Owned all three versions
I can't remember how I first heard of this technology, but I think I started out by drooling over groove tube guitar amps, saving to buy one...(sadly, no longer in production before I could afford it), then seeing the SFX Spacestation (former designation) on the groove tube website. I bought a Mark I (again old designation) and was stunned by the surround effect. When Mark II came out, I was again saving, and groove tubes closed it's doors. For a long time I searched eBay, Craig's list, etc. hoping to find a Mark II, and although not so occasionally a Mark I would emerge, never a Mark II. Eventually I remembered the company owner's name (Aspen Pittman), so after an exhaustive research, I stumbled upon an obscure website named Aspen and associates which had absolutely no reference to groove tubes or space station SFX whatsoever. There was a phone number however, and upon calling, a gravelly, gruff voice answered which I knew to be Aspen Pittman from watching old YouTube NAMM videos. He explained to me why he had closed down his companies, and had no intention of starting back up. But upon learning of my exhaustive search for a Mark II,and that I was an aficionado of his amp technology,I was stunned when he offered to sell me one of the six remaining Mark IIs he had on hand to demo in case a large company came along and wanted to start producing them again. I immediately bought one and greatly enjoyed finally owning one and noticed a big improvement over the sound and loudness of the original. I stayed in touch with Aspen, and a couple of years later he informed me that he decided he was going to produce a new and improved model of the Spacestation. A year later, after it came out, of course I bought one and it truly is a dramatic improvement over the earlier models. I use it with guitar and keyboards to great effect.For guitar, I use it with an Axe-fx in combination with an Eventide rack processor. I am constantly being blown away by the mind numbing combinations that I have experimented with, and how good they sound through the ssv3. If there is a spacestation v4, I will be first in line to get one. After quite an extended history with this technology, I am still blown away by how good this technology sounds with stereo imagery. By the way, the 60 Hz hum another reviewer complained about will go away completely with an Ebtech Humx.