Although the Raspberry Pi or RBPi has many exceptional qualities such as a small form factor, low price, low power consumption and credit card size, the single board computer is not endowed with a high fidelity onboard sound output. Therefore, to get high-fidelity sound, you must add a sound card to the RBPi. For all RBPi users who love music, HiFiBerry produces sound cards designed for optimal sound quality output.
HiFiBerry has two types of boards depending on whether you are looking for an analog or a digital board. If you have an analog amplifier, use the DAC board. However, if you connect to your amplifier via an optics link, use the Digi board. The standard RBPi kernel in the Raspbian distribution supports both the boards and they use Open Source software. HiFiBerry provides all drivers for both boards as open source. These boards utilize the P5 connector on the RBPi.
The HiFiBerry DAC is available as a Standard version with RCA connectors or as a 3.5mm phone jack version for headphones. Both are fully soldered boards; however, if you prefer to do some soldering, there is a DIY kit as well. For providing the best sound quality, these boards use a dedicated 192KHz/24-bit DAC from Burr-Brown. No cables are required, as the board connects directly to the RBPi, which also supplies it with power. Optimal audio performance is assured with on-board ultra-low-noise voltage regulators. Mechanical spacing between the audio board and the RBPi requires nylon spacers.
To connect the DAC board, you will need to solder an 8-pin header on to the RBPi, on its onboard sound connector P5. Now simply plug the DAC board in and start using it. The on-board ultra-low-noise voltage regulator will filter out all the noise from the RBPi power supply and you do not require any additional power supply or cable.
If your amplifier connects with an optical signal, use the HiFiBerry Digi board, which offers a high-quality S/PDIF output. The board connects to the P1 and P5 headers of the RBPi and supports up to 192KHz/24-bit resolution via optical (Toslink) and electrical outputs. The audio data streams produced are bit-perfect outputs, unmodified in any way.
The Digi board is also available in two versions, one with an isolation transformer and the other without. Although the hardware on the board is capable of DTS/Dolby Digital output, suitable software is required to make its full use. At present, HiFiBerry is not providing this software, but they will offer support to developers who want to implement this feature. The isolation transformer will provide complete galvanic isolation between the DAC on its output and the amplifier. However, most consumer-grade SPDIF connections do not require any output transformers.
For the future, HiFiBerry is planning a high-quality highly efficient stereo class D power amplifier to be connected directly on to the RBPi. Only external loudspeakers are necessary to get full 2x25W output power when driving 4-Ohm speakers with 44.1KHz and 48KHz sampling rates. This board will require an external power supply of 12-18V, but will power the RBPi as well, so ultimately only one power supply will suffice.
