Hammond T-500 TWG Digital Control & Signal Conditioning

Initial Project Outline

• Phase 1 - Testing Analog Devices AD7771 8-channel ADC with Teensy 4.1 Microcontroller
• Analysis of TWG (Tonewheel Generator) output signals
• Pre-ADC conditioning
• SPI control of ADC
• ADC signal output to Teensy via SPI
• Digital mixer on Teensy (note selection & amplitude control)
• Analog output from Teensy (mostly for fun)
• Matlab analysis of audio signals
• Determine feasibility of final mixing & stereo/mono effects on Teensy
• Phase 2 - Testing Alhambra II FPGA as Digital Signal Processor
• Determine multi-channel capacity of FPGA
• Basic DSP on FPGA (LP, BP & HP filters)
• Digital mixer on FPGA
• Advanced DSP on FPGA (effects, multiple filters, see DAFX book)
• Determine feasibility of final mixing & stereo/mono effects on FPGA
• Phase 3 - Design of 88-Channel ADC Board
• Likely to include 11 each 8-channel ADC chips
• 11 FPGAs? How many channels can one FPGA handle? 
• Phase 4 - MIDI control via Teensy
• Note-on messages
• Effects selection and control
• Phase 5 - Analog Output Section Design
• Selection of proper stereo DAC
• Design of separate DAC board
• Phase 6 - Power Supply Design
• Determine power requirements of individual components
• Design power supply (!)