Usage

What could I do with RPi-DAC?

If you operate RPi-DAC with a Raspberry Pi (RPi) you can do:

• Use the RPi as SD Card Player
• Use the RPi as network player, e.g. to listen to Internet Radio Stations
• Use the RPi as DNLA server, as media server: install XBMC and enjoy your home media sources
• Install Volumio as your network player
• run RPi as bare bone system and create your own audio system

What else is needed?

If you get just the RPi-DAC board - just a transformer (AC) is needed (and RPi).

Any transformer, at least 50VA, optimal 100VA (e.g. Toroid) is fine with 2x15V AC out (without center tap!). Just to make sure the transformer has two separate coils, no center tap.

You need all the cables, e.g. to connect and operate the Raspberry Pi or an USB, TOSLINK or S/PDIF cable

Remark: if you want to connect a PC which does not have S/PDIF or TOSLINK - there is a nice electrical S/PDIF adapter:
Halide Design"

Connecting an iMAC: you need the RPi-DAC-SPDIF module and a TOSLINK cable

How to set the loudness?

You can use the Software Loundess Control. Such one works by dividing the DAC values before they are sent to the DAC.

It works but on lower loudness it decreases the SNR.

The best results you should get if:

• use a headphone loundess control unit (a trim device which attenuates the headphone signal inserted in the output path)
• set the source loudness, e.g. the PC loudspeaker icon, to 100%
• run always with the highest signal possible to feed the DAC before you realize a signal distortion
• trim the signal at the output (not very efficient but better quality)
• where you have the option (e.g. Volumio): select Hardware Loudess Control and use the approach above

For FPGA pojects - is there a clock reference?

If you want to operate the RPi-DAC, T-DAC, for instance on your FPGA system and you want to have an accurate clock source for the audio processing - there is an option to solder an 24.765MHz clock oscillator.

This one can be used as a master clock source with very low jitter (2.5ppm).

Could I use modules for other projects?

Sure, you can. The RPi-DAC system was designed with the approach of high modularity, to combine modules in different ways and to use for other projects and purposes.

It is possible to use these modules as separate boards for other projects:

• RPi-DAC-SPS - a switched DC power supply unit for four rails, output voltages can be adjusted, 3 rails with common ground plus 1 rail for negative voltage (without common ground)
• RPi-DAC-SPDIF - a S/PDIF and TOSLINK module, where also an XMOS USB can be connected, used to convert inputs to I2S signals (etc. for other DACs)
• RPi-DAC, SingleStereo - a DAC module with I2S input which needs 3 power rails (7V, 2x16V) and generates analog headphone output signal