Anthem Electronics STR Power Amplifier

Anthem's STR power amplifier, the flagship of the series, is consistently designed for stability, control, and clean signal processing. It is aimed at users who want to combine high power reserves with a technically sophisticated architecture – without sonic coloration or unnecessary compromises.

High power reserves for demanding loads

With 400 watts per channel at 8 ohms, 600 watts at 4 ohms and up to 800 watts at 2 ohms (with all channels driven simultaneously), the STR power amplifier offers very high output power across a wide load range.

In practice, this performance capability primarily ensures stability: even with complex impedance curves or dynamically demanding program material, playback remains controlled and low in distortion. The high current delivery capability ensures that both quiet details and rapid level changes are reproduced cleanly.

Dual-mono design for clean channel separation

The internal design follows a true dual-mono principle. Two separately wound toroidal transformers supply the channels independently of each other. This separation reduces mutual interference and improves channel stability, especially at high output levels.

Together with a clearly structured signal path, this contributes to precise spatial imaging and stable stereo representation.

High-current output stage in Class AB technology

Sixteen bipolar output transistors are used per channel. This design is optimized for high current delivery and linear behavior. The Class AB topology combines good efficiency with low distortion in the practically relevant power range.

The advantage of this architecture becomes particularly apparent with low-impedance or phase-critical loudspeakers: The power amplifier remains load-stable and delivers consistently reproducible results.

Elaborately designed entrance stage

The input stage is based on a cascoded, complementary feedback structure. The goal of this circuit topology is to achieve the most linear amplification possible while simultaneously extending the frequency range and reducing noise.

Additionally, transistors in critical signal paths are selected and paired to minimize tolerances and increase signal integrity.

Non-invasive protection circuit

With integrated ALM™ (Advanced Load Monitoring) technology, the power amplifier continuously monitors operating parameters such as temperature, current, and voltage. Unlike conventional protection circuits, this system only intervenes when limits are reached.

In normal operation, the audio signal remains unaffected, while at the same time reliable protection against overload or malfunction is ensured.

Soft start and system integration

A sequence-controlled soft-start system limits the inrush current and protects both internal components and the power supply. Additionally, a combined trigger and signal detection system enables automatic switching on and off of the power amplifier.

This facilitates integration into existing systems, especially in combination with preamplifiers or home cinema setups.

workmanship and features

The housing is mechanically robust and designed for effective heat dissipation. An integrated 7-inch graphic display supports status indication and system control. High-quality, low-impedance speaker terminals ensure a secure and low-loss connection.

Combination with the STR preamplifier

In combination with the STR preamplifier, a technically coordinated system is achieved. The clean signal processing in the preamplifier and the stable power amplification of the power amplifier work together seamlessly, enabling consistent overall performance without bottlenecks in the signal chain.

TECHNICAL DATA

• THD (400W): 0.0007% (1kHz), 0.004% (20kHz)
• Signal-to-noise ratio (IEC-A, Ref. 400 W): 121 dB
• Frequency response (20 Hz – 20 kHz): ± 0.1 dB
• Power bandwidth (-3 dB at 400 W into 8 ohms): 91 kHz
• Slew rate: 30 V/µs
• Damping factor (20 Hz – 1 kHz): 360
• Channel separation: 101 dB (100 Hz), 98 dB (10 kHz)
• Input impedance: 10 kO (RCA), 15 kO (XLR)
• Input sensitivity (for 400 W at 8 Ω): 2.1 Vrms
• Voltage gain: 29 dB
• Intermodulation distortion (IMD, 300 W):
  • ITU-R (19kHz + 20kHz): 0.0006%
  • SMPTE (60Hz + 7kHz): 0.0016%
• Power requirements (120 V version): single-phase AC power source, 108 V – 132 V, 60 Hz
• Power requirements (220–240 V version): single-phase AC power source, 198 V – 264 V, 50 Hz
• Power consumption:
  • Standby: 310 mW
  • Idle: 65 W
  • Typical playback levels: 150 W – 300 W
  • High playback levels: 600 W – 1100 W
• Mass:
  • Height: 17.2 cm
  • Width: 43.2 cm
  • Depth (without power cord): 47 cm
• Weight (unpacked): 27.3 kg