Classé Launches Sigma MONO 350W Amplifier

Legendary audiophile electronics manufacturer, Classé, has just announced a new addition to their Sigma series: the new Sigma MONO 350W power amplifier.  As its name implies, the new Sigma MONO is a monoblock power amplifier conservatively rated at 350W into 8 ohms and 700W into 4 ohms.  Classé says that the new amplifier delivers all the benefits of Classé’s proprietary Sigma amplifier designs in an even higher performance package.

The new monoblock amplifier is the latest addition to the Sigma series, which Classé launched earlier this year.  Until the launch of the MONO, the Sigma series consisted of the universally acclaimed 7.1 channel SSP-800 preamp-processor and two amplifiers: the two-channel AMP2 (200W x 2) and the five-channel AMP5 (200W x 5). Like their siblings, the MONO shares the same external form-factor and low-profile footprint.

Stacked, Dual Sigma MONO amplifiers.  The footprint of the new amps is identical to their siblings'.

Classé says that 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. Classé says that when combined together, all these changes put the Sigma MONO amplifier’s performance a clear step ahead of the AMP2 and AMP5 and make it a true reference amplifier design

Speaking of design, Classé says that the Sigma MONO's audio circuits use a true digital architecture. They take advantage of DSP to solve an issue called dead-band-time, which Classé says is the greatest source of distortion in otherwise well-designed class D amplifiers. Dead-band-time is similar to switching distortion in a class A/B amplifier. It is the time when the plus and minus halves of the amplifier are both off. In an ideal design, it should be as close to zero as possible and in Classé's implementation, the dead-band-time is less than three nanoseconds.

According to Classé, 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.

Top view of the new Sigma MONO.  The slightly pinkish rectangles help dissipate heat from the amp and into the chassis for even cooler-running performance.

The Sigma series has been designed to try and bring a lower price point to Classé products, allowing a broader base of individuals to consider Classé. Additionally, the Sigma series has also been specially designed to cater to the custom installation market with some truly ingenious industrial design features and a slim form-factor that's perfect for rack mounting or component stacking.

Speaking of special features for the installer or audio aficionado, a special pass-thru 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.

Rear view of the Sigma MONO.  A special pass-thru feature allows the input signal to be forwarded to a second amplifier for bi-amping or to drive a sub.

Like the the AMP2 and AMP5, the MONO is a switching design that is Classé's own design.  In fact, Classé's switching design is one of the very, very few that has garnered universal praise from reviewers and completely challenged the notion that switching design amplifiers cannot sound equal or superior to Class AB designs.

Dave Nauber, President of Classé noted, "The pure, effortless sound that is the hallmark of the Sigma MONO derives from an unlikely source: a massive switch mode power supply. 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.”

The new Sigma MONO retails for $4,000 each or $8,000 for a stereo pair and will be available to dealers in October.

I've had the pleasure of auditioning the Sigma Series and I can tell you that the sound is simply beautiful.  If you have the monetary means, and have been waiting for a high performance, highly efficient amplifier that can deliver some serious output, then the new Sigma MONO deserves your attention and audition.