Zapco ST-4B Amp 4 Channel Class AB Full Range Bridgeable Amplifier 4x 65w RMS

The Zapco ST-4B is a 4-channel Class AB full range bridgeable amplifier rated at 4 x 65W RMS at 4 ohms and 4 x 90W at 2 ohms. It accepts both RCA and OEM speaker level inputs, making it suitable for use with factory or aftermarket head units. It is part of Zapco's ST-B amplifier range.

This listing is the ST-4B. The ST-B range is also available as the 5-channel ST-5B, which adds a dedicated subwoofer channel.

Key specifications

• Model: ST-4B
• Channels: 4, full range, Class AB
• Power @ 4 ohms: 4 x 65W RMS
• Power @ 2 ohms: 4 x 90W
• Bridged @ 4 ohms: 2 x 180W
• Inputs: RCA and OEM speaker level
• Input sensitivity: 0.25V to 5V
• Crossover: variable full / LP / HP
• THD @ rated power: < 0.2%
• Signal to noise ratio: > 90dB
• Channel separation: > 45dB
• Frequency response: 15Hz – 30kHz ±1dB
• Net dimensions: 182(W) x 52(H) x 280(L) mm
• Overall dimensions: 182(W) x 52(H) x 310(L) mm

ST-4B 4-Channel Class AB Amplifier

Stable into a 4 ohm bridged or 2 ohm stereo load. Suits speaker upgrades on both factory and aftermarket systems.

• MOSFET power supply
• RCA and OEM speaker level input
• Variable input gain control
• Variable full / LP / HP electronic crossover
• Variable bass boost
• Power @ 4Ω: 4 x 65 watts
• Power @ 2Ω: 4 x 90 watts
• Power @ 4Ω bridged: 2 x 180 watts
• THD @ rated power < 0.2%
• Signal to noise ratio > 90dB
• Channel separation > 45dB
• Frequency response: 15Hz to 30kHz ±1dB
• Input sensitivity: 0.25V to 5V
• Net dimensions (mm): 182(W) x 52(H) x 280(L)
• Overall dimensions (mm): 182(W) x 52(H) x 310(L)