Stupid Pedal Tricks

Blinded by the light!

Okay, so this one needs a little back story: I built a vacuum tube-based Vibracaster, which is a neat little tremolo circuit designed by Rick Holt.

While vacuum tubes in guitar amps might heat to the point of glowing, the voltage, etc. in this pedal is no where near enough to cause that, so in order to get the fun glowing tube look, I inserted an LED into the bottom of it. For extra fun, I used a blue one. I have it set up so that the glowing tube also serves as the on/off indicator. (continued below video)

This is the style of LED I installed in the base of the vacuum tube.

For size comparison.

One problem with this is that you operate these things with your shoed foot and there’s this somewhat fragile glass tube sticking out, so I took the metal shield and drilled various sized holes in it for a slightly psychedelic look and painted it to match the enclosure. The holes would permit the light to shine more visibly with the shield on.

While the LED was plenty bright without the shield, it was still pretty dim with the shield on. It would probably be perfectly fine on stage under low light, but it still got me thinking of something fun to do :)

I wanted to see if I could go Clark Griswold Christmas Lights on this bastard.

Not pictured: the Vibracaster in a manger, centerpiece of the nativity scene.

I needed it to work so that without the shield it was exactly as it already was, so attaching anything directly to the vacuum tube was out, plus it would look tacky (ha! too late!). I decided the perfect way to do it would be to have the extra lighting inside the shield so when it’s on, they’re there, when it’s off, they’re not there.

Well, that shield and tube leave very little room between them, certainly not enough room for the LED pictured above, much less several of them.

The solution? SMD (surface mount) LEDs!

This is an SMD (surface mount) LED. See how itty bitty it is? Look, there it is compared to the tip of a Xacto blade and then compared to the standard LED mentioned above.

But what is SMD (surface mount)? Well, I, and other pedal builders (disregarding mass-produced factory pedals) use “through hole” components. You stick those little legs through the holes in a circuit board and solder them on the back of the board. They are small, sure, but still easily handled. The design is convenient-ish for a human to be able to reasonably work with it by hand.

SMD stuff, however, is tiny, because it can be. Resistors, capacitors, transistors, other kinds of diodes, etc. all come in SMD form. These are generally too small to be reasonably handled. Typically if you drop one, forget it, especially on carpet. Your’e never finding it. The reason for the teeny-tiny-ness is that the size of circuit boards can be drastically reduced and because machines are going to be installing and soldering them, and machines don’t get the butterfingers, nor care how small stuff is.

So I bought about 20 little blue SMD LEDs. They are bright as hell!! Keep in mind, however like most electrical components, there is power and ground which have to be wired right in order to work, except these have damn near microscopic little exposed areas of metal to connect a power source and ground wire.

It’s a proof of concept, okay? It ain’t supposed to be pretty.

Second jack added (in black to avoid confusion) for the removable shield and light show.

I painstakingly underwent the torture of sticking 6 or so SMD LEDs to a piece of tape, getting little strands of wire soldered to them, 2 connection each: a common power source and common ground, and then connecting those to the main power source (the pedal’s power supply).

Using a hot glue gun, I stuck the little LED network to the inside of the tube shield using a few dabs of hot glue. I then added a second 9v-style DC jack pushing 9v through a 1.8kOhm resistor (to limit the voltage to a safe level for LEDs, as 9v will burn them out instantly) and connected the wires from the shield’s LEDs to a 9v-style barrel plug, so I could plug and unplug to remove it completely. This, of course, required opening the pedal, drilling another hole, and wiring the second DC jack to the the same power bus and ground as the tube’s LED, so that the foot switch tuns all of the LEDs one and off.

This is what you see in the video, first without the shield (just the one LED in the vacuum tube), and then with the shield and added LEDs engaged in retina-scarring luminescence.

It’s goofy and impractical, but fun to try out, and the basic idea might be applicable to future needs.