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Jolly's Tube Amp in a Tele Build


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Hello everybody! Just for some quick background this will be my 4th build. They've all been a little less than straightforward and range from a 70's era Martin acoustic kit to an entirely 3D printed Les Paul Jr.

Anyway onto the concept for this build. I've seen several guitars throughout the years with built in amps but they've all been low quality or gimmicky. That being said, if you look past the shortfall of what's commercially available the concept seems solid. Theoretically speaking there's a lot of common ground between what makes a good solid guitar body and speaker cab. I'm in the tube amps are better camp so to hedge my bet and fulfill another long time project itch I'm going to try and package a tube amp in a Telecaster.

I wanted to keep each element as simple as possible since I'm trying to mix a lot of things. I've been brainstorming ideas for the last few weeks and settled on drawing inspiration from an Esquire for the guitar half and a "champ" for the amp half. The body is going to be wrapped in tweed and the pickguard will be black grill cloth. The amp is going to use space-charged tubes; near the end of the vacuum tube era they made a few tubes designed specifically for car radios where everything ran off of 12 volts. Specifically I'm going to use a 12U7 pre amp tube and 12K5 power tube. It is going to be powered with a cordless drill battery, I did a quick breadboard test and got a little over an hour of play time with a 1.5Ah battery. It was pretty noisy being on a breadboard and all but I think it's got potential to sound great! Theoretically you can coax ~¼ watt out of the 12K5

In an attempt to set myself up to actually finish this I've ordered pretty much everything I need. Should be a fun winter project. Since I've got most of the parts already here are the tentative specs:

  • Pine Body With ¼' Plywood Top and Back
  • Fender Standard Series Telecaster Neck (Left Handed, Maple Board)
  • McNelly A5 Signature Bridge Pickup
  • Kluson Tuners
  • All Parts Bridge (surprisingly hard to find left handed options)
  • Quam 4" Moisture Resistant Speaker
  • 1/4 Watt 12U7 & 12K5 Tube Amp (probably point to point but haven't got that far yet)

Here's a pile of parts picture and a rough idea of what I think the layout will be.

[img]https://live.staticflickr.com/65535/50557119662_10d116159d_b.jpg[/img]

[img]https://live.staticflickr.com/65535/50556990956_92e6af4914_b.jpg[/img]

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I didn't order a battery online because nobody had good dimensions and I wasn't sure exactly what I wanted. After getting a feel for how much room there was to work with I ventured out to the home improvement store and ended up with these. They're 18V, 2Ah from good ol' uncle Bosch. The tubes are rated for up to 30V on the plates so this will let me run them a little hotter. Really it was just the only battery I found that was thin enough, ~1.5" plus the latch. 

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27 minutes ago, curtisa said:

Heavy, man :thumb:

 

 

 

 

Seriously though - how heavy? ;)

I tried to keep weight in mind when sourcing everything but she's going to be a brute. My rough goal is to keep it in the Les Paul range, we'll see how that goes. 😂

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@Jolly, good ol' unca Bosch sure is a safe bet for longevity - or any other widespread brand for that matter. I've got a bunch of various battery operated tools bought at different times from different shops and they work just fine for my pretty little needs. Needless to say that the batteries aren't interchangeable...

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Not sure on battery life yet. I got about an hour with a smaller battery. My eyeball guess is 2-3 hours but I haven't done the real math yet. I'm planning to leave a big chunk of the back open and cross the heat bridge if it becomes a problem. 

Did a little bit of breadboarding this morning with the new battery. Honestly it sounded like garbage but I got sound though so we're on the right track. I was just piecing old schematics together so I'm hoping for better results once I start coherently designing it.

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With a good idea of where all the components need to go I moved on to designing the body. Keeping manufacturability in mind I sketched out a few possible configurations and ended up moving this one into the digital world. I use Autodesk Fusion 360. I much prefer Inventor but its hard to argue with free. With the center set to generic pine and the top and back as generic plywood the model predicts the wood parts of the body at 2.75lb.  As an eyeball guess I don't imagine it straying far from there in real life. I couldn't help myself and weighed a box of parts, nothing neck related but everything that should go into the body; battery, transformer, bridge, switches, etc. That came out to 3.4lb for a total body weight just over 6lb. How does that compare to normal loaded tele body? What does a normal finished Tele weigh?

With a CAD model at my disposal I couldn't help but do a little rapid prototyping. The first picture shows the 3 separate parts from left to right; top, core, back. I think I'm going to end up making three templates, one for each part. That should get be most of the way to a finished body. 

The next picture has the top glued on to the core. For the real deal this is the stage where I'll wire the amp. There should be limited access to most of the electronics once its fully assembled but I'm also expecting some "test and tune" at this stage which will be much easier in the open. The scaling for the 3D prints came out a little weird and the top/back hung over the core a bit. To counter this on the final build I'm going to only have the profile on the core template and then use the core as the template for the attached top/back. It's hard to see on the 3D print but the CAD model has 2 holes near the top for locating pins of some kind. 

I have a pretty limited woodshop myself but I have plans to visit my parents this weekend and while I'm there plan to take advantage of their tools a bit. The last picture is of the pine I plan to use for the core. It was tucked up in the rafters of the garage since long before I moved into my house so it should be plenty dry/stable by now. There's a few different boards but they're all roughly 1 x 12 x long. All the wood is going to be covered in tweed so I'm going to layer and piece together a body blank with a big square hole in the middle.

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44 minutes ago, Jolly said:

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where did you source that foam?  looks pretty rigid and nice... have been trying to think of something to use for upcoming cnc prototyping activity and the best I could think was the pink insulation from lowes.  this looks like it takes a bit much better.

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6 minutes ago, Jolly said:

It's 3D printed PLA, no machining necessary. If you try out the pink foam you'll have to let me know how it goes!

3d printer - right on.  pretty cool stuff. 

yes, I'm going to hit the home depot/or lowes this weekend and see if I can find something around 2" thick and suitable.  fingers cross but I will def post my results either way.

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I received a shipment of Baltic Birch plywood! I got 1/4" for the top/back and 1/2" for any templates or fixturing I may need. I also have a sheet of 1/8" on backorder that I think will work well for the battery holder. Time to start laying things out.

I also built a slightly more polished amp prototype. I was having problems with a few connections on the breadboard and figured it was simple enough that I would just solder it together. It certainly needs some tweaking but the results were promising! It has all of the touch sensitivity and sweet asymmetric distortion of a fully cranked tube amp without the ear splitting volume. I tested it with both a 12" speaker cab and the 4" speaker sitting on the bench. The 4" speaker obviously moved a lot less air and was noticeably quieter but still should be plenty. The mass of the guitar and the speaker being properly mounted should give me a little more volume. I've also got to imagine this will throw off a little more acoustic volume than your average solid body.

With all of that considered my educated guesstimate is that I'll be able to get roughly acoustic guitar volume out of this. Should be perfect for an all in one practice rig.  

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Edited by Jolly
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  • 3 weeks later...

Well I finally got around to doing some actual woodwork! I ripped the pine in half and cleaned up the outside edges to give me about 5.5" wide boards, then planed them down to ~.625". I was originally going to layout the blank with a square internal opening at or close to finished size to avoid having to do much internal shaping. After further consideration I decided I didn't like where that put my glue joints and it was going to waste a lot of material. I shrunk the center hole and gained enough material for a second core blank. Just for fun I stacked everything up to get an idea of the finished layup. Between two layers of 1/4" plywood and two layers of 5/8" Pine the full blank comes in almost exactly at 1-3/4"

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I decided to use hide glue for this build because it could do double duty for the wood work and applying tweed. This was my first time using hide glue but it seemed to go okay! More on that when I unscrew the blanks tomorrow. I tried several different dry set ups but I wasn't getting anything that felt solid enough with the clamps I had. Since much of the outside and inside of the blank is just extra stock anyway I decided to screw it together. No wood is going to show on the finished product so even if a screw hole makes it past the profile I'll just fill it and move on.  I used the leftover glue to test out gluing on some tweed scraps. I've seen people recommend both putting the coating out and in so I figured I'd try both see what one holds best. I'll also probably use these to test out some finishing options when the time comes.

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I've made some major progress! After pulling all of the screws out of the core blank I screwed the plywood to the top and back. I put the screws in places that wouldn't be effected by cutting the inside "speaker cab" or the outside profile. This let me process the blank as one piece even though the top and back aren't glued on yet. I traced the outline on the top sheet of plywood and then started laying out all of the other features that needed to be cut. I worked off of print dimensions for most things but the pencil marks provided a much needed sanity check along the way. I cut a few small pieces out of the edges of the top plywood so I could clamp directly to the core and set it up in the mill. Shoutout to my Dad for letting me use his mill and for providing some much needed machining expertise. We oriented the penciled centerline and the back of the neck pocket as zeros so the profile would be in the right place and got to cutting. First step was drilling all of the holes; two through holes for locating dowel pins, the neck screw holes, and the bridge screw holes. Then the control cavity was milled to size and the pickup cavity roughed out. We were using a manual mill so the neck pocket isn't tapered yet but we cut a square pocket to the smaller dimension and put the correct radii at the wider dimension which should make it pretty easy to hand fit when the time comes. We also through cut the square parts of the outside profile near the neck. Finally we used a hole saw for the speaker hole finishing up all feature for the top. I was also planning on including a tube access hole just below the speaker hole but I didn't like how little material that left in that area so I opted out at the last minute.  

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Because we clamped directly to the core we were able to remove the top plywood without changing our setup. This allowed easy reference to the top features without additional layout along with improved accuracy between pieces. The first step was milling out the "speaker cab", stopping just short of the bottom plywood. This also included a battery slot and a shallow speaker clearance slot. Then two holes were cut using a hole saw to start the back slot. Some quick passes between them with an end mill finished up the mill work. 

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I then reattached the top with screws and dowel pins and rough cut the profile on the bandsaw. Finally I used a combination of disk and spindle sanders to finish the outside profile. I also cleaned up the pickup cavity with the spindle sander.

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