Whisper Amp Strap Clip

Back in 2015, there was a kickstarter for an all-analogue, tough-as-nails practice amp for guitar and bass. Intrigued, I followed the project. The project was successfully funded and I ordered my unit once the web site went live. It is a great little gadget! I ordered the kit, as it didn’t have that many parts and I needed to improve my soldering skills. I spent an evening assembling it and have used it mostly at night when the kids are sleeping. Another great use is taking it along with me to guitar shops so I can compare other guitars with the same amp.

My only complaint with the Whisper Amp was that I had to find a place to put it. Putting it in my pocket was a little awkward with the guitar cable protruding from the top. So I got to thinking about a way to attach it to my guitar strap. I wanted it to be relatively easy to attach and remove, so I knew Velcro would be involved somehow. As I often do, I turned to OpenSCAD to put my thoughts together. My first attempt was a solid band with a loop for a nylon strap. I would use 2 of these and fasten nylon through the loops. The problem with this design was that there wasn’t a good way to keep the bands secured to the body of the amp.

Initial design

I quickly devised a second design and sewed together some straps with Velcro fasteners. This worked a little better, but it had the same problem. I needed a different approach.

The second prototype was easy to attach and remove. A little too easy to remove, though.

The final design solved the attachment problem by securing a nylon strap between 2 “caps” on either end of the amp. This proved to be much more secure, but required a lot more design time to get the proper shape of the caps and the placement of the cutouts for the connectors. To get the curves on the edges of the caps, I resorted to tracing the shape of the amp on paper and calculating the radius of the rounded edge. Primitive, but it worked! To achieve this effect I used the minkowski sum function in OpenSCAD. It’s a really useful tool for nicely rounded edges. for the strap loops, I planned to use 1″ nylon webbing, so I made the loops accommodate one layer.

The bottom cap
The top cap with cutouts for the headphone and 1/4″ plugs
FIRST TRY!!!

In a rare flash of maker inspiration, I got the measurements correct the first time. Well, on the rounded corners, anyway. I think I had to reprint due to the plug cutouts being a few mm off. I wasn’t sure how to finish the edges of the nylon. A quick search seemed to indicate that heating the frayed edges would melt them and nicely seal them off. I waved the cut ends over a gas flame on the stove, being careful not to hold it there very long. My caution paid off, as the ends melted quickly, finishing up very nicely. I sewed in a few pieces of Velcro and got it all assembled

Ready for action

Interesting note about using a 4-segement plug (TRRS). The output jack is designed for 3-segment (TRS) plugs, so you may need to slightly adjust the position of a TRRS plug to get stereo output.

And, finally, here’s a photo of the amp attached to a guitar strap while playing

I attach the amp near the end pin of the guitar

Overall, I met my objective of making an easy-to-attach clip for the amp, which means it’ll be falling off of tables and other places a lot less. If you’re interested in making one, or just want to see how I designed it, I’ve put the STL files on thingiverse!

I Like Big Buttons

The Premise

In early 2018, my friend Steve had an idea.  His church supports missionaries, and for fundraisers, they sell lunches to the congregation.  In the past, they had volunteers prepare and serve the food.  It was a lot of effort, and Steve thought that it could be improved.  He thought that having a restaurant make the food would allow them to charge a bit more for the food, and might draw more attention.  He was right of course, and now he wanted a way to engage the participants even more.  He wanted some kind of visual progress indicator.  something that would get people excited about participating in supporting the cause.

“What if we had a big button that people could push when they buy a lunch, and then have a big display of how many lunches we’ve sold?”

That sounded like a cool idea to me.  So, I set out to build just that.

The Architecture

button box setup
If this is a smart TV with a browser, the laptop can be eliminated

I tried to make this as simple as possible. No, really I did!  However, the constraints of the environment dictated otherwise.  I thought the simplest thing would be to have a button attached to a Raspberry Pi, which would be attached to a screen via an HDMI cable.  However, the display needed to be relatively far away from where people would be paying for lunch, and running a long HDMI cable was not acceptable.  Steve mentioned that they had an extra laptop that they could connect to the TV, so this seemed like a reasonable solution.

