This is what it says at www.xintechs.com:
"Xin Technologies, Inc. (XTI) will not be accepting any new orders and is halting its commercial operations at this time. All previously processed and existing orders (as of July 7 2004) will be shipped. Technical support will be available through September 30, 2004, and can be reached via firstname.lastname@example.org
As of October 1, 2004, XTI will cease all operations.
The SuperDual manual is now available in PDF form. Click here to download the file.
XTI in its initial manufacturing of the SuperDual did find a design modification that improved the sound quality of the system. This became part of the SuperDual design and was implemented on all SuperDual amps shipped with the exception of those that were made before this change. Of course, the modification will be included in all pending amp shipments. If your serial number is less than 04061800 (not including 04061410, 04061412, 04061413, 04061705, 04061706) then your system needs to be updated. Please note that if your serial number is greater than 04061800 (or is not one of 04061410, or 04061412, or 04061413, or 04061705, or 04061706), then you already have the revision (and won't need to do anything). For those who need the upgrade, XTI will provide the upgrade free of charge if it is received before August 15, 2004. You need to send your system back to our address at this link at your own expense and risk. XTI will make the modification and will ship the updated system back to you at no additional charges to you."
Incidentally my SD has burst into life again so i may only have a glitch so i will use it all next week to check it is OK but will have to ship it back anyway for the revision. I wonder if the revision would mean the SD would need to be burnt in again ?