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Simple Digital Noise Generator

Matt 0 Comments

Here’s a little noise-making circuit I’ve been working on. It has a sound reminiscent of vintage sound chips, such as the AY-3-8910.

It works by using a D flip flop clocked by a 555 timer to sample and hold the signal from a ring oscillator. The high speed and frequency instability of the ring oscillator (close to 4 MHz) makes an ideal noise source, and the variable sampling frequency affects the frequency content of the noise.

This is a good example of the Nyquist theorem in action. As the clock rate of the 555 is lowered the high frequency content of the noise disappears. There is naturally a lot of aliasing, as this is a 1-bit signal, and there is no reconstruction filter on the output, but the frequency roll-off is still clearly audible.


Parts list


CD4070 XOR Gate (IC1)
NE555 Timer (IC2)
CD4013 D Flip Flop (IC3)
LM386 Audio Amplifier (IC4)


1 kΩ
1.5 kΩ
10 kΩ
100 kΩ Log. Potentiometer


10 nF (x2)
220 µF

Planning circuit layouts with DIY-LC

Matt 0 Comments

At some point there will be an Arduino project that is just too good to take apart. You can’t leave it on the breadboard forever, but building a circuit on prototyping board can be confusing for beginners.

The best way to make this process easier is to plan the layout of your circuit before you start building. I used to use graph paper to do this, but then I found a great free tool called DIY-LC.
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Arduino Tip: 7 segment LED display with 4094 shift register

Matt 0 Comments

This is my first Arduino example sketch – hopefully the first of many.

This sketch allows you to control a 7 segment LED display using an Arduino and a 4094 shift register. Only 4 data pins are used on the Arduino, rather than 8 if you were to control the 7 segment display directly. For this example I used a common cathode LED display.

Simply copy the code below into the Arduino IDE, build the circuit explained in the notes and watch the numbers count up.

Arduino 7 Segment Display

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Welcome to Matt’s Music Tech!

Matt 0 Comments

Over the next few weeks I will be migrating from my old website, Totally Keyboard, to this brand new, self-hosted site. I’ve had a few problems with Blogger over the last year or so, and I figured it’s time to get started on something new, and here it is!

I started Totally Keyboard way back in 2009, and although I have enjoyed building up the site I feel like it’s time for a change. It’s going to take some time to populate the site with all the old goodies from TK, but I’ll be able to add a lot more content – and all of the old download links will continue to work even when the migration is complete. Right now I’m just focusing on getting the site working, but soon enough I’ll be posting new content, as well as some of the best posts from TK.

Sit tight folks, this is gonna be a bumpy ride!