Features  
Year Made 1987
Original List Price $3095
Polyphony 16
Mulitimberal 8
Tones & Patches 32 Patches 64 tones
Type of Synthesis Digital Sampler (12 bit 15 or 30 Khz)
Maximum Sample Time 28.8 s @ 30khz
Effects none
Sequencer or Arpeggio none
Drum Sets none
MIDI programmable 1-16 for 8 samples
Outputs 8 asignable mono outs
Backup 3½" discs 
Options Digital Tablet, Remote Control, Director S

 
My Comments
I have started to get set up for my original shows and some cover ones and realised (for the original shows) I would need a decent sampler. I had been eyeing s-550 for about a year on ebay and think I got a decent deal on this one. However, I am very glad I got the manual, it is still very slow going figuring out how to set this thing up. Huge thanks to S group because I had no utilities disk and the new OS seems to work better. This one seems to be equipped with a SCSI port. I really wish I had a mouse for this but I was told to get one from Roland would cost about $100!! It would make editing alot easier. I got the Director S OS as well but haven't even tried to do anything with it yet, I think it will take a long time to master this unit. I will start to build a library of disks as I have time. 

Update Dec 2005 : I am starting to get frustrated. I believe you have to be an Idiot Savant to program this thing. Of course a manual for the proper OS would be cool. My manual is for 1.0 and still can't make samples.

Update Feb 2014 : it has been almost 10 years collecting dust before I was determined to figure out how to make this machine work. I finally think I understand how the architecture works and have made 2 disks to work with my Bėker show. Does this change the way I feel about this machine? Only marginally. There is a lot of time to make up for. May 2014 : As I try to fix some of the sampled vocals I find there is no normalizer or gain control in the editor. That would have been nice.
 
I rate it 
I bought it for 250$ c
I owned it from Apr 2004 - present
Current PrePay value 161$ us
condition of my keyboard
cosmeticaly There are a few scratches on the front.
electronically The unit seems fine
Status
2016: Still set up in rack 1

2014: finally started using it. I am using it for sampled vocals.

2012: set up and in the rack, but I hardly ever turn it on.

2010: set up with the other keyboards in the basement.

2008: I at the moment have it set up in my dining room! But this unit is also powered down. I haven't found the time to figure this thing out, but I think a mouse would really help. Maybe.

2006:I still hate this unit. The only manual you can get from Roland is the OS1.1 and the OS I have is CD5! Even so using the old OS I can't seem to tie a sample to a timber or tone or whatever. So the only samples I have are ones I got with the machine and a few ones I got off an auction. I guess I need space and time to play with this. So for now it is packed up.

 
Resources

Sgroup- users group dedicated to s series samplers, they have lots of samples tips and docs here. A great site and resource. Unfortunately no manual just links to places you can buy one.