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The Threshold SL-10 is a vintage, high-end direct-coupled Cascode/Class A preamplifier, made in the U.S.A. renowned for its extreme transparency, speed, and detail. It features a separate S/SL-1 power supply for improved isolation and uses advanced transistor-based gain circuitry without feedback with included XLR cable connector. It is a highly regarded preamp by audiophiles for its precision and build quality.This tandem is in Excellent condition, no blemishes or real signs of wear.Frequency response: 1Hz to 200kHzTotal harmonic distortion: 0.01%Gain: 33dB (MM), 20dB (line)Signal to noise ratio: 82dB (line)Output: 3V (Pre out), 12V (Pre out Max)Dimensions: 19" x 2.5" x 8"Service History: No service records were included from the prior owner. Here at the shop we did routine testing, cleaning and inspection.Cosmetic Condition: Overall we rated this at Very Good.In the Milwaukee Area? Stop in our shop to inspect/demoSee our feedback and thank you for considering. All the gear we sell is packaged with great care for safe arrival in the condition advertised.
Because this is an older, Nelson Pass-era preamp with an outboard supply, timing matters: survivors in clean, working shape are getting rarer, and this is the kind of vintage piece that’s often bought for the long haul. At US$1,075, the asking price looks fair to slightly favorable versus the small pool of recent used references I can find, with comparable listings around US$1,300–US$1,650 for nice examples, so this is not an ambitious ask.
The draw here is the sound: the SL-10 is well regarded for speed, transparency, and a very low-noise, direct-coupled Class A presentation, which makes it a strong fit if you want a revealing, classic solid-state preamp. Excellent condition is a real plus on a piece like this, and if the power supply is included and fully quiet, that adds meaningful value; I’d mainly want confirmation of full function and no service surprises, since age is the only real watch item on an otherwise compelling buy.
Independent perspective — not a price guarantee. Always verify condition, accessories and provenance before purchase.
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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