RADAR is a price search engine. We link to the original listing — we never sell direct. Transactions happen on the source site.
New, this was a serious high-power design rather than a budget amp, but at US$395 the used asking price is fair-to-firm, not a bargain. Your listing data puts comparable asks at a US$230 median, with the upper quartile reaching US$562, so this sits comfortably within the market but well above typical examples. A comparable dealer listing was also around US$399, while another used example was listed near US$264, reinforcing that condition and service history matter.
The ST-202 remains appealing for its muscular 150 watts per channel into 8 ohms, 200 watts into 4 ohms, high current delivery, and unusually open, natural MOSFET presentation. It is a strong match for demanding conventional speakers and can sound more refined than its age suggests. At US$395, buy only if the unit is demonstrably tested, quiet, and clean; confirmation that both channels, protection circuitry, and binding posts behave properly would make the price defensible.
Independent perspective — not a price guarantee. Always verify condition, accessories and provenance before purchase.
Quantum Science Audio (QSA) emerged in early 2020 under the leadership of Steven Tsang, an electronic engineering expert with deep roots in audio consulting. Based in Scottsdale, Arizona, with ties to Hong Kong where Tsang honed his expertise, the brand quickly carved a niche through relentless innovation in power components. Drawing from over two decades of proprietary research, QSA embodies a fusion of technical discipline and audio obsession, prioritizing subtle yet profound system enhancements.
The company's focus centers on high-performance aftermarket fuses, including thermal, slow-blow, automotive, and specialized AC variants like inlets, outlets, and panel breakers. QSA also extends into power receptacles and related accessories, all engineered to eliminate so-called "bottlenecks" in signal paths. Their lineup spans accessible entry points at around $28 to ultra-premium models commanding exorbitant prices, reflecting escalating tiers of advanced materials and quantum-inspired treatments.
In the hi-fi market, QSA occupies a polarizing boutique position among high-end enthusiasts, celebrated by some for transformative sound improvements in power delivery. Top models attract audiophiles chasing marginal gains, though skeptics dismiss the claims as overreach amid long production lead times. This niche status suits discerning buyers open to experimental upgrades in an otherwise crowded field.
See all Quantum Science Audio listings on RADAR.
