+++
date = "2017-10-16"
title = "Signal 1 - DIY Audio Signal Generator (Part 1)"
tags = ["audio", "design", "electronics", "signal-1"]
description = "This is part 1 in a series of posts showing you how I build a digitally controlled audio signal generator based on the AD9833."
slug = "signal-1-diy-signal-generator-part-1"
+++

**Signal 1** is the name for my first _signal generator_ project. The goal for this project
is to create a device that can output clean sine waves in the 10 Hz - 100 kHz range for testing
audio equipment.

This is what I'm looking for:

 * 10 Hz - 100 kHz frequency range sine waves
 * Stereo Line level output (100-600 Ohm output impedance; 2Vpp) to feed directly into an amp
 * Display of frequency and other settings
 * Frequency presets or 'zero' at 1kHz
 * Adjustable amplitude (e.g. volume control; 5mVpp - 2Vpp)
 * Digitally controlled

Bonus features:

 * Reverse RIAA circuit 
 * Frequency sweep
 
There are at this point two pieces of hardware I have selected:

**AD9833 Programmable Waveform Generator** is a nice chip that can more than handle my simple needs. If
it can go up to a 16Mhz square wave, that'd be great, but not necessary. It's also inexpensive when bought
from China as a breakout board. I'm not usually a fan of there boards, but to for prototyping they should
be fine. The AD9833 communicates for SPI, so I'll need a microcontroller to handle that.

![The AD9833 Breakout Board](/img/signal-1-ad9833-breakout.jpg)

**Arduino Nano**. I was going to go for an onboard ATMega328 and program it directly using
_Atmel Studio_. However, there's so much good stuff out there for Arduino that I'll start out
by just plugging in an Arduino Nano and program that. The upside is that it alread contains 
USB/Serial so it's be rather easy to make this devise computer controlled later on. That said,
for the final build I might op to integrate the Arduino Nano components on my PCB anyway :-) 

For now, I've ordered a few AD9833 breakout boards from China and I'll start working on a block diagram
of the entire system soon, which you can read about in Part 2 of this series.