After some noodling, I decided that I’d have a big button box with a Raspberry Pi inside. The Pi would host a web server that publishes a page with the count on it.  The laptop connected to the TV would access the web page and display it on the TV.

Is this the simplest design?  Not by a long shot.  Would it be fun to build?  Absolutely!  I also like the idea that this solution is self-contained.  If the TV has a browser, then the laptop can be removed from the setup.

The Button Box Design

large button
That is one big button!
lit button
Ooh! Shiny!

The hardest and most interesting part of this project to me was the button box.  I’d been itching for a project to use the laser cutter at our makerspace, theLab.ms.  While I could have just used a tool to generate the dimensions of the box with appropriate notches for assembly, I decided it would be fun to figure it out on my own.  Here’s what I wound up with…

2D OpenSCAD layout
the 2D primitives in OpenSCAD were perfect for this project!

I made the first prototype with cardboard, which worked out perfectly!

Cardboard prototype
looks good so far!
cardboard prototype assembled
Everything fits with a reasonable amount of space for wiring

Happy with the results, I moved on to the 2nd prototype, which was made out of MDF scraps at the makerspace (I think I also got some hardboard in there, too).

MDF prototype bottom
All the holes lined up! The square plate on the lower left is the shutdown button.
detail on shutdown button
I mounted a momentary contact button upside down to serve as the shutdown button

Since this button box would be operated by non-technical folks, I decided I should add a shutdown feature to prevent damage to the SD card.  When the button is held for 2 seconds, a shutdown command is sent to the Pi.  Of course, nothing stops the user from just disconnecting power, but at least the capability is there.  Since the Pi doesn’t have any built-in capability to shutdown the OS, I added a momentary contact button to the bottom of the box to serve this purpose.

Everything was going great until I received my acrylic sheets.  I thought I was getting 3mm acrylic sheets, but I actually ordered 2mm acrylic sheets.  *sigh*.  But thankfully, I made the material thickness a variable in my OpenSCAD model, so I just needed to change that variable from a 3 to a 2, and adjust the placement of the power connector hole (that took a bunch of trial and error).

off my 1mm
PSA: 3mm does not equal 2mm

After the adjustments, I re-cut the box from the spare sheet of acrylic (always a good idea to get more than you absolutely need in case you make a mistake!).

final internal wiring
I really like the Perma-Proto hats from Adafruit!

To keep the wiring nice and clean, I used a Perma-Proto hat from Adafruit. I’ve used them in a few projects now and I’m hooked.  For the relatively small circuits I’m making, they’re perfect, and don’t add much to the footprint of the project.

finished box unlit
I like the way it turned out! Unfortunately, you can see along the top front edge where the acrylic cement leaked and marred the surface. A little acrylic cement goes a long way.
finished button box powered on and lit up
Who can resist a giant shiny button?

The RESTful Web App

I really enjoy projects that involve physical builds as well as software.  In the spirit of over-engineering things, I decided to make my counter a RESTful Web Service.  You can find the source code on bitbucket.  When the big button is pressed, python code sends an HTTP request to the web server, incrementing the stored count.  The web page showing the count updates every 1/2 second.  For the shutdown, holding the button on the bottom of the box sends another request that executes a graceful shutdown of the web server and the Raspberry Pi.

A Demonstration

Here is the whole thing in action!

Next Steps

  • Test it out in the target environment
  • I’d like to make the typeface fixed-width
  • There is code to set a target number.  I’d like to add some animation that is triggered when the goal is reached

You Can’t Scare Me!

Over winter break 2017, my older daughter asked if she could make something. Before I even knew what it was, I was pretty excited. Finally after all these years of trying to show my kids that they can make things, I see a spark of interest. Here’s her idea in her own words:

“I want to build something that people can attach to their glasses so they can see who or what is behind them.”

So, we set to work on the design. I had her draw up her initial thinking on paper, and we took it from there. She decided that for the prototype, a clip would be the easiest way to attach the unit to her glasses

I wasn’t sure what we could use for the actual mirror part, but I remembered seeing mirrored acrylic somewhere, so we searched for mirrored acrylic sheets. We ordered the parts and set to work on designing the bracket that would hold everything together.

