[music-dsp] Open Source DSP Analog Simulation Synth

Eric Brombaugh ebrombaugh1 at cox.net
Wed May 13 12:06:55 EDT 2009

robert bristow-johnson wrote:

>> The general idea is to marry a low to mid-range FPGA to a reasonably powerful 
>> embedded processor with plenty of I/O. The ARM processor provides USB, SD, 
>> MIDI and user-interface functions, while the FPGA implements the synthesis 
>> algorithms. I've only begun to explore the possibilities with this - a simple 
>> MIDI monosynth which only uses less than 20% of the FPGA resources.
> but what if you want dozens of voices simultaneously?

The present design is just a step along the way. For polyphony I'll be 
extending the FPGA logic to handle many simultaneous voices - I'm 
estimating that I can get several hundred oscillators running at once. 
The hardware can support a variety of synthesis techniques simply by 
loading different FPGA bitstreams from the SD card memory.

> i know of at least one company that had been exploring this for multi-voice sample playback (the FPGA is doing all of the sinc-like interpolation effort).  then they're gonna couple the sample-playback output into their existing chips for processing and effects which is really dumb.  they had (and it isn't me) one insightful engineer who suggested also doing whatever necessary processing on individual voices on the same FPGA, but they didn't listen to him either.

Just using the FPGA for sinc interpolation seems short sighted, but I 
imagine they're thinking along the lines of "we've already got the 
hardware/software synthesis problem nailed with our existing solution". 
Not very forward-looking, but probably cheaper and quicker to market.


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