For several years, I’ve returned to the desert of Black Rock City for the annual Burning Man festival. I always perform at more traditional camps and stages with an acoustic violin, but over the last couple of years I’ve wanted to do something a bit different. I dreamed of having a mobile rig for my electric violin that allowed me to wander the desert unencumbered by electricity or even a stage

My first attempt at a mobile rig

I wanted to roam around the deep playa and perform as I walk. My first attempt at a setup like this was really hacked together, with a Lyon LA5 mini-amp tied with rope to a small camel backpack. I got the Lyon amplifier off of Craigslist for $15, which appealed to me because it was cheap and was powered by a standard 9-volt battery. When I tested it before buying it, I used the DC adapter and it seemed loud enough for my purposes. But I soon discovered that the amp severely limits the volume to about 0.5 watts when running off of battery power. Even still, I brought it out to the desert last year and had a great time busking. It was even a decent level as long as I turned the distortion up to maximum. But of course, that sounded horrible.

Improving the mobile rig

This year, I vowed to return again with a much better mobile rig.

I had the following desires on my wish-list:

• The total weight needed to be less than 30 pounds so I could carry it on my backpack and still be able to play my violin comfortably
• The amp needed to put out a clean signal loud enough to be heard from 50 feet away
• Everything needed to be portable for at least 4 hours, so I could play for a decent amount of time
• I needed the option of amplifying an stereo line signal as well, so I could play to backing tracks if I wanted
• I wanted the rig to be secure, but didn’t want to do too much permanent damage to any components to build the rig
• I didn’t want to spend too much, because this rig was going to take a beating (those of you who’ve attended Burning Man will understand the abuse that the environment puts on equipment)

The amplifier

There aren’t that many battery-powered amplifiers out there which hit the right sweet spot between power, weight, and cost. But I finally found a Vox DA10 on Craigslist that seemed to fit the bill perfectly. The specs put it at:

• 16.5 pounds
• 5 watts max power on batteries
• 4 hours on 6 C batteries at max power

There’s also a nice switch to drop the power down to 1.5W, if I wanted to save juice.

The backpack

The next problem was attaching it to my back. Originally I thought I could drop it into a mesh backpack so that the sound would still project, but I wasn’t able to find a mesh backpack that was the right size for the amp. In hindsight, it’s a good thing I didn’t go this route because my final result was MUCH better.

I decided to try to find an old external-frame backpack, and try and jury-rig a harness. The Vox amp is 15-inches wide, which happens to be exactly the width of many external-frame packs. I ended up finding a really old orange REI external frame pack on Craigslist. The nice thing about the older packs is that the cloth portion can be easily removed for washing, so I wouldn’t have to destroy the pack to deconstruct it.

The build

After experimenting with different positions, I found that placing the amp near the middle of the frame would be the easiest, because it would sit snugger against the frame than at the top or bottom. The only minor bit of destruction I needed to do was to remove the thin aluminum poles normally used to provide separation between the backpack and your body. The poles were not permanently attached to the rest of the frame, and only required some force to pull out. I bent the poles in the process, but I have the feeling I could re-place them into the backpack again if need be.

I went to the hardware store to figure out ways to attach the frame to the amp, and realized that the pins that normally held the pack to the frame would work perfectly to hold the amp in place, if I found some brackets to screw into the amp body. I figured that 4″ mending braces would probably work. Attaching the amp this way gives me the option of easily removing it just by removing the wires that hold the pins in place. I could even get access to the back battery compartment by just removing two of the pins and swinging the frame up.

Luckily the screws were just BARELY short enough to prevent drilling through the wood of the amp, so I didn’t have to worry about drilling into any electronics. I drilled pilot holes into the side of the amp before screwing the braces in with screws, to prevent stripping the particle board the amp’s cabinet is constructed out of. I installed the braces at 45-degree angles due to necessity, but it also prevented the amp from wiggling around at all.

I made sure that the holes for the mending brace were large enough to accommodate the pin that would attach to the frame. It was a perfect fit!

Now that the amp was attached, I wanted to figure out a way to have the amp easily stand up when set on the ground.

I took the internal frame spreader from the pack and attached it in a different spot to re-purpose it as a stand for the rig. Jury-rigging it with picture wire and a bungee, I set it up so that all I need to do is lift the top of the frame up, and the amp pretty much sets itself up! The bungee is there so that when I pick the amp up, it automatically closes.

This battery amp backpack feels REALLY stable, and with the benefits of the external frame’s hip support, there’s barely any weight on my shoulders. So my arms, shoulders, and upper back are all unencumbered when playing!

Total cost:

Used Vox DA10 amplifier	$100
Old REI external frame backpack	$25
4″ x 5/8″ mending braces	$3
Picture wire	$0 (I had this lying around)
Bungee	$0 (I had this lying around)

How would I improve this build?

Honestly, the Vox DA10 has some significant problems when running on batteries. When cranked up to high gain, it easily generates odd digital distortion noises that shouldn’t be in the signal. Maybe I need to replace the batteries, I’ll try that. But I can still run it fairly loud without the artifacts sounding TOO bad.

I want to use the space at the top of the frame to install a pedal board along with a better place for the iPod which plays my backing tracks.

I also want to improve the stand functionality a bit. The picture frame wire is surprisingly sturdy, but looks pretty hacky. I would like to put a couple of chains on it instead, which would look much better.

So if you see a wandering lit-up electric violinist playing out in the middle of the desert, be sure to stop and say hi!