We decided that 3D printing the bracket would be the most efficient way to prototype it, and that turned out to be true.

Her first idea was a ball joint because it would allow the wearer to adjust the mirror’s position precisely. So, we found a ball joint on thingiverse and scaled it to the size we needed. The print didn’t work at all, and the joint wouldn’t fit together. Getting this joint to work for us would require a lot more engineering.

Discouraged but not hopeless, I decided I’d show her how to use OpenSCAD to design our own part. I mean, how hard could it be? We’d just create a static bracket for our first try and see what needed to be adjusted.

Using OpenSCAD was a great way to incorporate some of the math she’d been learning in school that year. We had to measure the dimensions of the clip with the vernier caliper and then calculate dimensions of the bracket based on those dimensions. She seemed to really enjoy the challenge.

Second design
The very first design connected the mirror mount at the edge of the mirror. After testing, she found this was too close to the eye and decided to move the mirror away from the eye a bit, resulting in this layout.

The next step was to put all the pieces together for the first prototype.

We had some hot glue available to us, and that worked… for a few hours. The failure of the hot glue would later clue us in to a design flaw.

Despite that, the first prototype achieved its goal. She decided that the mirror was too close to the glasses, so we should move the mirror outward a bit. We fired up OpenSCAD and adjusted the dimensions and printed again.

First Prototype
The First prototype had the mirror closer to the eye, which turned out to limit the visibility too much.

This time, we used Loctite silicone to bond the clip to the bracket. That joint lasted a bit longer, but still failed after about a day. As a remedy, we decided to use Gorilla super glue.

After gluing the parts together, one part of the joint failed again.

I decided I wanted to figure out why the glue joints were failing. I inspected the action of the clip and showed it to my daughter. We hadn’t taken into account that the clip’s spring expands past the clip’s edge when the clip is actuated. The slight expansion was causing the glue joint to flex and eventually break.

She also noticed that she couldn’t see that much around her and we discussed concave and convex mirrors.  So, we iterated on the design and came up with a curved mirror mount.

Curved Mirror Mount
This mount allows the wearer to see more of what’s around them.

By this time, we were running out of time, so we weren’t able to make more prototypes before school started back up.  We had a lot of fun doing this, though!

Issues for Further Development:
– how to make the fastener more generic to fit more types of glasses?
– carve out a small slot to accommodate the spring expansion.

The Rickrolling Toilet

The Idea

In 2015, my church decided to revive their Fun Fair event.  They encouraged folks to take a look at some of the old games and refurbish them if they were interested.  I found an old game called “Dunk It”.  It consisted of a toilet seat bolted to a green wooden frame.  The goal was to toss a roll of toilet paper through the hole of the toilet seat to win a prize.

My inner 5yo. thought this would be my game.  But, I couldn’t just leave it as is.  I needed to make some… improvements.  The premise of the game was simple, but it lacked something.  There was no feedback for the player.  So, I set out to give it a voice.

My first inclination was to use an Arduino with an audio shield.  However, I was trying to minimize the cost, so I thought I’d use something I  already had on hand, a Rapsberry Pi A+.  This would handle the audio, and the programming would be relatively simple.

Alpha/Beta Version

To prove the concept, I thought I would wire up a light sensor (Light-dependent Resistor) to the Raspberry Pi.  This was not as straightforward as I’d hoped, since LDRs are analog devices and the RPi only has digital I/O pins.  So, after a bit of searching, I found a technique to read analog values from a digital I/O pin using a simple circuit.

Once I got this wired up, I stole some code to make the LDR reading work.  I combined that with some code to play back audio and the alpha version was working…

Version 1.0

I foolishly ignored the advice to always put a resistor in series with an LED.  And it bit me in the behind.  An hour before the fun fair, the LED blew out, and I wasn’t able to leave and get a replacement.  Lesson learned.

