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

iTunes Nirvana…

So, I recently added a NAS to the network. I also added a new Mac mini. My goal was to have all the media stored on the NAS and shared it out to all the computers on the network. Since iTunes allows you to share your library, and the ReadyNAS has an iTunes server built-in, I thought this would be a piece of cake.

However, there were a few hiccups that delayed my achieving iTunes Nirvana:

  • You can’t create playlists from iTunes shared libraries
  • FrontRow doesn’t show artwork for items on shared libraries
  • You can’t sync your iPod to a shared library

Clearly, these limitations make the shared library approach less than ideal.

“Ok”, I thought. “I’ll simply point iTunes to the shared volume where the music and the library file reside.”

This didn’t seem to work. No music appeared in the iTunes browser window. After trying several permutations of this arrangement, I gave up.

My last thought was to make a soft link, or “alias” in Mac parlance, to the shared folder and name the alias “iTunes”. I deleted the “iTunes” folder in my home directory, “~/Music/iTunes”, and created the alias there.

The alias points to a mounted shared volume from the NAS

To my surprise, this worked (I really didn’t think it would). The only painful part is that you may have to rebuild your library, losing ratings, etc. However, all the limitations of the shared library are now gone.

I did encounter some issues where iTunes reported a corrupt library file, but I think it was due to my stopping the “importing library” process when I first started iTunes after making the library change (it was late and the import was taking a really, really long time). I also had to “consolidate library” to get some of the content that was local to one of the computers. Another issue I encountered was that startup of iTunes was slow. No biggie. I think the benefit of the remote library outweighs the performance issue. Speaking of performance, the final issue I uncovered was that FrontRow seemed to experience weirdness if iTunes is open. It claimed that there was no content in the library. I quit iTunes, and FrontRow was happy. This may have been due to the delay incurred by the network communication, but it seemed to be related to iTunes being open.
<EOL>

UPDATE: I continued experiencing the weirdness where iTunes on the mini would report a corrupted Library file, and recreate the Library from the Library.XML file (very time-consuming). I suspected this was due to something that the iTunes Helper application was doing. To test this hypothesis, I disabled the helper by selecting (in iTunes) Preferences->Syncing->”Disable automatic syncing for all iPhones and iPods”.

Disable auto-syncing to prevent file sharing violations resulting in Library rebuilds

I think it should be OK to have this enabled on one machine, but I haven’t tested that out. For me, manually syncing my iPod isn’t a big deal.

Also note that you should select “Copy files to iTunes Music folder when adding to library”. Sine your Music folder is on the network now, you’ll want all your content going there.

Be sure to keep all your files in the same place

<EOL>

there comes a time in everyone’s life…

when they realize they’re really getting old. The other day, I saw a Wendy’s commercial. The song being used was “Blister in the Sun” by the Violent Femmes. Back in my day, that song was an anthem for the misfits, freaks and nerds. VF was the band that embodied the struggle of the outcast in a society of jocks and cheerleaders.

And now, it’s the background track for a Wendy’s commercial. Lovely. Although I’m sure that’s how the previous generation felt when their music was used for the shameless foisting of schlocky upon the unwashed masses.

Guitar Guru

Haha! Via Music Thing, this is the funniest Flash animation I’ve seen since I first watched Homestar Runner. Mr. Fastfinger is a guru that can play M34n Lix0rz. It’s interactive, so you get to make him jam and you have to use his abilities to defeat a demon accordionist. Very funny!

<EOL>

I hate iTunes music store…

because they’re going to end up with all of my money. Okay, to date, I’ve spent only about $30USD, but the fact that I’ve spent any money at all is a testament to the draw of iTMS.

For the most part, music I’m looking for is there. There are a few big examples of absent artists (the Beatles for instance), but it changes every day. Also, you gotta love the fact that you can audition a track before you buy it. And, at $0.99 per track, it’s sooo within the impulse buy range.

At first, I thought that this type of buying would severly limit my musical breadth, but there are a few things that mitigate the narrowness. First of all, the search feature tends to be “greedy” in its matching. That is, things that aren’t exactly what you were looking for appear, and I tend to investigate those results further. For the most part, I’m not interested, but every once in a while, I find something I normally wouldn’t have sought out and like. Also, these other results tend to remind me of other things I was looking for. I’m one of those people who knows exactly what music he’s looking for… until I step foot in the music store. Then my mind draws a blank. This happens in the video store as well and results in a complete sweep of the recent releases.

