Sigma series amplifiers are designed to pack tremendous power, performance and value into relatively small and energy efficient chassis. The Sigma series AMP2 is derived directly from the acclaimed Delta series CA-D200, sharing both power supply and amplifier circuitry. In the same way that our CT series models use the same circuitry as the equivalent Delta series but in a different chassis1,
the AMP2 is actually the 200W/Ch CA-D200 in a Sigma series chassis. The AMP5 also shares these same power supply and amplifier topologies, but with the necessary changes implemented to accommodate its five-channel configuration.
The basis of the design is switching technologies, used
in both the power supply and audio stages. A Classé- 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 effort- lessly 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 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 distur- bance, the Sigma series amplifiers deliver their prodigious power while remaining effectively silent as far as the AC shared with preamp/processor and source components.
AMP2 and AMP5 audio circuits use a true digital archi- tecture, taking advantage of DSP to solve an issue called dead-band-time, the greatest source of distortion in oth- erwise well-designed class D amplifiers. Dead-band-time, somewhat analogous to 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.2 With inherently low distortion, the Sigma series amplifiers use only a small level of overall negative feedback, helping to achieve low intermodulation distor- tion. 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 perfor- mance.
The Sigma AMP2 and AMP5 owe their outstanding performance and value to the unique engineering and manufacturing capabilities of Classé in Montréal and the B&W Group globally. No other high-end audio designers have access to the resources necessary to deliver such amplifiers at such competitive prices. The AMP2 and AMP5 have been conceived and built as examples of quality and value without peer. They will stand as bench- marks in the advancement of class D amplifier technology.
10Hz – 20kHz, -1dB into 4Ω
200W rms into 8Ω All channels driven
400W rms into 4Ω Any two channels driven* 0.018% @ 1kHz All channels
driven to 1/8th power into 8Ω
116V peak to peak, 58V rms no load
116V peak to peak, 58V rms into 8Ω 100kΩ Balanced / 50kΩ SE
>80 dB below fundamental into 8Ω SE -100 dB at peak output into 8Ω (AES17) 200W @ 1/8th power into 8Ω
100V - 240V, 50/60Hz
Width: 17.00” (433mm)
Depth (excluding connectors): 14.57” (370mm) Height: 3.75” (95mm)
23.1 lb (10.48 kg)
30.0 lb (13.61 kg)
*each channel supports 400W output into 4 ohms but the AC Mains/power supply cannot support all channels driven simultaneously at this level, which would require over 2,500W and only occur under a special test condition. Every channel easily drives lower impedance loads.