The circuit inside the megaphone is a cheaply built audio processor. It’s designed to make a child’s voice sound like a robot, spaceman or alien…whatever that means. Basically it’s a pseudo ring modulator with three different settings.
The most dramatic modification done to the megaphone is the addition of a pitch adjustment (see the diagram below for details). Most of the other modifications are interfacing hardware. On some models I’ve installed a feedback button. This just feeds the output back into the input. The pitch of the feedback squeal can be changed with the pitch adjustment. I’ve also installed input and output jacks on all models. This lets you feed any sound you want through the processor.
This piece uses two sound circuits: A three setting sound processor (already installed in the megaphone), and a strange, alien baby circuit. When the baby circuit is glitched, it outputs a random sequence of modulating tones. Because these tones are simple wave forms, they work especially well with the phone’s relatively low quality processor. The two combined circuits and the addition of a 1/4′ input for processing external sounds, make this a powerful and diverse little unit. Click here to view a detailed diagram.
The megaphones factory installed controls and features are:
- spring loaded power trigger
- sound processing selection switch
The added controls are:
- main power switch – This was installed mostly to avoid accidental triggering and needless battery drain during transportation.
- power trigger hold switch – The ‘phone’s original design required that you hold the trigger in order for it to receive power. This can have obvious drawbacks , so I installed a switch to serve the same purpose. The trigger still functions normally if the switch is off.
- feedback button – Makes screeching feedback that can be adjusted with the pitch control.
- Switching 1/4″ output jack – turns off the megaphone speaker when a cord is plugged in.
- 1/4″ audio input jack – Any sound can be fed into the ‘phone to utilize its lo-fi processing functions.
- pitch – Raising the pitch all the way to its peak and quickly back down again will often cause the random note glitch.
- talk button – Triggers a variety of phrases.
- feeding button – Makes an unnatural suckling sound.
- Power reset button – Sometimes needed to reset the circuit if it crashes.
- baby speaker – This is a crude but effective solution to a problem I had wiring the baby out directly to the phone mic. An advantage to this method is that it allows more control of the sound as it goes into the mic. It can even be used like a talk box, where the speaker is placed close to or even in your mouth, which filters the sound.