But I digress. The other factor that mitigates tunnel vision when purchasing music is the fact that you can audition all the tracks on an album. I used to go by the maxim of, “if there are 2 good tracks from one album, consider buying it”. I no longer need to worry about this any more. I can audition all the tracks, and if I only like one, I buy it.

So, if you haven’t yet discovered iTunes, by no means should you click this link and download iTunes. And by no means should you enter your credit card info. You have been warned.

<END OF LINE>

fixin’ maniac…

It all started with that old ADA preamp. Since then, I’ve fixed Ken’s Tobias bass (just needed to re-solder a wire to a potentiometer), and I’ve revived my old fretless bass.

Way back in 1992, I bought my first bass. I don’t even remeber what brand it was, but it had a cherry burst finish, and a small body. I really liked that bass. I had it setup by the one guy in my hometown who *really* knew how to set up a guitar. Dave Pickett was his name, and if Pickett couldn’t fix it, it couldn’t be fixed. Needless to say, when I got it back, it played like a dream.

Then a friend of mine, Jay, wanted to know if I’d trade him for his fretless. He needed a fretted bass to do some recording. He sweetened the deal by throwing in a Crybaby wah-wah pedal. This was an offer I couldn’t refuse. So, I traded my first bass for this fretless and the wah pedal.

Many years passed, and since I didn’t play enough to be good at the fretless, I really didn’t play it much at all. Eventually, I moved out to the east coast and got the itch to play again. Unfortunately, years of neglect had taken its toll on the fretless. The battery for the active electronics had corroded and took the battery connector with it. Also, the output jack corroded. I thought it was finished. “Maybe one day I could fix it”, I thought. And so, it lingered amongst my possessions until a few days ago.

With my new-found interest in fixing things, I thought I’d fix my gaze upon this old thing and give it a shot. I looked at the electronics, and it looked like I really just needed to replace the jack and the battery connector. Everything else seemed to be okay. So, this Saturday, I headed over to a local guitar shop and got the jack and the connector. A grand total of $12. I figured it was worth that much to see if it was fixable. If it didn’t work, I was out $12 and I could get rid of the bass with the knowledge that I had at least tried to fix it.

To make a long story short, after one failed attempt, I realized my mistake and rewired one of the connections. That did it! I plugged it in and I was in business. How cool is that?!

<END OF LINE>

ADA MB-1 tube bass preamp

About 5 years ago or so, I purchased a bass preamp from my bass instructor/mentor/friend, Rusty Springfield. The ADA MB-1 was a real masterpiece of engineering, and had both a tube portion as well as a solid state portion that could be mixed together for that “perfect sound”. This unit had seen a lot of use, as Rusty used it in his travels with the Big Apple Circus, and it survived roadies, tent dust, and endless use. So, when I decided I wanted to do a little home recording, he was willing to sell it to me for a good price.

All was well until about a year and a half ago. For some reason, the little guy would just stop working and dump its programming. If I could get it to work, bumping it would upset it again. I searched for a place to repair it, and after much procrastination, took it in. The guy said it would cost around $60 bucks just to bench it, and then he still didn’t know if it could be fixed. And, since ADA had been out of business for some time, he didn’t know if it’d be worth looking at.

So, I went online. There were places that could repair and service it, but it was still going to be pretty expensive. So, for the time, I gave up, and chalked it up to “well, I got good use out of it while I had it”.

Fast forward to last week. As you know, I’ve started a new job, and in the course of 5 months, I’ve learned a lot about hardware, and much has been demystified. So, armed with these new learnings, I decided I had nothing to lose by at least taking a look at the preamp and see if it could be fixed. Worst case, I’d need to replace some parts. The guys at work could probably figure out what I didn’t know, so the prospect was good in my mind. So, I opened up the case and looked around. Lots of chips and lots of other electronics that I have no clue about. So, I decide that maybe a chip is loose. I start poking around with my fingers on all the chips that are mounted on sockets. There was a lot of creaking and flexing of the mainboard, until finally, one of the chips I pushed on gave a little. Hmmm, it seems it was loose after all. So, I plugged it in, and, “voila!”, the preamp ran through its normal POST, then warmed up the tubes, and displayed its normal screen. Needless to say, I was ecstatic. I immediately plugged in my bass, and there was nothing but sweet, sweet music 🙂

WooHoo!

END OF LINE