High end Audio Preamplifier controlled by Arduino

Here's my completed project: A high-end remote controlled preamplifier.

I wont go into all the audio side, if you are interested in that you can read through this thread here.

Basically I'm using an Arduino Uno to control a DAC8812 R2R MDAC IC (for an attenuator) and a MCP23S08 (for the input selector) via SPI. I'm also using a Adafruit NeoPixel to show volume level and mute by colour. I didn't want to use an LCD display, I think unless implemented in a very high end aluminium enclosure they look tacky.

Inputs include a high resolution encoder (128PPR) and IR.

Features written in Arduino code:

  • Changing of volume, input and mute via Apple remote and encoder
  • Periodic saving of volume level to EEPROM (limited to every 60 seconds, only if value has changed)
  • Fading to previously set volume after power on
  • NeoPixel fades from blue to red as volume increases
  • NeoPixel flashes when changing inputs
  • NeoPixel flashes green when mute is enabled
  • Startup and power off mute to avoid pops/thumps
  • Different volume increments for encoder and remote
  • A debug boolean to print information

I've never coded anything in C before so not sure if my code is optimal but it works great and is very responsive to use. It's attached in a zip file.

Thanks Arduino!

preamp.zip (24.8 KB)

And here's a GIF of it in action:

You don't have any schematics for the audio circuits in PDF format ?

Nope. They are all in Eagle PCB format if you follow the link to the DIY Audio forum.

I thought Eagle had the ability to make a schematic in a format that you can read with Windows without Eagle installed .

Always release schematics as a readable format - not all people have Eagle,
and those that do don't all have the same version even. Export as Image, 300dpi
resolution seems to work reasonably well.

Like I said in the first post, if you are interested in the audio side then follow the link to the DIY Audio forum. There you will find all schematics in jpeg as well as the Eagle PCB files :slight_smile: