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Jolly's Tube Amp in a Tele Build


Jolly

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Thanks for the kind words everyone! I'm super excited with how well it's coming together.

I used the thickest binding router bit I had, set to a depth of approximately two layers of tweed plus some glue to add channels around the top and back of the core. This should let me hide all of my tweed edges, prevent them from soaking up extra shellac or glue, and help to keep all the fabric in place.

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I also trimmed the excess tweed from the back of both the top and back plates.

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I cut a long skinny piece of tweed to wrap the outside of the core. Using hide glue, I started with the strip centered at the neck pocket and wrapped it around both sides until it overlapped on the opposite side centerline. Once it dried I cut off the excess tweed, roughly flush with the top of the core, so I'd have a little bit left to tuck into the grove.

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Unfortunately the placement of the speaker and transformer are such that they had to be installed before gluing the top to the core. This will be easy to remedy if I ever build another, but for now I just put it together and pressed on. The amp wattage is well below the speakers rating so hopefully I never have to deal with replacing it!

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With those few components in place I glued the top to the core. I used Titebond II instead of hide glue as I'm not confident this joint will be perfectly flat and I wanted something a little more forgiving. I went around the outside with a putty knife to push the fabric into the groove and then taped it tight. I started with 5-6 widely spread pieces of tape to keep everything flat and then circled several more times, tucking and adding tape in any remaining gaps. Once I was happy with the outside I added a few clamps.

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How about with both the top and back joints?

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The back isn't glued on yet but I was fiddling with the neck and had to get a sneak preview of how it was all coming together. My original thinking stemmed from the similarities in physical construction between solid body guitars and amplifiers but I tried to capture that same spirit in the aesthetics as well. I'm obviously biased and hate to sound too surprised but its looking way better than I had hoped! Its hard to fully capture in pictures, but it has a certain vibe that's at least different than anything I've ever played.

On to why I was fiddling with the neck.

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When first installing the tuners I stripped basically all of the screws. It was fine for testing but as I get closer to finishing I figured it was time to deal with this.

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I'm not sure if I drilled my pilot holes way too small or if they were just super low quality screws, but they got very very stripped so I had to drill the heads off. This allowed me to remove the tuners and use a pair of vice grips to unscrew the remaining nubs. 

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While I had the hardware off I applied a ceramic coating to the neck. I have a buddy who runs a high end detail shop and he raves about them so when I stumbled across one for guitar I figured it was worth giving it a try. His advice was to make sure it was incredibly clean first so I used some alcohol to remove any oil that had built up from the little bit of play time. To actually apply this particular coating you just mist it on and immediately buff off.

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I've just started using this so I don't really have any experience on how well it works yet. In theory it causes moisture to bead up and run off along with providing some scratch resistance. My main plan is to use it on the body to give the shellac some moisture/alcohol resistance.

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2 hours ago, Jolly said:

its looking way better than I had hoped!

It's looking - umm... what's the superlative for killer?
Some wax/soap might help the screws go in without stripping.

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  • 3 weeks later...
On 2/13/2021 at 4:16 PM, Bizman62 said:

Some wax/soap might help the screws go in without stripping.

Thanks for the tip!!

 

On 2/15/2021 at 7:03 PM, ScottR said:

Every tuner set I've ever bought has cheap ass screws......

SR

I've been jumping through hoops to find some screws locally and avoid $10 in shipping for $3 in screws. I finally broke down and got StewMAX so hopefully those small things don't slow me down in the future. Flingers crossed the aftermarket screws are a little better!

For the last bit I've been struggling with getting the amp and battery packaging to work. It all fits but I've been having a hard time getting it to be solid and look clean. I've also cant leave well enough alone and have been fiddling with the amp circuit, trying different tubes, etc. I used resistors to drop the heater voltage and that worked but it got really hot, hotter than the tubes. The solution I came up with...

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I'm going to use the battery out of my cordless drill! I'm bummed about the sunk cost in the Bosch battery and that the drill has to share now but this solves a few problems. First, its a lot smaller so it will easily clear the pickup, the Bosch battery fit in place but had some clearance issues putting it in or out. Second, its 12 volts so my heater issue is gone.

I'm also going to give up on point to point wiring and build a small board off to the side. To clear the speaker and pickup the tubes have to be tucked up in pretty far and any amount of components behind them was cutting into that valuable space.

This is less relevant now but here's a few fun mock up pictures from before I made the battery switch.

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3 hours ago, Jolly said:

Some wax/soap might help the screws go in without stripping.

Just for the record it also helps drilling long stretches without squealing.

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I just got a box of odds and ends delivered!

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The list includes a 250k push pull pot, various wire, tuner screws, and pickguard screws.

I've been using the pickguard taped in place to protect the speaker in process. It will have to come off before I finish it but for now I figured it was worth solidly attaching.

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I got my final tube mounting situation figured out. I started by cutting a piece of plywood to the same depth as the cavity and drilled two holes for the sockets. Its basically the same as my test board but with a little more thought put into tube spacing and orientation.

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I wanted to get the tubes as high in the body as I could for clearance and heat. There's not enough room to fit components near the sockets with this layout so I'm going to run wires from the pins out to a board on the left.

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There should be plenty of room to change tubes through the back slot.

