At one point or another every aspiring electronic enthusiast builds a Schmitt trigger oscillator to generate audio frequencies. For me it was no exception and that’s what fueled my interest in electronic music instruments. In 2006 this GetLoFi post was published detailing a simple oscillator circuit that worked fairly well as a rough starting point. Today the same basic idea is available in kit form and as a hand-built pedal from GetLoFi.com/shop for everyone to enjoy the crunchy square wave oscillation and modulations.
Surely anyone can build a similar circuit with a few Radio Shack components however the are some nuances for making a great sounding oscillator. First off tame that output if you are using a 9 volt battery to power this circuit, the hot output will be too distorted and dangerous for the amplifier. To make things quieter simply add an electrolytic capacitor 1uF or greater with the – side towards the output and a 1K resistor following in the series. Then bridge the output pins from Ground to the Tip with a 100 ohm resistor. This attenuates the output by dumping some of the signal towards the ground.
The second tip is ALWAYS use sockets for your IC chips, even if the chip is not expensive or you are in a hurry to finish a project. This will help down the line when for some reason the IC stops working be it from overheating, a short, or applying the power to the unit backwards. It is a million times easier to fix something by simply popping the IC out and replacing it with a new one, then going through a de-soldering nightmare, especially if you are working on a Through-hole board. Virtually all GetLoFi Kits are surface-mount making it easier to correct an error and replace a component.
The final tip for building oscillators and other devices that run off 9 volts is include a Boss-style DC Jack. It means that the DC jack is 2.1 mm with Tip ( – ) negative wiring. Please note that the assembled 4093 Quad Oscillator Pedals do have this feature. Having a DC jack liberates your pedal more in conjunction with the internal battery. Surely you can still use the 9 Volt clip, however now there is no worries about the device dying in the middle of the show or a recording session. There will be no changes in pitch and operation from the sagging battery voltage. Also no need to remove the backing in order to swap a $3 battery when the power switch gets accidentally gets left on. As an added bonus the power jack can be used as a Gate of sorts for the device. With a 555 or the LoFi Sequencer acting a power source to drive the 9 volt entire circuit, so by connecting their outputs to a DC jack you can instantly add a pulsing feature.
In closing we hope that all those tips help you when putting together an electronic device made to last. For those who do not feel comfortable searching around for all the correct parts and stressing over confusing schematics, please try out one of our simple to assemble Kits. They include circuit boards and all the parts needed as well as step by step photo assembly assistance. The Quad Oscillator pedals are also now available from the GetLoFi.com/shop. Enjoy.
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