FPGA synth?

[Bigdutch]

Hi

I have an Arty (35T) board purchased in 2016 which I now have the time to look at. I looked up some online tutorials and was recommended to download 2015.2 Vivado for this particular board. I still had my original voucher based license (now superseded by the WebPack license which I ended up using anyway as the synthesise procedure failed - probably due to a hardware mismatch when I originally installed Vivado to a different PC). Anyway I shall probably install the latest Vivado and use that in future. 

I have been following with interest the trend for the Synth industry (the musical type!) to use FPGA (Kyra, UDO etc). Would the Arty board be good enough for this sort of direction or would I be better off with a Nexys Video (or even a Genesys) that both have an onboard audio codec and a bit more power. I have also looked for PMOD Midi boards without much luck. Things like NCO, DDS, PWM, Fourier Addition and all the filter types seems the sort of thing I could really get excited about but there are not many examples surprisingly.

If anyone has any experience in this area it would be great to have a few pointers about the choice of board and any shields or extras I should be aware of.

Cheers

 

 

[Bigdutch]

I have found the XFM project which looks good!

[xc6lx45]

Hi,

an FPGA can be a crazy powerful computing platform for audio but the water in the pool is very deep. If you stick to the shallow end, you're wasting 99.5 % of the potential performance. This only as something to look out for, shouldn't discourage you.

The main problem is, audio sample rates are, say, 200 kHz (you will need some oversampling) while the Artix FPGA is happiest beyond 200 MHz. There is a limited number of multipliers, and direct use at audio frequencies will quickly hit the resource wall.

If it gets serious, you'll do algorithm prototyping in C (or whatever) anyway, and it may come as a disappointment that even e.g. a Raspberry Pi turns out to be more powerful than the FPGA target... until you start pipelining / folding your data path. For example, I've gotten 18 000 000 000 multiplications 18x18 bit per second out of an Artix 35 T (yes, it does get a little warm...). This would be challenging on a PC CPU, less so on a graphics card.

But maybe (opinion) think the trend actually goes away from FPGA to DSPs. For example, check the Axe Fx forum on tube amp modeling details - there isn't just one algorithm and configuration but many different algorithms. This is much easier on a DSP than on an FPGA. Still, one of the biggest challenges in FPGA land is to come up with a meaningful problem ? and audio is not the worst place to start with. Especially if you like fixed-point math (hint: DSP48 has asymmetric multipliers - try a 25 bit data path and use the 18 bit side for coefficients etc).

For simple data paths (e.g. mixing console) an FPGA might even have the lead but I didn't do any cost analysis or the like.

 

 

 

[xc6lx45]

BTW if you search a little, I posted a nasty little 1-bit DAC that should be good enough for audio experiments a while back. You can do MIDI experiments with a UART at 31 kBit with a few external resistors