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Classe Sigma Series Monaural Amplifier-Black-Sigma MONO

Model #: Sigma MONO
At a Glance

Classe Sigma Series Monaural Amplifier-Black with switch mode power supply and power factor correction circuit

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The Sigma MONO is the reference design for the proprietary Class amplifier platform introduced in the Delta series CA-D200 and Sigma AMP2 and AMP5 models. With completely separate chassis for each channel, the monaural amplifier architecture eliminates the possibility of crosstalk between channels and allows speaker cable lengths to be held to a minimum to minimize losses. It efficiently delivers a prodigious 350W into 8 and 700W into 4, suitable for the most difficult speaker loads and critical listening applications.

The basis of the design is advanced switching technologies, used in both the power supply and audio stages. A Classe- designed Switch Mode Power Supply (SMPS) and Power Factor Correction (PFC) circuit, each operating at over 90% efficiency, provides a crystal-clear reservoir of over 1kW of power. The low frequency dynamics, extension and control of these amplifiers and their ability to effortlessly drive difficult speaker loads can be credited in large part to the powerful and sophisticated power supply they employ. This combination of SMPS with PFC allows the Sigma series amplifiers to draw current from the wall throughout the entire voltage cycle, avoiding the sharp spikes of current drawn by conventional power supplies. Such sharp and short current demands cause high-frequency harmonics on the AC mains. By creating no such disturbance, the Sigma series amplifiers deliver their prodigious power while remaining effectively silent as far as the AC shared with preamp/processor and source components.

Sigma MONO audio circuits use a true digital architecture, taking advantage of DSP to solve an issue called deadband-time, the greatest source of distortion in otherwise well-designed class D amplifiers. Dead-band time, like switching distortion in a class A/B amplifier, is the time when the plus and minus halves of the amplifier are both off; it should be as close to zero as possible and in this design, it is less than three nanoseconds.1 With inherently low distortion, the Sigma series amplifiers use only a small level of overall negative feedback, helping to achieve low intermodulation distortion. Proprietary driver stage FETs ensure quick and precise switching of the output stage, contributing to the amplifiers’ vanishingly low dead-band-time and maximizing their efficiency. The critical output stage filters are then used to filter only the 384-kHz switching frequency, leaving the amplifier with a neutral, extended and open upper midrange and high-frequency performance.

The Sigma MONO includes a special pass-thru feature, enabling the input signal to be fed through an output, in either balanced or single-ended form, to drive a second amplifier for bi-amping or to a powered subwoofer. The advantage is that only a single interconnect from the preamp/processor is required and additional amplifiers may be daisy-chained using short interconnects.

Compared with the Sigma AMP2 and AMP5, the Sigma MONO utilizes even higher performance analog input circuitry, incorporates changes to the DSP to optimize performance for its higher output power, and includes upgrades to passive components in the power supply and output filters. Combined, these changes put the Sigma MONO amplifier’s performance a clear step ahead of the remarkable achievement introduced in the AMP2 and AMP5, making it a true reference amplifier design.

Useful Documents


Power On Consumption (watts):130
Power Off Consumption (watts):0.5
Signal to Noise Ratio:109 dB

Misc. Specs

Depth (in.)14.57
Height (in.)3.75
Width (in.)17
Product Weight22.0000
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