Audio Research is primarily known for its tube amplifiers, but the company also produces amplifiers with solid-state components. The new dual-mono power amplifiers S-100 and S-200 use solid-state components instead of tubes. The circuit topology is fully balanced and operates in Class AB. The S-200 is the most powerful of the new duo and stands out with its VU meters on the front.
The S-200 is tubeless. Audio Research uses bipolar transistors for its power amplifiers. This design reportedly offers exceptionally controlled and dynamic power delivery, which should be particularly noticeable with music containing fast transients. With 200 watts per channel into eight ohms, doubling to 400 watts into four ohms, the S-200 clearly positions itself in the high-performance segment. Crucial is not only the sheer power output, but also the ability to operate stably, even at low impedances.
Audio Research deliberately uses a classic Class AB topology for both the S-200 and the S-100. The goal is to combine the sonic coherence of a Class A circuit with the efficiency and performance of modern transistor amplifiers. The choice of bipolar transistors instead of MOSFET components is noteworthy. According to the designers, these are intended to enable exceptionally transparent and dynamically differentiated sound reproduction. For the listener, this translates into precise transient response, controlled bass, and clear reproduction of complex musical passages.
A damping factor of 300 in the 20 Hz to 1 kHz range emphasizes the emphasis on accurate bass reproduction. The specified frequency response extends from 20 Hz to 20 kHz within a narrow margin of ±0.1 dB. This speaks volumes about the linear operation of the S-200.
Visually, the S-200 aligns with the manufacturer's current design style. The aluminum chassis is available in a black or silver anodized finish. Notable features include the massive, integrated heatsinks on the sides and the VU meters recessed into the front panel.
The S-200 measures 48.26 x 17.78 x 44.45 centimeters (W x H x D) and weighs 19 kilograms. It consumes just 0.25 watts in standby mode, 48 watts in standby mode, and up to 475 watts under full load.
The smaller S-100 shares many of the S-200's features. Technically, the Audio Research S-100 is also based on a consistent dual-mono design. Each channel has its own power supply with a separate toroidal transformer. This minimizes crosstalk.
The power output is somewhat more modest compared to its bigger brother, the S-200, but it still delivers 100 watts per channel at eight ohms, and at four ohms, the power doubles to 200 watts. The fully symmetrical circuitry further reduces interference. Using the balanced inputs, the input sensitivity is 1.4 volts RMS at rated power and the input impedance is 100 kOhms.
The rated total harmonic distortion (THD) is less than 0.1 percent across the range from 0.25 watts to rated power into eight ohms. The frequency response is within ±0.1 dB between 20 Hz and 20 kHz. The S-100 also has no tubes or MOS-FETs, but only bipolar transistors.
The chassis is crafted from precision-milled aluminum, available in black or silver anodized finish. The massive, custom-machined cooling fins and the sleek front panel, devoid of visible screws, are particularly striking. It measures 48.26 x 17.78 x 44.45 centimeters (W x H x D), and it weighs 19 kilograms.
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