Audio Research S-100 Power Amplifier Review – Beyond Just Tubes

Explore how Audio Research’s S-100 power amplifier blends transistor technology with musical finesse for top-tier stereo systems.

Introducing Audio Research’s Transistor Powerhouse

When you think of Audio Research, tube amplifiers usually come to mind—those warm, glowing beasts that have defined audiophile listening rooms for decades. But the American company is proving they’re not a one-trick pony by expanding their transistor lineup with the new Audio Research S-100 stereo power amplifier. This latest entrant embraces classic solid-state design—specifically a Class A/B output stage built on bipolar transistors—while staying true to the brand’s musical soul.

Crafted with a dual-mono architecture, the S-100 features two toroidal transformers and fully balanced circuitry. It pumps out a robust 100 watts per channel into an 8-ohm load, doubling to 200 watts at 4 ohms. This is a powerhouse designed for demanding stereo systems that crave a blend of tight control, dynamic punch, and crystal-clear transparency.

Audio Research’s Signature Musical Transparency in Solid-State Form

Audio Research is famous for tuning every amplifier to prioritize musical expression and sonic clarity—and the S-100 is no exception. This unit is their compact yet ambitious foray into modern solid-state territory, meticulously engineered and manufactured in their Minnesota factory alongside their revered tube models.

The goal? To deliver transistor amplification that doesn’t sacrifice the nuanced musicality Audio Research is known for. It’s the kind of amplifier that respects the music’s soul, letting every note breathe and every instrument sing with precision.

Dual-Mono Design: Keeping Channels Pure and Power Stable

At the heart of the S-100’s design is the “dual-mono” principle—each stereo channel has its own dedicated power supply, complete with a separate toroidal transformer. Why does this matter? It dramatically cuts down on crosstalk and interference between channels and ensures stable, consistent power delivery, even when the music demands sudden surges.

The rated output is 100 watts per channel into 8 ohms, but it doubles to a hefty 200 watts per channel at 4 ohms. This means the amplifier handles low-impedance and complex speaker loads with ease, delivering ample current that’s critical for keeping demanding loudspeakers under tight control.

The fully balanced circuitry further reduces noise and distortion. When fed via balanced inputs, the S-100 boasts a sensitivity of 1.4 V RMS to reach full output and sports an input impedance of 100 kOhms—making it a versatile match for high-end preamplifiers.

Bipolar Transistors: A Choice for Clarity and Dynamics

Unlike many transistor amplifiers that lean on MOSFETs, the S-100 uses bipolar transistors in its output stage. This choice is deliberate, aiming to achieve superior transparency and dynamic nuance. What does this mean for your listening experience?

You get razor-sharp transient response, tightly controlled bass, and a clean, detailed rendering of complex musical passages that truly reveals the recording’s depth.

In terms of technical specs, the amplifier’s total harmonic distortion is impressively low—under 0.1% from a modest 0.25 watts up to full rated power at 8 ohms. Frequency response is practically flat, within ±0.1 dB across the full audible spectrum of 20 Hz to 20 kHz. These numbers confirm a very linear and faithful amplification performance.

Design and Build: Elegance Meets Functionality

Visually, the S-100 embodies Audio Research’s classic aesthetic but with a fresher, cleaner twist. Its chassis is machined from solid aluminum and available in either black or silver anodized finishes—both exude a refined, modern vibe.

The amplifier’s hefty heat sinks are custom-designed for efficient cooling, quietly managing the considerable power inside. The front panel is sleek and minimalistic, with no visible screws interrupting the clean lines. Its dimensions (19” wide, 7” tall, and 17.5” deep) make it a natural fit for traditional Hi-Fi racks, while the substantial 42-pound weight speaks to its robust mechanical construction.

In standby mode, the S-100 draws a mere 0.25 watts, with idle power consumption around 48 watts. When driven hard, it can consume up to 475 watts—reflecting the combination of high power reserves with reasonable baseline efficiency. Its gain level is set at 26 dB, and it features a low output noise floor of less than 60 microvolts, making it well-suited for use with high-resolution speakers where even the slightest background noise can be distracting.

Availability and Pricing

The Audio Research S-100 is already available for purchase. In Europe, it carries a recommended retail price of $12,300 USD, regardless of the finish chosen. This pricing positions the S-100 firmly in the premium segment, reflecting its sophisticated engineering and high-quality build.

Wrapping Up

The Audio Research S-100 is a standout example of how transistor amplifiers can deliver not just raw power but musical artistry. By combining classic dual-mono design, bipolar transistor output stages, and a commitment to sonic transparency, this amplifier challenges the notion that tubes have a monopoly on musical warmth and nuance. Whether you’re driving complex speakers or seeking a refined solid-state partner for your high-end preamp, the S-100 is a compelling contender.

“This amplifier lets every note breathe and every instrument sing with precision.”
— from the review

FAQ

• What is the power output of the Audio Research S-100?
  It delivers 100 watts per channel at 8 ohms and doubles to 200 watts per channel at 4 ohms.
• What type of transistors does the S-100 use?
  It uses bipolar transistors in the output stage for enhanced transparency and dynamic response.
• How does the dual-mono design benefit the amplifier?
  Dual-mono architecture uses separate power supplies for each channel, reducing crosstalk and improving power stability.
• What are the dimensions and weight of the amplifier?
  The unit measures 19” (48.26 cm) wide, 7” (17.78 cm) tall, 17.5” (44.45 cm) deep, and weighs approximately 42 pounds (19 kg).
• Is the Audio Research S-100 suitable for high-resolution speakers?
  Yes, with its low noise floor and high power output, it pairs excellently with high-res speaker systems that require a quiet background.

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Valeriy Bagrintsev Founder & Chief Content Creator

Valeriy is the founder of Just Plugged and a tech reviewer focused on consumer electronics, software, and buying guides. He brings years of hands-on experience researching and evaluating tech products to help readers choose better technology with confidence.

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