Jolly

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.  

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.

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.

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.

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.

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

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

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!

That's a sweet guitar! Nice website too

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!

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!

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.

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.

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.

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

I just got a box of odds and ends delivered!

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.

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...

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.

How about with both the top and back joints?

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.

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.

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. 

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.

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.

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.

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!

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.

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.

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

For the outside profile I basically repeated the same steps, however I traced the outline ~1/4" out from the plywood and started my perpendicular cuts from there. With the outside edges being visible on the final product I wanted to try and maintain a consistent tweed pattern. I had to make a few of the perpendicular cuts all the way to the wood at some of the particularly tight radii but these few exceptions should be easy to hide.

I've started covering it in Tweed! I used hot hide glue for this so there are some gaps in process pics but I'm going to try and give a pretty detailed explanation of how I did it. Hide glue is pretty forgiving and allowed me to soften spots with a hairdryer and fix minor mistakes along the way.

I started by drawing a centerline on the back side of the tweed along with locating marks so I could quickly flip the back and position it so the fabric pattern was where I wanted it. I covered the back with glue, flipped it into place, and kept pressure on it for several minutes. I repeated the same process for the top.

Once the glue had dried I moved to cutting out the internal features. I made cuts into the fabric perpendicular to the wood. After brushing in some glue on the edge of the plywood I pulled the excess fabric tight and taped it in place.

I repeated this on the speaker hole and control cavity. The pickup hole was a bit tight for clearance so I just cut that off without wrapping it around to the back.

With all of the internal features done I couldn't help but see how my overall hardware scheme/look was coming along.

The last loose end as far as "woodwork" was something to hold the battery in place. I modeled a receptacle in fusion 360 and 3D printed it. This one is just a test, I have a little bit of wood filament left from my 3D printed guitar that I'll use for the real deal. It includes a wiring channel so I can hide some of the wiring that needs to run between the top and bottom sections. The placement of the battery is such that you can see the built in charge indicator.

I finally have enough stuff figured out to start moving towards permanent assembly. I super glued dowel pins into the top and back plates for locating. I then used wood filler putty to fill all the in process holes along with a few other minor defects. With everything filled and in place I gave it a final sand with 180 grit. I tend to like the look of blocky Teles vs deep round overs so I just broke the edges with sandpaper. The tweed cloth makes a bit of a radius when bent over a sharp corner so between that and the slight edge break it should end up about where I want it.

After some slight delays I've finally made a bit of progress! I used a hole saw to begin turning the pickguard into a "grillguard". I used the cutout piece to test a few different processes and settled on this method. First I scuffed the entire surface, when I left it shinny in the test it was easy to see unevenness in the glue. I cut an oversized piece of grill cloth and stretched it a little bit by taping it to a flat surface. I then spread a thin coat of superglue onto the scuffed pickguard and placed it face down on the stretched cloth. After the glue dried I went around the perimeter of the guard and made cuts at approximately .125" to .375" intervals. I wrapped these strips around the back, pulled them tight and secured them with additional super glue. There are a few edge spots that are a little rough but overall I'm pretty excited with how well it turned out!

I left it hacked together for way too long because of how fun it was to play but I finally got the nerve to tear it apart and get back to work. I pulled the electronics out and took detailed notes on the wiring, still haven't turned it into a schematic but I'll get around to it sooner or later.

I also mixed up some shellac to test finishing options. This is my first time working with tweed, and shellac for that matter, so I wanted to try a few configurations to see what looked best. Board 1 has straight shellac, board 2 has a little amber dye mixed in. On both boards the left tweed sample was coating side up and the right was fabric side up. The fabric side up samples really soaked up the shellac and still have a little more of a fabric feel than I'd like. I think the final product is going to be coating side out with a touch more amber dye than the test sample.

I've got a trip planned this weekend to finish up a few woodworking loose ends and then I'm going to start assembling it for real!

The first demo is though my Line 6 Flextone III, no crazy settings or effects. It's hard to see the controls in the video so here is what I did. I start on the clean Channel, tone 10. Leaving the tone at 10 switch the the rhythm then finally lead channel. I roll the tone back to O and then work up through the rhythm and clean channels. With the tone still at O I head back through the channels with a little bit of soloing. All of the passive components are switched by leg one of the selector switch

Clean: .02uf  Tone Cap

Rhythm .047uf  Tone Cap

Lead: Cocked Wah Cap/Resistor Pair (did a lot of guess and check here, will have to get component values/wiring later)

Its not perfect but I added a little orange tape to the controls to make them easier to see. This video is the onboard amp and starts on the clean channel with the tone at 10. It's kind of just playing around with the different settings but should give you an idea of what the controls do. The passive components are obviously still switched the same but the second leg of the switch is as follows:

Clean: Nothing!