Version 2.0

For Version 2.0, I wanted to make some significant improvements.  First, I wanted to make a more realistic “experience” for the players.  I was able to secure a toilet on freecycle (I love freecycle).  After sanitizing it, I set to work wiring up the LED in the bottom of the bowl.  This had the added benefit of making the code simpler.

I also wanted to improve the sound for the game, so I got an inexpensive power amp and car speakers.  I mounted the speakers on the snazzy new platform with locking casters.  This made the whole thing much easier to move around.

Version 3.0

For version 3.0, I wanted to clean things up significantly, and make it easier to assemble/disassemble.  I mounted the amp and Raspberry Pi on a board, that attaches to the inside of the tank with Velcro.  I also used a connector for the sensor instead of being wired to the board.

all components mounted to a single board
I wired up the circuit on a proto hat and added a connector for the LDR so that it was easier to connect/disconnect

Debug mode with monitor and keyboard
What toilet wouldn’t benefit from a debug monitor and keyboard?

Version 3.1

I added a shutdown button for the system so the SD card doesn’t get trashed, and the Pi shuts down gracefully. and covered the wires with some flexible split tubing.  I also added some code to avoid repeating the audio if the sensor detected darkness at the end of the previous audio playback.  Finally, I added some other… apropos sounds.

I bet this is the first time the words “graceful” and “toilet” appear in the same context.

Shutdown button on the Pi Hat
I added a shutdown button. This puts my mind at ease by gracefully shutting down the Pi.

Possible Improvements:

  • I’d like to use the flush handle to perform the shutdown/recalibration

Resources

About a Guitar

In the Beginning

When I was a kid I got an Aria Pro II XR Series Electric guitar as a gift from my parents.  The mists of time prevent me from recalling if it was for my birthday or Christmas or some combination of the two, but I’m fairly certain that it was 1989. 

Identity masked to protect the guilty. It was the '80s!
Christmas or Birthday? Please excuse the mullet.  Identity masked to protect the guilty.

I played the heck out of that guitar for many years, and it has moved with me everywhere I’ve gone.  After our first daughter was born, I didn’t play very much at all and it languished until recently.  I got back into playing a few years ago, and longed for a new guitar.   I finally got that new guitar and passed on the Aria Pro to my older daughter.  She liked it, but said that she’d like to have a blue guitar.  That was exactly what I wanted to hear!  I’d been contemplating modding a guitar for ages, and this was the perfect excuse to try it out.  We decided to refinish it, upgrade some of the hardware, and maybe even audition some different pickups.  Before tearing it apart, I thought I’d take some commemorative photos!

Headstock
I’ve always liked the headstock on this guitar. Perhaps not the best mechanical design, but it looks cool!
No Pickguard
The lack of a pickguard adds to the minimal aesthetic of this guitar.  One of the things I dislike about low quality tremolo systems is that they are a pain to tune and keep in tune.  After finally paying for a decent setup several years ago, this tremolo was tamed for the most part.
Treble side cutaway
Not the best design for easy access to the upper frets, but I never play up there anyway.
clean and simple
I’ve always appreciated the clean lines and simple arrangement of this guitar. Also, it’s black.

Step 1: Disassembly

To refinish the body, we needed to remove all the electronics, plastic covers, hardware and the neck.  This was the easy part!

Korean pots!
Korean electronic components!
Removing Knobs
These knobs had no set screw. I found this tip online. Use a pair of spoons to gently lever the knob from both sides. Worked like a charm!
Pickup wiring
The wiring for the pickups is nice and tidy. Almost a shame to remove them
bare body front
all components removed
bare body back
An empty husk

Step 2: Remove the finish

After reading a few different posts about refinishing late ’80s Korean guitars, I decided it’s probably safe to try the heatgun + paint scraper technique.  I had no idea what to expect, but read several posts indicating that this vintage of low-cost guitars would likely have a laminate body.  I was hoping that there would at least be some semblance of an interesting grain to the revealed surface.   There’s only one way to find out, I suppose!

