After I finished soldering all components and connected HiFiBerry USB to my Raspberry Pi I did some real-world tests.
The card is working, the sound is much better than the onboard sound if the Raspberry Pi. However I noticed, that the post-filtering of the DAC output of the PCM2903 is not very good. There are still a lot of high frequencies in the output. While nobody can hear these frequencies an active 2nd order lowpass filter after the output stage might be a potential improvement. There is still some noise on the output of the external voltage regulator. This needs further investigations.
The HifiBerry USB prototype is almost finished. Soldering the small TSSOP package of the sound chip is not trivial, but still possible with a good soldering iron, some solder wick and a magnifying glass. Unfortunately, I forgot to order the 12k resistor for the voltage regulator. For the tests, a combination of 10k and 2k in series will do the job.
First measurements look ok, all voltages are good, current drawn without USB connection is 12 mA and the oscillator is working. Therefore I think, that there are no major problems. Without USB connection, the onboard voltage regulator for the analog stage is disabled, therefore I couldn’t test it yet. Stay tuned for more information.
Do you develop audio equipment – amplifiers, preamplifiers, loudspeakers? Then you know that one of the most annoying things is the cabling of the different components: sound card, preamplifier, power amplifier, speaker and computer. There are some circuits on the internet that specializes in specific measurements. But now I found a project that created a universal measurement box for all kinds of audio measurements. Check out the project at Moxtone.com. Unfortunately no PCBs are available and the microphone input is only unsymmetrical. However, the block schema gives you a good overview to build something similar. I’m already thinking about a project that combines the whole stuff on a single PCB.
HiFiBerry is an addon-board for the Raspberry Pi. It will be connected to the board by USB. You can add it directly or using an external USB cable. To connect it directly to the USB port, the USB jack and the audio and video jacks have to be removed.
The PCB design for the HiFiBerry version 1 is almost finished. Due to the limited space, there will be no SPDIF in and out connection on the board. There is some space left for a pin header for these ports.
The circuit uses an external power regulator to provide the best possible audio quality. The audio chip is a PCM2906 which is known for its good audio quality.
After some failures (Jack was not running) I was able to use the Raspberry Pi as a audio-to-RTP bridge. A complete setup guide can be found on this page.
courtesy of Gijsbert Peijs
This project was started to transport the sound from my turntable to the loudspeakers without visible cables. Our flat already had ethernet in all necessary places, therefore the idea was to transport audio over ethernet.
I didn’t want to use large and expensive hardware for this experiment. Therefore the Raspberry Pi looked like the ideal hardware. It runs Linux and has integrated sound, network and USB. Unfortunately the sound hardware is unusable, because it does not feature an analog input. Therefore an additional sound card is needed. My choice was the Behringer UControl 202. It used the Texas Instruments PCM2902 chips that is well known, well-supported and good-sounding.
Stay tuned for more informations on this project.