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Threshold S/300 Amp. This is a beast of an amp. Nothing compares. I've had them all. The S/300 hits where the S/500 cannot. It has slightly sweeter upper frequencies and a more nimble, airy, and intimate overall presentation. It's not power hungry and doesn't run hot Like the S/500. The S/300 can without question run perfect in an enclosed cabinet. I am the original owner. This unit comes with original Certificate of Ownership and flyer. I've black out name. See image. This is a legendary piece of high-end audio history: the Threshold S/300 Stasis Power Amplifier. Designed by the iconic Nelson Pass, this heavy-hitting, optical bias Class A/AB amplifier delivers a level of grip, transparency, and effortless musicality that modern amplifiers struggle to replicate at thrice the price.If you are reading this, you likely already know the reputation of the Stasis series. It features a unique, no-overall-feedback design where a pure Class A small-signal amplifier dictates the voltage, while a massive, high-current output stage provides the muscle without corrupting the signal. The result is a liquid-smooth midrange, sweet top end, and a bottom-end grip that can tame even the most demanding, low-impedance speaker loads. Specifications & FeaturesPower Output: 150 watts per channel into 8 ohms / 300 watts per channel into 4 ohmsDesign: Stasis linear state, optical bias Class A/AB, no overall negative feedbackPower Supply: Massive custom toroidal transformer with a heavy-duty capacitor bank for immense headroomForm Factor: Built like a tank with iconic oversized heat sinks and a thick brushed aluminum faceplate.ConditionCosmetic: Fantastic vintage condition. Doesn't look vintage at all. The faceplate is incredibly clean, and the heat sink fins are straight. The wear is light at best because audio is no joke in my home. Unit sat inside custom setup behind glass so hardly touched. Operational: 100% functional. Runs exactly as intended. Channels are perfectly balanced, the noise floor is incredibly low, and it delivers that signature effortless, holographic soundstage from the moment it warms up. But I guess this all depends on your setup. I only know how it sounded for me. Photos: I don't have good lighting. They aren't great. Grainy! I will see if I can take better pictures. ShippingThis amplifier is an absolute behemoth and weighs roughly 50+ lbs. It will be packed with extreme care, double walled box. Might take me a couple of days to pack. Shipping is exactly what UPS charges. No more. No less. No International shipments. Don't miss the chance to own a foundational piece of solid-state audio history. Feel free to message me with any questions!Not a store. No returns.
Generating expert take…
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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