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The Tremolo Tube: The goal of this project was to first create a small amplifier that could handle a line input and power a small 3 1/2" speaker. This sound would be directed through a chamber of sorts... in this instance a 4" PVC pipe, and the unique qualities of the amplifier, speaker, and piping will create a unique timbre for any sound passing through. In addition, at the end of the pipe i planned to have a mechanical rotating baffle of sorts whose rotational speed i could fluctuate to create a tremolo-style effect. This sound could then be recorded, sampled, mangled, discarded, or whatnot. Below are some of the steps, comments and the outcome.

The first thing I needed to do was gather some parts. I had some spare speakers from an old wooden upright Fisher Stereo which had ceased functioning years ago, so I grabbed those.... picked up some 4" diameter PVC pipe, some end caps, and lock nuts from Home Depot. All this cost no more than $15.

Here are a couple pictures of the first steps. I had marked off four holes on the end cap to align w/ the mounting holes on the speaker. Drill. Screw. And that's that... it already looks like something. I needed to tidy up the excess screws so I trimmed off the ends with a Dremel. The picture of the screw ends is actually of them melting the nylon in the rug. That eventually cost me when I moved out. Regardless, it starts out clean and compact.

Here we've got the beginnings of the amplifier. With a little homework I was able to easily find dozens of schematics on the internet for various types of simple amplifiers. I just grabbed a few, compared, and moved ahead. I had most of the resistors and caps floating around but I needed an op amp so I gutted one of my six Gemini PMX 60s. I love these mixers, not because they sound particularly good or have exceptional features, but because you can buy them for about five bucks on eBay and spare electronics always come in handy. Anyway, boxed in yellow is the op amp I grabbed. It was no Burr Brown but it did the job.

Here you have an example of my poorly planned layout and sloppy soldering job. Fuck it though, it worked. Next I had to squeeze it in the PVC end cap which, required a bit of trimming and wiggling. Eventually i think one of the bolts had to be permanently removed. In the end however it all fit in nicely and it wasn't damaged in the process.

I wanted to add in a power switch, the input jack, and a volume control so I grabbed the Dremel and started hacking away at the PVC end cap. Because of the limited space some care had to be taken to carve out room for the pot and knob. And of course... a bright ass LED to let you know that the sucker is fired up.

What I had planned on doing was running a shaft through the PVC pipe along its diameter. This shaft would be secured by bearings which would allow it to rotate smoothly, quietly, and easily. The shaft would be turned by a motor with a speed control. Attached to the shaft would be a circular baffle which when spinning would open and close the end of the pipe. So here you have a shot of the bearing, the shaft, the hole in the PVC pipe and the motor with my hand made pulley-type-thing.

So here's the nearly finished project. A lack of additional materials, a lack of desire to make another trip to Home Depot, and a lack of ideas to fix a design flaw ultimately lead to the build of this machine stopping here. The biggest issue was I couldn't get the shaft and bearings square so it was very difficult to rotate the shaft. My small 18V motor just couldn't do it. And I hate to admit it but my amplifier wasn't enough to drive that speaker well enough to move a significant amount of air down the pipe. So this stopped here. It's too bad too because this thing ended up looking bad-ass.