advanced audio recording
Wavetable Module for the Music Synthesizer in VHDL
TABLE Module

1024 Samples RAM

16 Bit

VHDL Block Design
Signal flow in the PLD

Wavetable Module in VHDL for the digital audio workstation - Jürgen Schuhmacher

An optimized DDS module is used to equip the workstation with a precise wave table based sound generation. Using either DDS-based frequency generation or VA-modeled sine wave operation, a trigger sine wave is used to control the current phase of the sound signal.

According to the given frequency setting a multiple of it is used to generate the address for the SRAM in the FPGA leading to a precise phase relation of both the triggering wave and the generated wave thus eg 256, 512 or even 1024 dots per period can be accessed progressively. Any waveform can be loaded into the block ram so true wave table synthesis is performed. Phase jitter is eliminated by oversampling the wave with the FPGA clock frequency. For a 12 kHz wave, 4096 samples are used to generate the 4 samples for the 48kHz output using a CIC + FIR filter. Blockram is accessed my UART.

Real time S/PDIF sampling is planned.

Example Output
Signals from the PLD

Synthesized waves from wavetable module - scanned with VGA-Oscilloscope - Jürgen Schuhmacher
Example Waves on VGA Oscilloscope view

See also Reverb Module.

96 kHz
Audio DSP


© Sound of L.A. Music Productions 2006