Heatgun and paintscraper at the ready
I normally don’t like either of these types of tools anywhere near my guitar

As it turns out, there was a thick coat of finish on top of the wood, then a layer of paint, and then a protective layer over the paint.  Removing all of this revealed a somewhat porous laminate beneath.  The layers of the laminate are about 1/16″ thick each, and actually revealed a very interesting pattern at the contours of the body.  The top layer itself wasn’t particularly interesting, but that’s okay, since the laser-etched images should give it some visual interest.

partial finish removal
I guess it takes a LOT of finish to smooth out the laminate bodies. That stuff is thick!
some scorch marks
Unfortunately, I let the heat gun linger too long in a few places and ended up with several scorch marks. I was able to remove most of it with some careful sanding, but not completely.

Once the finish was completely removed, I set to work with the random orbital sander to get a nice smooth finish.  I ended up with 300grit or so, and that gave a nice, almost glassy smooth sheen to the wood. I was able to remove much of the scorch marks caused by incautious use of the heatgun.

showing the laminate structure on the back contour
I think the way the countours expose the laminate layers is really interesting!

Step 3: Frickin’ Lasers

Not content with a plain design, I asked my daughter if she wanted to put any custom designs on the guitar.  Of course she did!  So she set about drawing a few things she wanted on the guitar.  She said sloths and cats had to be involved.  In our search for ideas, we came upon an adorable image of a sloth hugging a cat, and she had to have it.  She then drew her own sloth and a cat from her favorite book series at the time, Warriors.

positioning laser cut designs
we played around with the size and layout of the custom designs.

After drawing them up, we scanned the images and tested them on some scrap material to make sure we liked the results

sloth hugging cat on MDF
Aw, so cute!
sloth hugging cat on guitar body
Since the wood is denser than the MDF, the detail isn’t as pronounced, but it’s still cute!
Jayfeather design on the guitar body
I believe this is “Jayfeather”
Sloth design on the guitar body
That’s one hungry sloth.
both designs on guitar body
We were happy with the placement. Luckily, it didn’t require high precision for the placement.

Step 4: The Headstock

I wanted to really personalize the guitar, so I decided we should “rebrand” it.  First, I sanded off enough of the finish to remove the paint and the logo.

sanded headstock
It didn’t take long to sand down just enough to get rid of the old decal and the paint layer

I then took the Epiphone logo and played around with it in the Gimp and came up with this:

"Eden" logo and chop
“Eden” logo and chop

And applied it via a waterslide decal

waterslide decal of logo
Working with the waterslide decal reminded me of the decals that came with airplane models from the ’80s!

Step 5: Re-finish

One of the goals of this project was to have a nice finish that was easy to apply and didn’t require a lot of equipment.  I opted for tung oil, as I like the look and feel of the oil finish, and it can be applied by hand with good results.  As for the new color, we originally chose a deeper blue, but found that it was too dark and didn’t seem to want to stick to the wood.  We removed most of that darker blue, leaving traces of it behind for visual interest and tried a much lighter, transparent antique blue.  This was a much more pleasing result.

dark blue stained body
This stain was too dark, and didn’t show much of the wood.

lighter stained body
This stain was less heavy-handed and what little character the wood has is visible. We left some remnants of the darker stain to give it some variation in appearance.

After settling the stain issue, it was time to apply the tung oil.  I think we applied 9 coats of tung oil.  It really started to get a nice soft shine after about 4-5 coats.

body front with tung oil finish body back with tung oil finish

Step 6: Re-Assembly and Upgrades!

So, this was the hard part.  Getting all that stuff put in place and working properly is always a challenge for me.  I tend to get myself into trouble by not documenting things as I take them apart.  I was careful to avoid that mistake this time.

neck bolts being inserted
I screwed in the neck bolts until they just poked out of the body. Then I attached the neck and completed the assembly.
guitar back assembled
so cute! The black hardware actually looks decent with the lighter blue finish.
finished guitar front
And, it’s done!

I’m not the best with a soldering iron (working on it, though), but it appears that I got all the connections together correctly.  The guitar makes sound and it sounds like a guitar.  I consider that a win.

