Zapco REF 150.6 — 6-Channel Class AB Reference Amplifier

Zapco REF 150.6 — 6-Channel Class AB Reference Amplifier

The REF 150.6 is a six-channel Class AB amplifier from Zapco's Reference series, rated 150 watts RMS per channel at 4 ohms, 220 watts per channel at 2 ohms, and 450 watts bridged into 4 ohms per bridged pair. THD is under 0.02% at 1kHz into 4 ohms at 70% rated power, with A-weighted signal-to-noise better than 102dB at full power and channel separation of 64dB — the highest in the Reference line.

Frequency response is 10Hz to 40kHz within ±3dB.

Six Channels for a Three-Way Active Stage

Six channels at reference measurements maps onto a three-way active front stage: tweeters, midrange, and midbass each with their own amplified channel pair.

Channel separation of 64dB matters more here than on a two- or four-channel. With six channels carrying six different filtered signals, crosstalk between them would blur exactly the separation an active system is built to achieve. Sixty-four decibels puts that well below audibility.

Six low-level input channels accept 0.5V to 8V with greater than 20K input impedance — enough range to take six discrete outputs from a processor without attenuation or matching.

Socket-Mounted Operational Amplifiers

Like the rest of the Reference series, the REF 150.6 carries MUSES8820 operational amplifiers on sockets rather than soldered, replaceable with the higher-specification MUSES02 or others without desoldering.

The factory parts are surface-mount devices on PCB adapters that fit the socket. Orientation is critical when fitting replacements, and Zapco recommends the work be done by a qualified technician.

System Application

A three-way active front stage from one chassis, or a full front-and-rear installation with a bridged pair driving bass.

At 2 ohms each channel produces 220 watts, and up to three pairs can be bridged at 450 watts each into 4 ohms, so channel count can be traded for power where the design calls for it.

Installation Considerations

Four ohms is the minimum load when bridging. Each channel sees half the load bridged.

The REF 150.6 operates from 9 to 16 volts with a 3 × 40A fuse rating — higher than the rest of the line — and measures 480 × 210 × 62 mm, the largest chassis in the series.

Add up the fuse values and size power and ground wire from that total and the run distance from the battery. Match ground gauge to power, keep the ground short, and secure it to clean bare metal on the frame. Six channels of Class AB needs airflow around the heatsink.

Specifications

• Configuration: 6-Channel, Class AB
• Power: 150W RMS × 6 @ 4Ω
• Power: 220W RMS × 6 @ 2Ω
• Power: 450W RMS × 3 bridged @ 4Ω
• THD (1kHz, 4Ω, 70% rated power): <0.02%
• Signal-to-noise (A-weighted, full power): >102dB
• Channel separation: 64dB
• Frequency response (±3dB): 10Hz–40kHz
• Low-level input channels: 6
• Input sensitivity: 0.5V–8V · Input impedance: >20K
• Working voltage: 9–16V · Fuse: 3 × 40A
• Dimensions: 480 × 210 × 62 mm
• Socket-mounted MUSES8820 op-amps, upgradeable

HF Audio Perspective

Six channels at reference measurements is a specific answer to a specific build: a three-way active front stage where every driver gets its own amplification and the amplifier is not meant to be the limiting element.

Consolidating that into one chassis simplifies the install — one power run, one ground, one location — at the cost of flexibility if the channel assignment later changes. The measurements are what justify it over a conventional six-channel: at this level the amplifier's own distortion and crosstalk are low enough that what you hear is the drivers, the processing, and the tune. Get those right and this amplifier will not be what holds the system back.