While we have previously discussed how to get the best sound out of a standard Raspberry Pi, there is only so much that you can do with the device's limited on-board audio. If you want higher-quality sound, you will need to add a separate audio card to your Pi. These cards are generally added as HATs (hardware added on top), and a handful of competitors offer the cards. In addition to audio processing, these cards all include a quality digital-to-analog converter ("DAC"). Interestingly, nearly all of the competitors in this space use the same underlying audio chip - the Texas Instruments PCM512x. As a result, while all of the HAT boards are a huge improvement over the stock Raspberry Pi, none of them sound notably better than any of their competitors. Just from amazon, you can find the following DAC choices that use the standard PCM512x chip:
Similarities Between all of the DACs
All of the cards are standard HATs that snap on top of your Raspberry Pi without any soldering or other complexity. Raspberry Pi HATs all share a handful of similarities. First, there is no soldering - all of these boards simply plug onto the top of your existing Raspberry Pi board. Second, the mounting holes for the HAT will line up with the mounting holes already on the Raspberry Pi. Additionally, these boards will typically come with spacers so that you don't over or under tighten the HAT onto your board. Lastly, the HAT will use an EEPROM module on the board to identify itself to the Raspberry Pi. It tells the Raspberry Pi which IO pins it is using, how they need to be configured and what drivers have to be loaded. The cards above also all use the Raspberry's power supply to draw power without requiring a separate wire. In other words, installation for all of these cards is completely straight-forward.
Since all of the above cards use the same underlying Texas Instruments chip, they share many of the same audio features, too:
- Register-Selectable Audio-Processing Functions up to 48-kHz
- Dynamic Range Control (DRC)
- Equalization (EQ)
- DAC Functionality to 384-kHz fS
- Market-Leading Low Out-of-Band Noise
- Selectable Digital-Filter Latency and Performance
- No DC-Blocking Capacitors Required
- Integrated Negative Charge Pump
- Intelligent Muting System; Soft Up or Down Ramp and Analog Mute for 120-dB Mute SNR
- Integrated High-Performance Audio PLL With BCK Reference to Generate SCK Internally
- Accepts 16-, 20-, 24-, and 32-Bit Audio Data
- 1.8-V or 3.3-V Failsafe LVCMOS Digital Inputs
- Integrated Power-On Reset
The HiFiBerry DAC Products
While all of these DACs are similar, we're talking about the Hifiberry HAT's today. These cards are, at the moment, either similarly priced or cheaper than many other brands, and the brand is well-established in this space. HiFiBerry also offers a line of cards for all types of setups (digital output, RCA jacks, with and without an amp, etc), and they offer a few different price points depending on which features you might find important. In addition to the pro model linked above, they also offer the HiFIBerry DAC+ Standard and HiFIBerry DAC+ Light models, which can get you down to as cheap as half of the price of the Pro model. As a result, you will likely find an appropriate HiFIBerry DAC no matter what your budget or setup happens to be.
This pro board, like the others above, is based on the TI/Burr-Brown PCM2122 DAC chip. The board is connected to the Pi through the 40-pin GPIO header, and communications are through I2S, an audio communication standard. It works almost out of the box with Volumio2 and a guide exists for a quick setup with other audio servers, such as the MPD/Mopidy setup that I am using at home.
Generally speaking -- and perhaps I'm just not sophisticated enough -- most of these DACs are rather similar. They all provide excellent sound quality when compared to the standard Raspberry Pi, and, especially when going with the HiFiBerry line, there is probably an option for nearly every budget. If you find the Raspberry Pi's audio output insufficient after using an audio setup such as the ones that we have discussed here previously, I highly recommend purchasing one of the above DAC boards prior to giving up on the project.