I took this opportunity to do a few upgrades.  I wanted to improve a few things.  Firstly, this guitar broke a lot of strings.  Like a ridiculous amount.  Long ago, I suspected that the poor quality nut and bridge saddles contributed to the problem.  During disassembly, I happened to break the nut, so I needed to replace it anyway.  So, I ordered a Graph Tech Tusq nut and a set of their String Saver saddles.

closeup of old bridge saddles
The old saddles had a sharper break angle, and the set screws scratched my hands.
Closeup of new bridge saddles
The Graphtec saddles have a smoother break with a rounded channel and the set screws are flush or nearly so. Much more comfortable, and we have not broken any strings since.

I also noticed that the tremolo springs ring while playing, so I replaced them with some noiseless springs that are wrapped in plastic of some kind.  Lastly, I wanted to install locking tuners, but they are rather expensive.  After some digging, I stumbled upon these Wilkinson locking tuners.  They’re pretty ingenious, effective, and best of all, inexpensive.

How’s It Sound?

Unsurprisingly, it sounds pretty much the same as before.  We didn’t end up changing the pickups yet.  But for the curious, here’s what a late ’80s Korean low-cost guitar sounds like

What’s Next?

Well, we have a few pickups lying around that we might try out, but honestly, there’s not a lot more we want to change.  The one thing I’d love to do is remove the tremolo system and replace it with a fixed bridge.  But, due to the nature of the tremolo design, there isn’t a good way to make the conversion.

DIY Leslie Cabinet for a Guitar Amp

The Find

the original organ
The N-222 sitting in my garage (as it did for several months)

A very nice retired couple was giving away a Hammond N-222 on Freecycle (I love Freecycle!).  So, I asked my friend, Sam, to help me bring it home.  We barely managed to wedge it into a Prius V, but eventually got it back to my garage.

After a bit of research, I learned that this model has a built-in Leslie speaker.  The organ wasn’t worth much, plus a few of the keys were non-functional.  I also learned that over the years, guitarists have used Leslie cabinets to add a tremolo effect to their rig.  I thought building a speaker cabinet out of the parts I could salvage from this organ sounded like a fun project.

What I wanted to achieve that differed from similar projects was to retain some of the original character and visual design elements of the organ.

The Disassembly

It has taken all my will power to avoid the organ harvesting puns while writing this. As I was taking the organ apart, I got a better idea of which materials from the organ I could use to build the speaker cabinet, including some buttons, knobs and the Hammond nameplate.  I was a bit disappointed to discover that much of the organ’s cabinet was made of particleboard.  The parts that were either plywood or solid wood were not substantial enough to be used in building the speaker cabinet.  At this point it looked like I would need to construct a new box from other materials.

The black square on the right is the Leslie assembly

With the guts removed

The guts

the Leslie rotating speaker assembly removed from the organ.

I also discovered a spring reverb unit in the bottom of the cabinet.  I had planned to incorporate this into the design, but I decided to keep things simple for this build.  So, I’ll do something with the reverb tank in another project.

What appears to be a type 4 reverb tank

The Design

Once disassembled,  I put some of the materials together to get a sense of the aesthetic.  I think these elements together really preserve the look of the organ.

This is what I’m shooting for visually

I wasn’t sure how to orient the parts in the cabinet, but here’s a first take at what I thought the resulting box might look like.  If you can’t see the lighter strokes, I’d intended to have the flat sides of the spinning cylinder face the front and rear of the cabinet.

a quick drawing of what I hoped the end product would look like

After some careful measuring and some reflection on how the sound will get out of the box, I changed the orientation of the sound wheel, and therefore the entire enclosure.   In my research, I found varying opinions on geometry, construction techniques and preferred materials.  I settled on 3/4″ plywood for the structure of the box, as it would result in a really strong box.  One of my favorite design tools of late is OpenSCAD.  I’ve been using it to visualize a lot of projects, and I thought it’d be useful to get accurate dimensions for this project.   I’ve put my OpenSCAD files online if you’d like to take a peek, or use them for your own project.