Rhythm: Adds Clipping diodes after V1b

Lead: Adds A bypass cap to V1b

I'll probably mess around a little more before finalizing it but I'm pretty happy with the tonal options this set up gives. When I tear it apart to clean up my wiring I'll get a schematic put together as I'm sure my explanation was hard to follow.

A benefit of working with low voltage tubes is obviously safety. With no possibility of deadly high voltage floating around it made it a lot easier to tweak the circuit on the fly. I drilled the hole for the output jack and wired it up as shown in the schematic. I don't have a stereo cable so I haven't tested the return feature yet but its seems to function as intended; the onboard amp runs with no cable and I can still get a passive signal out when plugged in. Switching back and forth between those options I started swapping around components and signal paths to try and dial in my 3 "channels". I honestly lost track of the actual wiring and will have to reverse engineer it to get a schematic but for now I'll try and talk everyone through the controls.

The tone pot pretty much just bleeds signal to ground, I have a few different caps hooked to it through the selector switch.

I removed the volume pot. In previous tests I got a more useful control with the guitar volume, I didn't have the right value pot laying around to replace it so for now its omitted.

The pickup selector switch sets the "channel". I'm shooting for a clean, rhythm, and lead channel. With some minor differences this should work for both the internal and any external amp. I've got a few videos to post, I'll add more explanation there.

3 hours ago, curtisa said:

However if you can run the whole thing on a 12V battery pack you can do away with the dropping resistors altogether

That would be ideal, I'm only searching for other options because of sunk cost in the 18V battery I have. When I originally sourced it I was thinking more about packaging than electronics, all of the 12V drill batteries I found had stop tabs that increased the thickness past what I was looking for. In hindsight that wouldn't have been a big deal and would have simplified everything else but... here we are. If there's ever a next one it will be 12V for sure!

19 hours ago, curtisa said:

Maybe consider rearranging the cathode resistor switch on the bottom of the 12U7 such that one resistor is always present to ground

Solid idea, I'm not sure exactly how the switch operates but it still couldn't hurt to set it up this way. 

19 hours ago, curtisa said:

Any scope for reducing the battery voltage down to 12V

https://frank.pocnet.net/sheets/127/1/12U7.pdf

http://www.r-type.org/pdfs/12k5.pdf

The tube data sheets list the heater voltage range from 10 - 15.9V with a drop in life expectancy operating on the high side.

This schematic was mostly to figure out signal flow but it should give a little insight into the amp workings. The values below are what I used in for the demo; minus the tone pot, "effect loop", and selector switch. I also had no negative feedback. I used a combination of borrowing from other schematics and what I had laying around so they probably aren't final values. Figured it was worth chasing out packaging and signal flow issues before I got too hung up on designing for tone.

C1: .022 µF (Tone)
C2: .1 µF
C3: .022 µF
C4: .015 µF
C5: 2.2 µF (electrolytic)
C6: .1 µF

R1: 1M
R2: 47k
R3: 27k
R4: 220k
R5: 220k
R6: x
R7: x
R8: 3.9k
R9: 1M
R10: 22
R11: x
R12: x
R13: x
R14: x

Tone Pot: 250k
Volume Pot: 1M
V1: 12U7 (Pre Amp)
v2: 12k5 (Power Amp)

I basically cut all of the parts off my first amp mock up and soldered them back on to a new board that fit in the depth of the body. Its a huge mess still but it worked, the amp is all on board now. I'm using two batteries because I still don't have a way to step down 18V to 12V for the heaters.

I didn't include cathode bypass caps when I put it back together and lost a ton of volume. I haven't checked everything yet to see if I missed something else or have a bad connection but it also cleaned up a lot. I have one lug of the selector switch in mind for switching V1B's cathode resistor/capacitor pair and with this new data point think that will control how much distortion it has pretty well. The other leg I was thinking about using to vary negative feedback but it could also switch another cathode if need be.

Anybody see any glaring issues with my schematic? Any suggestions? At the bottom left of the schematic I have a possible heater set up, can I just use resistors to drop my voltage as shown?
 

As a quick update on progress I pulled the back off and made a 1/4" plywood spacer so I could reattach the neck. With the back now open I mounted the transformer. It was my last heavy component with location options so I mounted it low and as close to the back as practical as the guitar is a little neck heavy.