This Holiday Card Features a Working Guitar Amplifier Built Into the Cardstock

Anyone who has ever been to a rock concert has seen guitarists playing in front of towering stacks of amplifier speaker cabinets. There are plenty of small portable guitar amplifiers on the market that are intended for practice sessions, but even they are at least as big as an average Bluetooth speaker. The envelope can, however, be pushed further. That’s exactly what YouTube maker Fran Blanche has done with her Holiday Card Guitar Amplifier that literally fits inside of an envelope.

Blanche is a musician in addition to being a maker, so this project fit perfectly in her wheelhouse. At first glance, this looks like any other greeting card. But there is a small speaker, similar to what you’d find in an audio recording greeting card, tucked into the cardstock. The speaker is very thin, and the cardstock itself acts as the driver’s cone to help amplify the sound. The speaker is, of course, just one part of a guitar amplifier, and Blanche still needed to create a circuit to take the line level signal that an electric guitar outputs and pump that up to a decent

That circuit was free-formed, and is built around everyone’s favorite low-cost op-amp: the LM386. Originally Blanche had planned to use a single op-amp to produce a clean signal, and that worked well. She then decided to add a fuzz tone effect using a second LM386 op-amp. The circuit is simple, and only requires a couple of capacitors that aren’t any thicker than the speaker. The ¼” guitar jack and 9V battery are a different story, and Blanche created a detachable dongle for those. The result is a completely functional guitar amplifier that easily fits into a typical holiday card envelope!