I’m missing the sound of my super 6, but I also recently listened to a kyra and it sounded great too and gave me the same vibe. I wonder if what I like is just the sound of FPGA based synths.
So what all my choices for FPGA hardware synths? I know of the UDO Super 6, Waldorf Kyra, Novation Peak, and Novation Summit. Any I am missing?
Roland System-X?
There’s a DIY FPGA based synth called the Tiny Synth. There are a couple of related web-sites to look at for more information.
You can listen to audio at these sites. I quite like the sound.
I don’t think there is a FPGA sound per se, other than it being digital. You can treat an FPGA system very much like a software based system, excepting that when done correctly an FPGA is capable of more heavily calculation based processes, at less cost. This may also be part of the sound, the ability to do very compute intensive tasks. I won’t go into detail but FPGAs are programmed with code, that resembles normal software, but instead creates an electronic system that is specifically made to do the processing, as opposed to a program that is made to run on a general purpose processor.
There is also an FPAA which is an analog version of the same. I am not aware of any synth that uses these but it would be possible. FPAA Wikipedia
Another thing to consider is that smaller FPGAs could be used for smaller parts of a synthesis system, for instance as a filter, or something like Fourier transforms, etc. I am not aware of systems that use this but likely many synths use programmable logic, as a part of a more usual digital system. Also to consider are all the ASIC based synth systems, done on a lot of the older digital synths particular to synths done by Yamaha, Casio, etc. Again i will skip detail on this.
ADDED : It is also very possible to create using an FPGA, a general purpose processors, or portions of a general purpose processor, and then run software on that FPGA. This might be useful to create a general purpose processor, using existing created systems, and adding very specific synth specific process to those.
ADDED : Although we don’t know details of the specifics, but the ASM Hydrasynths has specialized custom hardware systems, that Medeli / ASM created and run with there own custom assembly language. These were likely developed as FPGA, and then converted to ASICs.
Schlappi’s Three Body Problem uses an FPGA in a eurorack oscillator.
I think there was a lot of skepticism about that decision, which I read as background for this video:
Not being a tech person, I found it interesting, since I didn’t know a lot about FPGAs or why they would be chosen over another type of digital synthesis chipset. But he’s pretty thorough in pointing out advantages and disadvantages of the decision.
The limited amount of use has been for more modern sounding synths but that’s just what they’ve been used for.
There’s nothing inherently special about using a FPGA, Software, ASIC, or DSP. Just different ways to achieve the same outcome with their own respective pros and cons.
Intellijel’s Shapeshifter is also an FPGA-based module. Does some bonkers stuff:
That was debatable with the Exodus Valkyrie. 
That was something more of the sound design though, something that Waldorf worked to improve.
Also given that larger FPGAs, large enough to apply to this size of problem, are relatively modern things as well.
Doesn’t the Peak/Summit use FPGA’s for its Oxford Oscillators?
Yes.
Cheers!