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Threshold S/500 Series II Stereo Power amplifierThis is from when amps were made seriously. Amazing power, does everything well IMO.I have had this amp for 25 years or so and it has never had any issues. There is a thump when powering on, and some very light noise after it has been off for a few seconds. But as you can see the caps are not showing any visible issues, and the sound is great. You can though get kits to re-cap these or have the amp restored. I just have never felt the need-- I still use it all the time. Really only selling due to impending relocation.It is in really nice shape especially for it's age. A few scratches, some marks on the edges, not sure how that happened, and the original owner had the sharp corners of the heat sinks machined down. Not really noticeable (see pics), and probably is safer when you gotta move this thing.Local pick/sale only as it is too heavy to ship and it far outlasted the original box. Come take a listen if you can -- makes a great match with the Von Schweikert VR-4 speakers I am also selling.Any questions please let me know, and thanks for looking--
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Threshold Audio emerged in Sacramento, California, in 1974, founded by renowned audio engineer Nelson Pass alongside graphic designer René Besne and Joe Sammut. Pass, a pioneer in amplifier design, launched the brand with the groundbreaking Threshold 800A power amplifier in 1975, introducing a novel sliding bias system that boosted Class A efficiency while employing 48 output transistors in a sophisticated triple-series/triple-parallel configuration. This California-rooted heritage defined Threshold as an innovator during its original run, which spanned until the mid-1990s, after which the intellectual property changed hands, including a 1994 acquisition by investor Randy Patton, who integrated it with PS Audio and relocated operations to Camarillo.
The brand focused squarely on high-end amplification, producing iconic power amplifiers like the 400A and 800A, the Stasis series renowned for their balanced Class A performance, and preamplifiers such as the NS10, SL10, and FET range including the FET-1, FET-2, FET-9, and FET-10. Later designs, like the T-200 by engineer Michael Bladelius, continued this legacy. Threshold eschewed speakers, turntables, DACs, headphones, or cables, concentrating instead on pure analog amplification that prioritized sonic purity and robustness.
Threshold holds a revered position as a vintage high-end icon, cherished by collectors and audiophiles for its enduring sound quality and Pass's technical wizardry. Once a market leader in premium solid-state gear from 1975 to 1992, it remains a sought-after name in the used market, embodying boutique excellence rather than mass production, with modern revivals under Threshold Audio sustaining its elite reputation.
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