[sdiy] Xarp-56

Tom Wiltshire tom at electricdruid.net
Mon Nov 17 15:01:27 CET 2008


Well, you've done it again! Excellent work, congratulations.

How much control do you have over the model? I notice there seems to  
be a very long decay on the lower notes, which makes the sound quite  
"boomy" at the bottom, and not as "plinky" as I'd expect a harp to  
be. Presumably the actual _shape_ of decay curves and such like is a  
characteristic of the model, rather than something that is easily  
modified as a parameter. Is this correct?

I was also interested to see that you've tried decimation. How did  
you get on? What filter did you use? How did you derive it?
I'm particularly interested in this since I'm wondering about trying  
to do a 6 or 8-operator FM synth voice on these dsPIC chips I'm  
playing with, and running that at a higher internal sample rate would  
help with aliasing a lot (assuming I can squeeze the maths into the  
available time).

One day I'm going to have to stop messing about with general-purpose  
hardware and start designing some custom stuff with FPGAs, like  
you've managed to do. It's very inspiring stuff.


On 17 Nov 2008, at 04:32, Scott Gravenhorst wrote:

> Here is the Xarp-56 FPGA 56 voice physical model polysynth.
> http://home1.gte.net/res0658s/FPGA_synth/Xarp-56.html
> The sound clip is a piece of Tchaikovsky's "Dance of the Sugar Plum  
> Fairy" that I adapted for this instrument - the entire clip is  
> played on one Xarp-56 instrument.
> Verilog source is provided if you're interested.
> While you listen, remember that this it is a single integrated  
> circuit that is doing the DSP computations to make the sounds  
> you're hearing.
> Please enjoy...
> -- ScottG
> ______________________________________________________________________ 
> __
> -- Scott Gravenhorst
> -- FPGA MIDI Synthesizer Information: home1.gte.net/res0658s/ 
> FPGA_synth/
> -- FatMan: home1.gte.net/res0658s/fatman/
> -- NonFatMan: home1.gte.net/res0658s/electronics/
> -- When the going gets tough, the tough use the command line.
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