advanced audio recording
dynamic wave table generation with Cyclone 4
  Cyclone IV


sample rates




96kHz 192kHz

Audio DSP

This module uses the classical wave table synthesis known from PPG instuments. In contrast to the original instrument, no statically stored waveforms are used here, but they are generated dynamically and continuously with a LaPlace waveform generator whose weightings can be set dynamically. It is an improoved version of my first Wave Table Module having more waves and a higher generation precision too.

This method allows the desired waveform to be generated and modified in real time and, in addition, these constant or changing waves can be walked through depending on the ADSR curve information or an LFO. Since the weighting factors can also be controlled dynamically, the sound can thus be changed simultaneously and in real time in 2 dimensions.

See a german article in the UCNET here: LaPlace Waveform Generation

 Hardware Unit
Altera Cyclone IV + ADC/DAC board

Altera DE-155 board für audio dsp workstation with 16384 voices

The Altera Cyclone 4 DE2-115 from Terasic is used to implement both the test system and the final wave table module running together with my sound synth. The additional card attached has both a stereo audio codec chip and high speed ADCs and DACs which are used for signal observation during development and monitoring signals at a physical oscilloscope. The analog audio is down sampled to 192 kHz for highest precision.

Wave Table Synthesis

In this version, 7 to 15 waves are used to create harmonics in order to build the desired music wave. Using several of these waves, a virtual wave table processing is possible by walking through these waves dynamically.

WAVE Table Synthesis with dynamic wave generation
Simple sine waves with harmonics changing their shape by 2D sound processing

WAVE Table Synthesis with dynamic wave generation
Complex Waves from sine waves changing their shape by 2D sound processing in real time

 In the current synth I am using both multiphase ADSR as well as static driven wave selection to control the wave. According to the virtual generation of the wave, there are no artifacts as known from the PPG style generation. The wave is totally continous at any point of time even when no blending in between the waves is performed.

Wave Designer

The old platform C3 is used to design the waves. It has full VGA output, cursor, mouse support and wave allocation function in order to dynamically select the waves. VGA via video 1280x1024 as well es TFT 800 x 600 is possible.

WAVE Table Synthesis with dynamic wave generation
wave designer showing the change of the wave over the time

click here to see the former version



© Dipl.-Ing. Jürgen Schuhmacher 2011