DAC—FAQ
DAC—FAQ
Functionality
Q: What is it?
A: The DAC is a high-quality digital-to-analog converter for the Raspberry Pi. It is like a sound card. However, as it was designed for optimum audio playback, there are no audio inputs on the card.
Q: Can I connect my loudspeakers directly to the HiFiBerry DAC?
A: The DAC is only a digital-to-analog converter. You need to connect it to an input of your existing amplifier.
Q: But what about headphones?
A: HiFiBerry DAC does not have an integrated headphone amplifier. So even for headphones, you need an external headphone amplifier. A very cool DIY project that we like is the CMoy amplifier.
Q: Does it have any audio inputs?
A: The HiFiBerry DAC is only a digital-analog-converter for audio output. We decided to use a DAC-only chip to provide the best audio quality for audio playback. This comes at the expense of functionality. Therefore, there is no audio input.
Q: Can I still use the GPIOs? It seems they are blocked.
A: On the HiFiBerry DAC+ you can solder a 40-pin header onto the DAC that allows you to connect to the GPIO header. Note that some of the pins are already in use by the DAC, so you can’t use them. But there are still plenty of GPIOs available. On the old HiFiBerry DAC, the GPIOs are not used, but the header is already soldered. If you want to use a stacking header, you have to de-solder the GPIO header. (Note that soldering/de-soldering on our boards voids the warranty. We recommend it only to people who have a lot of experience, as we’ve seen several boards that were damaged during soldering.)
Q: Does it have a volume control?
A: Our new HiFiBerry DAC+ board comes with an integrated volume control. However, the older HiFiBerry DAC uses the digital data without any post-processing. It will output the sound stream with the volume the application feeds it. Many applications can use an internal volume control (so-called software volume control). If the application you want to use doesn’t have a software volume control, you can’t control the volume by software. However, the best way to control the software is a analog volume control after the DAC. While software volume control is an option, it will reduce signal-to-noise ratio. If you connect the DAC to your amplifier, you should use the volume control of your amplifier.
Performance
Q: I don’t see any external power supply. There aren’t even large electrolytic capacitors on the board. Powering the DAC directly form the Raspberry Pi must be very noisy. Isn’t this a problem?
A: We use an ultra-low-noise voltage regulator to create a very clean power supply for the analog part of the circuit. Instead of large electrolytic capacitors, we use small X7R capacitors. These capacitors have a very low ESR. In our experience this works very well. In our measurements, noise levels were less than -115dB when the Raspberry Pi was using WLAN.
Soldering/Mounting
Q: Does it work with all Raspberry Pis?
A: You need to check that you have the right Raspberry Pi. The new DAC+ works only with the Raspberry Pi model B+, while the old HiFiBerry DAC works only with the older Raspberry Pi model A/B hardware Release 2. To make sure, you have to identify the P5 header on the Raspberry Pi board. Look at this page for how to find this connector.
Q: Do I really have to solder something onto my Raspberry Pi?
A: If you use our HiFiBerry DAC+ on a new Raspberry Pi model B+, you don’t have to solder anything. Just plug it onto the Raspberry Pi. You only have to solder a connector if you’re using the old HiFiBerry DAC on an older Raspberry Pi. Unfortunately, the pins needed for the sound connection are not populated. However, soldering is not very difficult, even for beginners. Check out our page on soldering the connector.
Software support
Q: Does it work with my Linux distribution?
A: Since December 2013, the HiFiBerry DAC driver is included in the newest Linux kernels. However, many distributions use older kernels. If you use Raspbian, you can get “rpi-update” to update to the latest kernel that already has HiFiBerry DAC included. The HiFiBerry DAC+ driver is included in the August 2014 release of the Linux kernel. Check out our software page for more information.
Q: Are there any distributions that work with the HiFiBerry DAC out-of-the-box?
A: Many distributions support HiFiBerry DAC out-of-the-box. Have a look at our software page.
Q: Which modules do I have to load in /etc/modules?
A: Have a look at our software configuration guide.
Q: How can I use volume control in application XXX?
A: Unfortunately, it’s very different for each application. Please contact the developers of the software to find out what you have to do.
Other questions
Please have a look at our community forum for further questions.