Classé Expands Sigma Series With New 350W Mono Amplifier Classé has expanded its Sigma series to include a new monaural amplifier, the Sigma MONO, which is rated at 350W into 8 ohms and 700W into 4 ohms.RS Staff ⋅ Sep 28, 2015 Classé has expanded its Sigma series to include a new monaural amplifier, the Sigma MONO, which is rated at 350W into 8 ohms and 700W into 4 ohms, and built on the company’s proprietary Sigma amplifier design. “In the short time they’ve been available, our proprietary Sigma series amplifier designs have been showered with praise from numerous audio critics and consumers worldwide,” said Dave Nauber, president at Classé. “The Sigma MONO builds on this innovative platform, pushing the performance to heights that surprised even us—and we’re pretty hard to surprise! “The pure, effortless sound that is the hallmark of the Sigma MONO derives from an unlikely source: a massive switch mode power supply,” Nauber added. “Critical portions of the amplifier’s circuitry surpass what is available in the two- and five-channel Sigma models. A new analog input stage, modifications to the operation of the output stage, and new output filters are employed to optimize the performance of this high-powered monaural amplifier.” A pass-through feature allows the input signal to be forwarded to a second amplifier for bi-amplifying or to drive a subwoofer amplifier. This allows the amplifiers to be located closer to each speaker; a single, long interconnect can be used to connect the preamp to the first amp, followed by a short interconnect to the second Sigma MONO, or even a third and a fourth amp.