OpenSCAD allowed me to experiment with different dimensions and end up with exact measurements

Lastly, the 8″ speaker that came with the organ was a rather non-descript and blah-sounding affair.  I chose to upgrade it with an actual guitar speaker.  I found an 8″ Celestion Eight Fifteen (15W) speaker on Amazon warehouse for under $30.  It had good reviews, so it seemed like it was worth a try.

The Materials

I got lucky on the plywood front.  My friend, Eddie, had lots of scrap 3/4″ plywood and was generous in letting me use that instead of buying new material.  For the covering, I wanted to get tolex that would be similar in color to the wood of the organ.  Mojotone Brown Marvel Leather seemed to be the right color, and it happened to be on sale!

Mojotone Brown Marvel Leather tolex ordered through Amazon

I opted for black hardware to match the nameplate, and picked Reliable Hardware cabinet corners.  I purchased a set of 3-screw corners for the rear of the cabinet and a set of 2-screw wrap around corners for the front.  I decided against using straps, because of the size of the cabinet.  I didn’t think adding straps would make lifting and carrying the cabinet any easier than picking it up from the bottom.

The Build

Step 1: Checking That the Motors Work

Before ordering parts, I wanted to make sure that I knew how the motor worked and what would be required to switch between speeds.  I quickly wired up the motors to make sure they worked and that I understood how to switch between them.

Original circuit layout (I’m not good at circuit diagrams). I eventually removed the separate on/off switch.

Rather than having a variable speed motor, the system has 2 motors, one for each speed setting.  This was unexpected, but led to a simple solution.  I thought I would have a separate power switch and Leslie speed control.  But my friend, Ben, helped me realize I could do everything I needed to do with a single 3-position switch.

This was my first project that used AC power, and of course, I forgot about a fuse!  That was quickly remedied by using a fused AC power connector on the rear panel.

Step 2: Designing the Leslie Control and Power to the Motors

Since I wanted to use the original control button for the Leslie, I had to figure out a way to convert the button’s angular motion into the linear motion of a switch. First, I thought of using a toggle switch underneath the button, but Ben suggested a 3-position sliding switch instead. I figured I could 3-D print the parts I needed to make this work and set to work devising a harness for the switch and original button.

To incorporate the old Hammond buttons, I selected the one marked “Leslie Slow/Fast” to control the motor selection.  I went to my local makerspace, thelab.ms, and 3D printed a housing and mechanism to actuate the 3 position switch.  The switch cover plate for the button I 3D printed using a wood-impregnated filament that could be sanded and painted to match the cabinet.  However, this proved to be too brittle at the dimensions I used, and so I opted to print in black ABS.

Missing from this photo is the small collar that goes around the black switch button that translates the rotary motion of the Leslie button to the linear travel of the switch.

This is the piece that translates the rotary motion to linear motion

The switch cover printed in wood-impregnated filament.

The print didn’t turn out well, and the result was brittle.

The black ABS print turned out much better

I increased the size of the flanges to add some strength.

The button’s legs needed to be trimmed down to properly actuate the switch.

I tested the modifications on another button and verified that it worked with the assembly.

Step 3: Building the Cabinet Box.

Eddie cut the boards down to size on a table saw for me.  then, I clamped the parts together to make sure the measurements were close enough.  Things were really starting to take shape!

Sanity fitting of the freshly cut parts for the cabinet

Test-fitting the Leslie/Power control assembly, the fused AC connector and the speaker connection jack plate.

With everything test fitted, I decided to try out the sound and see if there was a discernible difference if the back of the cabinet were open or sealed.  I preferred the sound of a sealed enclosure.  Here’s a video showing the Leslie in action in both slow and fast speeds.

Satisfied with the resultant sound, it was time to put it all together.  Eddie recommended doweling the walls of the enclosure for added strength.  First, I glued and screwed the Leslie assembly to the bottom panel of the enclosure.  Then, I doweled the side panels and glued it all up.  Once it was dry, I screwed the top panel into the top of the Leslie assembly.  To say the least, it is a solid build!

