via this auction
"Here's the chance you've been waiting for. For sale is an incredibly rare Arp 2600 synthesizer with the Tonus logo. What makes this Arp special over most of the ones you see is it has the superior sought after 4017 oscillators, said to be more stable than the later versions and also with a fatter analog tone. It also has the rare Moog Filter which Arp was later sued over [not true - threatened but not sued] and had to change the design [true]. 
The later design is said to be weaker and thinner sounding. This Moog filter is super creamy and buttery, very incredible sound. The synth is 100% fully functional, recently tuned/calibrated and gone over, all sliders are clean and jacks are working and power supply board has been recapped. The keyboard keys all trigger properly, and has an upgraded connector jack that isn't as flimsy as the original connectors. Also upgraded is the power cable, it takes standard 3 prong instead of the proprietary oval shape. The only issue is 3 slider shafts are broken off, the slider still work but the shafts are shorter without the knob caps (which could be glued back on or replace the sliders entirely if desired). Cosmetically, the synth face looks very nice, crisp graphics and not much wear. The outside of the synth does show quite a bit of wear, especially on the lid covers. The lids for both keyboard and main unit are included but show a bit of peeling, so be sure to check out the pictures and make sure you like it. The cosmetics could easily be touched up with a retolexing if desired or you can appreciate the vintage character to it. The sound is the important part which is just really incredible and noticeably better than the other G-clef or black/orange 2600s I've played that didn't have the 4017 and Moog filters in them. I am open to offers but remember while your offer is pending someone else may snap this up. Don't miss out on this gem!"
