| a PLD-based modular electronic organ | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
This is a design of an electronic organ making use of DDS-based sound generation with programmable logical devices (PLDs). It is a modification of the smaller version, I created before, see PLD-ORGAN. It can now be configured for up to 6 octaves with the current oscillator design. The strategy is again to generate all required 12 fundamental frequencies with only one unit and then derive the sub harmonics by simple switching the digital vector. Compared to the former version, this concept was changed in that way, that octave switching can be done with simply mounting the cable in between the modules in a different way. Doing this the sound generation modules can be easily configured without reprogramming the PLD. They can also be stacked and overlaid for the same tone bank more than once to create overlay sounds. Also filtering has been improved. Next to the individual adjustment of the basic sound wave by distorting the R2R-ladder, a filter feedback is available for a more living sound. (not shown in the design). The final mixing is done by a 12ch-summation amplifier which also contains the switches for the keyboard.
The design has been done for Xilinx PLDs/FPGAs of the XC4000 type. They are relatively huge today (around 50 times larger than the 3020 type, I once started). A nice step would be to integrate my universal distortion sound module but unfortunately the PLDs do not offer enough calculation power yet. In the future, it might be possible to fully do this the digital way. |
 12 channel sound generation 6 frequency levels including 5 SUBs Digital 6 Bit Tone Generation Module R2R- Digital-to-Analog Conversion  frequency setup table Sound Recording For more information, see the former approach PLD-based Sound Generation for DIY organ |
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© 2003 Jürgen Schuhmacher