Cardia DSP

September 2024

Software DSP is used to implement active crossovers, FIR and IIR filters, as well as adjustments to delay, gain for each channel.

There are a number of aspects that need to be considered:

  • Samplerate, e.g. 44.1/48khz, 88.2/96khz or 176.4/192Khz
    • Bit depth e.g. 24, 32 bit
      • Platform e.g. macOS/CoreAudio, Windows/WASAPI or ASIO, or Linux/ALSA or other
        • Communications interface e.g. PCIe, USB, Firewire
          • Protocol e.g. USB, Dante, AVB, Ravenna/AES67
            • No. of channels, e.g. 32
              • FIR length, e.g. 64k, 128k, 256k
                • DPS Software, e.g. CamillaDSP (macOS, WIndows, Linux), Brutefir (Linux), JConvolver (Linux), or proprietary software (AcourateConvolver) or built into music player software (JRiver, FooBAR).

                  DAC

                  I decided to use a single 32ch DAC, not attempt to synchronise 4 x 8 channel DACs - although that's still an active line of investigation for the future (more on this later).

                  I considered the Tascam ML32 (Dante) but at the time Linux support was tricky. This has changed recently with PCIe cards available for Linux (e.g. from Marian).

                  I was drawn to use an AoIP architecture, so that playback and capture devices could be integrated via network attachment and routing, providing more flexibility than looking for a single device.

                  The final choice was AVB based, via:

                  • RME M32 DA Pro
                    • RME AVB Tool
                      • RME Digiface AVB

                        TBC