Dowels installed, and glued up

After sanding down all the corners and edges

After sanding down all the corners and edges

3/8″ roundover on all the edges

After constructing the box, I sanded the edges to even them up, then I hit the edges with a 3/8″ roundover bit in my router.  The cabinet corner specs indicated a 1/2″ inner diameter, but it looked a bit smaller to me.  The 3/8″ bit was a perfect fit.

Step 4: Covering the Cabinet in Tolex

I ordered a single yard length of the tolex, which had a 54″ width.  I underestimated a bit, so I decide that the rear panel would be covered in grill cloth instead of tolex.  I am happy with how it turned out despite the error in estimation.  The hard parts with the tolex were cutting the corners.  The How-to video from Reliable Hardware shows mitering the corners, but you have to be careful not to overshoot the corners or the cuts show.  Sadly, I missed a few of them.

I tested the DAP contact cement on a small piece, shown on the left.

The DAP product is low VOC, but still has a fairly strong smell, so it might have been a good idea to do this outside.

Step 5: Final Wiring of the Motors and Speaker

The next step was to do the final wiring of the speaker and motors.  This was my first time using heat shrink tubing.  This stuff is great!

Phase 6: The Finishing Touches

I wasn’t sure how I’d cut down the nameplate, but I had a lot of room for error.  The final piece only needed to be about 12″ long, and I had about 36″ of material to work with.  My first attempt was to use metal snips.  It cut easily, but because the nameplate is c-shaped in cross-section, the snips bent the edges.  The metal appears to be aluminum, so I decided to try a cutting wheel on the Dremel.  This produced a much better edge, but was hard to steady.  I mounted the Dremel on the press stand and elevated the nameplate to the level of the cutting wheel.  I was then able to slide the nameplate across the wheel in a smooth fashion.  After making the cut, I tried smoothing things out with a grinding bit, but it made the edge uneven.  I then tried some medium grit sandpaper, and that worked well.

Cutting down the nameplate

The original grill cloth on the baffle from the organ

The slot was cut with the kerf of a circular saw. It was wide enough to accommodate the grill cloth and the edge of the nameplate.

Nameplate installed and grill cloth mounted to the new front panel

The Finished Project

Not too shabby!

My favorite part is the screws for the nameplate. I also added some loops of ribbon to the front and back panels to aid in removing the panels.

Uncluttered

I’m happy with the look of the Leslie control

The wrap-around corners paid off. I love the look!

Overall, I’m very pleased with the look and sound of this cabinet.  I’m really impressed with the Celestion Eight Fifteen speaker.  It has a lot of low-end for such a small speaker.

Sound Samples

Some Issues

  • When the cylinder stops spinning, there isn’t a way to make sure the opening points toward the front of the cabinet.  I’ve thought through a few ideas, but most are overly complex and require a lot of effort.
  • Because I wanted to keep the cabinet as compact and as simple as possible, I didn’t design in a way to replace the speaker.  If it every blows, I’ll have to rip apart the cabinet.

Lessons Learned

  • Slow down when cutting the mitered corners of the tolex
  • Fill in any surface divots or other irregularities before applying the tolex.  There’s a good chance they’ll show through.
  • Don’t touch bare AC wire connection points when they are plugged in.

Parts List

Description
Cost of needed parts only
3/4″ Plywood for body $0.00
1/4″ switchcraft panel mount jack $3.60
recessed jack panel $4.99
AC power wiring with ground 14/3, 2′ $2.00
speed switch (6 contact 3-position switch “on-off-on”) $1.28
3 point guitar cabinet corners $6.06
2 point guitar cabinet corners (wrap around) $8.96
panel mount power connector w/ fuse $1.65
Celestion Eight 15 8 Ohm speaker $21.65
rubber feet $2.49
#8 1/2″ metal oxide wood screws $2.63
Mojotone Marvel Leather Tolex $18.23
DAP Contact Cement $18.50
total $92.03

Acknowledgements

I’d like to thank Sam for not blinking when I asked him for help picking up the organ.  Big thanks to Eddie for donating the plywood and for cutting the big pieces on his table saw, as well as for suggesting the dowels (and letting me borrow the doweling kit).  Finally, I’d like to thank Ben for helping me figure out the electrical bits.

References