Tuesday, November 15, 2016

Rpi Zero w/ Two Different Inexpensive USB Audio Cards

Rpi Zero with a Generic Low Cost USB audio Card & Zero with USB and a PCM2704 chip from Texas Instruments.

Lowest cost Rpi audio solution I have found is using the Zero with a inexpensive wifi card and a USB music card, total cost $10. I found audio popping with this scenario. But at a slight increase to $11.50 the sound quality is much nicer using a USB with the PCM2704 chip from Texas Instruments. Both options require additional $'s evaluation for microsd card and power supply. My friends at the Raspberry Pi Discussion Forum turned me onto the PCM2704 low cost USB card that in my opinion outputs nice acceptable sound quality (thanks clacktronics for the suggestion).
MoOde software over wifi from Rpi Zero powered USB hub w/PCM2704 audio.
USB is complicated here, but will be simplified. Zero has a camera too.
Inexpensive USB audio, PCM2704 on bottom; both work on Zero w/MoOde, hot swapping is OK
I will be reducing the USB wiring by soldering the wifi and USB audio with PCM2704 in place above the zero, then put into a small case with power input and audio output jacks showing. My initial attempt to reduce the USB Hub was a complete disaster, disassembling the case and trying to solder the USB Audio card to the USB Hub did not work for me, mostly due to my poor soldering capabilities.
The USB Hub which was destroyed by trying to attach the USB Audio directly.
My goal is to get a tiny package, something like a tic tac container. As you can see, the Rpi0, USB Audio and wifi can easily fit except the USB Hub isn't there.

A pi Zero running v3.0 MoOde used 5.16V and 0.19 amps which is 0.98 watts running a USB audio card and a wifi dongle through a USB hub. While starting up this used more power for a very short period of time. 1 watt powered the pi Zero headphones, slightly higher when performing wifi interactive communications. The Rpi3 used 0.26 amps or 1.35 watts for the same functionality. 
Solar powered w/Li-ion battery, Rpi0 with USB Audio, wifi and small speaker.

This tiny solution would enable an inexpensive car audio system controlled by a cell phone. Or just listen with headphones. 

The comparison of these USB audio systems needs to be compared to a Google Chromecast Audio because the Chromecast has great functionality with lots of audio software. Other very low-cost solutions exist that don't have an amplifier including the items in the photo below (counterclockwise from the top: Rpi0, USB audio card, USB audio card with optical SPDIF, Chromecast Audio with analog and optical SPDIF).

The Chromecast Audio puck is $25 US and has the functionality of a wifi enabled Rpi with audio output, similar to the Rpi0 and USB SPDIF output card shown above. There may be audio quality differences. Through software, I am thinking that the USB audio can be configured to mimic the Chromecast Audio functionality. This may require some skilled software people. It is quite easy to connect many audio services to the Chromecast Audio puck.

The audio evaluations has been broken out into the following audio sections:

And a related post, Uniqueness of the Rpi.

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