Jeff, you make it sound so easy; some of these vintage Threshold amps seldom appear online.
I've had a S300 Series II, and now have a S350/e. Both run trouble free and I keep mine powered 24/7. The stasis/e series are indeed the last ones with Nelson Pass onboard.
It's interesting to me that the S300 is a clean, simple looking design whereas the S350/e is much more complicated looking internally. Also, the S350/e came with not only an operating manual like the S300's but an additional separate service manual packed with schematics. Maybe it escaped me with the S300, but with the S350/e even the top cover has a part number stamped into it. The later over-attention to parts accounting makes me wonder what was happening at the factory shortly before it changed hands.
Echoing Oldears comments, The T series amps used IGBP's (insulated gate bipolar transistors) which are no longer available. Aside from today's Texas factory, a good repair resource for vintage Thresholds is:
http://www.rsvlonline.net/vintageamp/
Check out the archive there for some idea which Threshold is right for you. For my money, the optical bias later Stasis series (uprated A/AB from AB, have black top covers and say optical bias, instead of overall feedback free, on the front panels) and the e series are the cream of the crop. However I'm sure any of the earlier products reflect the same build quality. Real class acts like Threshold seldom disappoint.
I've had a S300 Series II, and now have a S350/e. Both run trouble free and I keep mine powered 24/7. The stasis/e series are indeed the last ones with Nelson Pass onboard.
It's interesting to me that the S300 is a clean, simple looking design whereas the S350/e is much more complicated looking internally. Also, the S350/e came with not only an operating manual like the S300's but an additional separate service manual packed with schematics. Maybe it escaped me with the S300, but with the S350/e even the top cover has a part number stamped into it. The later over-attention to parts accounting makes me wonder what was happening at the factory shortly before it changed hands.
Echoing Oldears comments, The T series amps used IGBP's (insulated gate bipolar transistors) which are no longer available. Aside from today's Texas factory, a good repair resource for vintage Thresholds is:
http://www.rsvlonline.net/vintageamp/
Check out the archive there for some idea which Threshold is right for you. For my money, the optical bias later Stasis series (uprated A/AB from AB, have black top covers and say optical bias, instead of overall feedback free, on the front panels) and the e series are the cream of the crop. However I'm sure any of the earlier products reflect the same build quality. Real class acts like Threshold seldom disappoint.