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HILO edited this page Jun 24, 2022 · 10 revisions

Welcome to the FreeDSP_Catamaran_AB wiki! Stereo Image

Overview

FreeDSP Catamaran A/B board is a DSP board that uses ADAU1701. A mono construction board enables to the improvement of the sound performance and programmable size of the DSP process.

Ordinary ADAU1701 Embedded ADC-DAC Overall Distortion: Single End Ordinary ADAU1701 ADC

FreeDSP Catamaran A/B Differential ADC-DAC Overall Distortion: FreeDSP Catamaran A/B ADC to DAC DIstortion

Design Concepts

This project will be sticking to the following concepts.

  • Use the ADAU1701 embedded codecs.
  • Get the best sound performance from the ADAU1701 embedded Codecs.
  • Dual-mono construction stereo linked equipment design. (Minimum crosstalk)
  • Against the GND level problems. (Especially for Unbalanced RCA-pin Cable users)
  • Simple onboard design.
  • A/B selectable boot feature for the easy firmware tuning/modification trial.
  • Single-Wall Power supply (DC12V)
  • Use the SMD parts basically, but use through-hole caps for the audio path.
  • Anti-pop Circuity
  • 10cm x 10cm size PCB

Features

  • 1in4out RCA jacks on each PCB (2 boards requires for stereo use)
  • High-Performance Differential monaural input ADAU1701 ADC circuit
  • GND lift-able Differential RCA-pin Input circuit (Tie to GND Jumper-land is provided)
  • GND lift-able Differential RCA-pin Output circuit (Tie to GND Jumper-lands are provided)
  • A/B Selectable Dual boot EEPROMs
  • A/B Program Select toggle switch
  • Common-mode Choke filtered Power Supply Input
  • 0805(2.0mm x 1.25mm) SMD Resistors & Capacitors
  • Through-Hole Ele-Caps on the critical Audio Path
  • Unity Gain Analog Audio Input and Output (2V RMS)
  • Absolute Phase transparent. (No need to invert Output Phase)
  • Power-ON/OFF/Reboot Anti-Pop Audio Mute
  • Buffered TDM Interlink I/O Header (with Enable control)
  • Rotary Pots x4 for AUXADC
  • Mains Power Switch
  • Reset(Reboot) Push Switch
  • MP1/MP7 controlled LED Indicators
  • LED Power Indicator
  • JST EH type Header Connectors for Optional XLR output driver board.

Technical Design Topics

The audio input circuit uses OPA1632 for high-quality fully-balanced differential input and ADC driver. Two ADCs are driven with inverted signals to eliminate their non-linear characteristics. As a result of this, Odd order harmonics were reduced drastically. Additionally, it decreases the noise floor by 3dB. Substructing two ADCs data in the digital domain accumulates the differential ADC performances. The output stage has GND shiftable (within the power supply voltage) circuitry called as "Differential RCA Outputs". This supports using multiple power amplifiers which have some different GND levels each. An optional balanced output board design is provided for XLR input provided amplifier users. A TDM-Interlink enables transmitting and receiving 8-Channel data between the boards. So you can feed Audio-data, POT position, DSP parameter, or GPIO status information to another board. Dual-mono construction enables higher stereo separation and double-sized DSP processing steps. So you can use 192kHz or 96KHz fs settings easily.

I hope you can enjoy high-quality embedded audio codecs on ADAU1701 as well.

CyberPit

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