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Here's a close up of the circuit board. I still have a lot of wiring clean up to do but I'm getting close to having everything in its final place! I got about 5 minutes of playing on it and popped the fuse, pretty sure it was just some of the loose wiring that shorted and it shouldn't be hard to fix. I lost a little bit of volume going from 18 to 12 volts but also gained a little bit of clean headroom. I'll try and post another video once I get my wiring issues sorted out.

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This is really fun to play! Both the tone and volume control are pretty useful and can pull off some dramatic tone change. It's very responsive to how hard you play. It has some surprisingly nice clean tones and just gets past the edge of breaking up if you really hammer power chords. I'm going to put a fresh battery in to get a total play time, I'll record a demo at the same time. For now here's the schematic!

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Here's a couple of quick demos! It just my cellphone mic so go easy on the sound quality. I start both videos with the amp muted to get an idea of acoustic volume. Then I move to the raw channel and finally the tone channel. For these videos the volume and tone are on full.

Also, I made it through a full battery. Just over 2 hours of play time per charge!

 

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Very impressive.  That would certainly add a bit of 'zing' into an average acoustic open mic night :D

The bit that I am still enamoured with is that this isn't just an amp and speaker in a guitar...this is a VALVE amp.  And it sounds like one.  With some judicious tweaking of the volume levels, you will be able to get the classic 'clean to crunch'.

Love it :)

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On 3/24/2021 at 4:08 AM, Andyjr1515 said:

this isn't just an amp and speaker in a guitar...this is a VALVE amp

A little glass goes a long way. :rock 

Between changing batteries mid build and general troubleshooting I've probably 3D printed 5 or so revisions of battery holder at this point. In the scope of all I'm trying to fit in this build I thought this was going to be an easy after thought. Turns out it was a huge pain. I feel like there one of those tasks in every project. Anywhere here's how it turned out.

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I split it into 3 pieces so I could print everything in an orientation without supports. The mounts I made as 1 piece with supports turned out okay but were a little rougher and required a lot of cleanup in a hard to reach spot. I also added a cover so I could solder the batter tabs after the mount was in place.

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It just so happens that the back of a razor blade is about the right size to be a battery terminal. I broke off the majority of the blade itself but the little bit that was left worked well to secure it to the plastic. As a fun bonus the guitar now has a made in the USA label.

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Even after several part revisions it was still a major undertaking to get all of the wires hidden in the channel. I eventually got it though, pulled it out just a little with all of the wires still in place, and dripped in super glue. Before I started assembling the battery holder I hot glued the circuit board in place.

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I cut the power leads to length and then soldered them to the terminals

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Finally I glued the cover on to hide the solder joints and covered the entire battery holder with a little bit of wax.

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This should be about what my final wiring looks like, minus the not yet built boost circuit. Its a little less neat than I was originally hoping for but I'm going to cover it and never think about it again!

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It's currently hotwired in but I got the circuit for the final switch position finished! I used the clean boost schematic linked below with 22uf caps instead of 10uf because its what I had lying around. I also have it on a separate 9v battery currently. Anyone see a reason I couldn't just run this from 12V? Worst case scenario I think I could drop the voltage to it by adjusting a resistor or two.

http://effectslayouts.blogspot.com/2014/11/jfet-boost.html

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The guitar is out of commission right now because I need shorter screws to reattach the bridge. Like I said the boost is just wired in temporarily right now but here's a quick demo of the amp and boost using an auxiliary guitar.

I don't want to speculate on how its going to sound as a total package yet but... I think the extra gain is the icing on top this needed! With the boost engaged the single note leads have useful distortion now and the chords/multi note lines have a light lo-fi fuzz sound.

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23 minutes ago, Jolly said:

Anyone see a reason I couldn't just run this from 12V? Worst case scenario I think I could drop the voltage to it by adjusting a resistor or two.

It will work fine on 12V. May have slightly different gain characteristics compared to 9V, but will still operate the same way. The 22k resistor may need to be changed in order to get it to bias properly, but that's also the case with it running at 9V too.

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  • 3 weeks later...

Life has been busy the last little bit but I've finally made some more progress on this. I ran into a strange feedback issues when I wired the solid state boost from the last video into this guitar. After a little to much poking at it, I let the magic smoke out and had to start over. Unfortunately the new circuit had the same feedback. It wasn't too much gain feedback, it was a little more static noise type feedback. After some additional investigative poking around I added some capacitance between the output and ground and it cleared up. This wasn't my first move though so by the time I was done my board got pretty messy.


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That being said.... oh man is it cool now.

 

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I figured it was past time to put the string trees on. Notice anything wrong?

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It's a bummer of a little mistake to make this late in the build but oh well. Once I fixed it my string break angles all came out pretty consistent so that's a plus. I think the extra hole will disappear pretty well if I fill it but I might just leave it as some "prototype charm".

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I attached the boost circuit board to the bottom corner underneath the speaker and signed the back.

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I didn't get any in process pictures but I glued the back on with basically the same steps as the front. The major exception being I used hot hide glue for the back, If anything ever needs to be serviced the back should be relatively easy to remove.

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12 hours ago, Jolly said:

Notice anything wrong?

My media reading skills need some improving, I didn't see anything wrong in the first picture!

12 hours ago, Jolly said:

the extra hole will disappear pretty well if I fill it but I might just leave it as some "prototype charm".

Don't leave holes, put a black side dot marker there! Or even better, something decorative like a faceted jewel that is just a tad proud of the surface - a black crystal stud earring!

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