The STK4231-II is a high-grade, thick-film hybrid integrated circuit (IC) from the STK series, specifically designed for high-fidelity (Hi-Fi) stereo power amplification. It belongs to a family of ICs that provide a dual-channel (stereo) output in a single, compact SIP-22 (Single In-line Package). This "Type II" version is optimized for low distortion and is a standard replacement component in high-end vintage receivers and home theater amplifiers.

Specifications

• Output Power: 100W+100W (Stereo) at THD=0.4%.
• Operating Voltage: Recommended ± 51V (Max ± 75V).
• Package Type: SIP-22 (22 pins).
• Load Impedance: 8Ω (Standard).
• Frequency Response: 20Hz to 20kHz.
• Maximum Junction Temperature: 150°C.
• Thermal Resistance: 1.1°C/W.

Features

• Thick-Film Hybrid Construction: The internal components are mounted on an insulated metal substrate, ensuring excellent heat dissipation and electrical stability.
• Integrated Muting Circuit: Includes a built-in stand-by and muting circuit to eliminate "pop" noise during power-up or power-down sequences.
• Low Distortion: Engineered for high-fidelity audio, maintaining clear sound quality even at high output volumes.
• Standardized Pinout: The STK4201 series shares compatible pinouts across different power ratings, simplifying design and replacement across various amplifier models.
• Constant Current Circuit: Utilizes a built-in constant current circuit to reduce supply voltage ripple and improve the signal-to-noise ratio.

Common Applications

• Hi-Fi Audio Amplifiers: Main power stage for home stereo systems.
• Active Subwoofers: Driving high-power low-frequency drivers.
• Professional Audio Equipment: Used in public address systems and studio monitoring amps.
• Repair & Restoration: Replacing failed amplifier modules in classic Sony, Technics, or Kenwood receivers.

Usage Tips

• Thermal Management: This IC generates significant heat at 100W output. It must be mounted to a large, properly rated aluminum heat sink with high-quality thermal grease before power is applied.
• Symmetric Power Supply: Ensure the power supply is a "split" or "dual" type (e.g. +51V,0V,−51V). Operating with an asymmetric supply will cause immediate failure or severe distortion.
• Short Circuit Protection: The IC does not have robust internal short-circuit protection. It is critical to use fuses or a protection circuit on the speaker outputs to prevent the IC from blowing if the speaker wires touch.
• Voltage Headroom: While the max voltage is ±75V, running it at the recommended ±51V is safer for longevity, especially with fluctuations in mains power.

Datasheet