http://www.audioheritage.org/vbulletin/showthread.php?605-JBL-SA600-integrated-amplifier
https://www.hifiengine.com/manual_library/jbl/sa600.shtml
http://audiokarma.org/forums/index.php?threads/jbl-sa-600.182877/
https://www.manualslib.com/manual/924555/Jbl-Sa600.html
https://arstechnica.com/civis/viewtopic.php?f=6&t=660963