About this project
Audio Injector Raspberry Pi Sound Card
Our challenge was to give you a well designed high quality audio sound card at an affordable price. The Audio Injector is perfect if you want to do an audio project with your Raspberry Pi, whether it requires audio input, output or both. (new update - a headphone jack has been added - and an inbuilt microphone - see the updates for more info).
Providing physical input and output volume controls, very nifty if you want immediate control of the sound level without having to flap about in software.
Audio injector now comes standard with a headphone jack.
You can also optionally choose to add an inbuilt microphone. Choose the pledges carefully to ensure you are getting the correct version ! The following video was recorded with the first prototype usnig the inbuilt microphone.
Back to the headlines ...
Need audio input for your home automation project ?
Need voice commands for your Kodi (XBMC) or OpenELEC medicenter ?
Need analog input/output for your radio project ?
Need analog input and output for your Karaoke project ?
Need high quality audio input and or output ?
There are so many different projects which you can create using this sound card - audio to and from almost any of the devices on the Raspberry Pi, such as disk, USB, HDMI, WiFi, the ethernet network and so on.
You can put the audio injector into an already existing audio setup by splicing it into a sound path. It is simple - plug into the audio injector and plug out again. The original audio can be put straight through. If a straight through isn't what you want, then use the ALSA mixer to turn off the bypass.
It's all about your projects.
We want to enhance your projects, with great quality audio. We also realised that as part of enhancing your projects we had to ensure you can still stack add ons and hats whilst including sound (from the Audio Injector sound card). This is exactly what can happen - you can plug other boards on top of the Audio Injector sound card.
The Audio Injector sound card is designed to keep the same PCB profile of the Raspberry Pi, with the PCB edges and GPIO header in exactly the same place. This means that your current add ons and hats will still plug into the Raspberry Pi keeping the same profile, just a bit taller!
Voice command: Perhaps you want build a voice activated home automation system. This will utilise the input audio functionality of the Audio Injector. Check the pledges which include inbuilt microphone.
Audio input : Do you require a microphone input for a home automation or radio project ? Some pledges come with the suitable sound card and dynamic microphone preamp.
Spectrum analyzer : Plug a microphone preamp into the input audio lines and use jackd with brianalyze. You can also purchase a microphone+preamp pledge here which will provide some of what you need.
Karaoke: Plug in a Flatmax Studios Micromixer and a microphone and you can enjoy instant Karaoke !
DLNA and Airport express player: using the output audio functionality of the Audio Injector, you can easily setup a DLNA player. This will let you play music from your phone wirelessly or over the network.
Phone applications : As you have both input and output of sound, you can use phone software with the Audio Injector Sound Card.
LED audio display: Capture the audio and send pulses over the gpio pins to leds. Pipe the audio straight through to the output with zero latency - using the bypass functionality.
Microphone: Inbuilt electret microphone with mixer controls. Allowing voice control or other applications.
Headphones: 50 mW max power into 16 ohm and 30 mW max power into 32 Ohm headphones (check the updates to see more)
Driver : ALSA
Latency: As low as 0.54 ms in or out (that is 540 microseconds !)
Linux : Already integrated into the Raspberry Pi kernel. If you have an older version of the kernel, simply run "rpi-update" if you need to. Edit /boot/config.txt and set dtoverlay=audioinjector-soundcard
DAC and ADC : 96 kHz, 32 bit audio.
Analog Voltage : 3.3 V rail to rail. Separate linear supply to reduce noise.
GPIO : Standard 40 Pin header, broken out above the add on card to accept more add on cards and hats.
Some of the pledges include mixers available from Flatmax Studios, check on Amazon and Ebay for these products. These mixers allow you to mix down balanced lines going into or out from the Audio Injector sound card.
Other pledges also include one or two professional grade performance dynamic microphones. These pledges are at a very reasonable price for the quality of the products.
Some pledges include the addition of the inbuilt microphone.
The Audio Injector sound card has been tested both in this and other projects, yielding many different prototypes along the way. The images show one of the prototypes which have been tested. These prototypes allowed the development of the Linux Kernel machine driver for the Audio Injector and the Raspberry Pi.
Several prototypes have been refined over the last month, the latest supporting headphone output. An even more recent one has now tested the addition of the electret microphone directly to the board.
Risks and challenges
We have been manufacturing hardware for around 10 years and are well versed in the various issues and pitfalls which come with the manufacturing trade.
For quality control purposes, each Audio Injector sound card will be tested on a Raspberry Pi before shipment.Learn about accountability on Kickstarter
For me, very loud ! It is a subjective thing, however when I use my 32 Ohm headphones (over the ear isolating DJ headphones) I have to reduce the gain by -18 dB (eight times reduced levels) to make it approach a comfortable listening level. I find anything above that very loud.
If you were to use 16 Ohm headphones, then it would be a reduction of sixteen times to make it comfortable !
NOTE : there is enough power out of the headphone socket to damage your hearing. Please look after your hearing and if you listen to music loud when using headphones, do it for very short durations, such as one song only.
Nope - The audio injector is already integrated into the stock standard Raspbian Linux kernel. To install, simply get the latest kernel (rip-update) and then add one line to your /boot/config.txt :
This one line will load the Audio Injector sound card driver at boot time automatically.
USB sound cards start to stutter when the cpu or USB lines are heavily loaded. An onboard sound card is far more robust and doesn't have the same problems. This is because the ARM processor on the Pi has specialised "i2s" and "DMA" engines implemented in silicon, which levarage a huge amount of the heavy lifting away from the software.
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