50 watts 8 ohms
M2 100 watts 16 ohms

Thank you @JohnH for this incredible circuit. I had been dreaming of having an attenuator since the 2000s.

 

[JohnH]

Thanks @diego_cl , that's a great set of builds and thanks for showing us!

 

[PelliX]

I've built three units so far and I think I'm finally done with it:

M2 50 watts 16 ohms
M2 50 watts 8 ohms
M2 100 watts 16 ohms

Thank you @JohnH for this incredible circuit. I had been dreaming of having an attenuator since the 2000s.

Noice, I like the third one! Is that a Sony MDS-JE530 deck in the background?

 

[diego_cl]

Noice, I like the third one! Is that a Sony MDS-JE530 deck in the background?

Holy sh*t, how did you know that!! Yes!

Shortly after learning how to play guitar in the late 90s, we got this wonderful device that allowed us to transpose Eb tuned songs into E standard without retuning the guitar, thanks to the pitch control. The "A-B repeat" was very useful for learning difficult solos. So many GNR songs were played through this thing. The next best thing to GuitarPro (at that time).

 

[PelliX]

Holy sh*t, how did you know that!! Yes!

Hehe, got a couple myself that I used a lot. Also in part like you did; though I tended to record a rhythm part, cut that to an individual track and set it to single repeat. A-B has a delay on those units, which repeat doesn't. I also have a forerunner of those decks which has a much faster A-B function, but it's not seamless.

 

[Jumping Jim]

I inherited Dad’s Vox Berkeley Super Reverb (model V-8) a couple years ago. It’s an all-tube amp based on the AC15. The thing is that I just never use this amp since it’s just too loud in my house. I recently started looking at commercial attenuators which varied between mediocre and super expensive… and delightfully found myself here.

The Berkeley outputs about 17 watts into 8 ohms, so I made the standard M2 and installed it into empty space in the right side of the head. The components are on a 1/8” thick aluminum plate and barely get warm. The control panel clamps in place and the attenuator just plugs in. There are no changes to the amp, and no soldering to install or remove the attenuator. Photos should be somewhere in the post.

Using the M2 has been wonderful. It’s completely unlocked the amp, and I’m having a ball playing it. It’s just a great feeling playing this old amp and really getting to put it through its paces.

Let me finish by thanking John for his brilliant success with this attenuator project. And more thanks to him, Gene, and others for answering tons of questions. You guys are great.