Electro-Voice CPS-4
A 4-stage-fan, 1800-watt fixed-installation amp that EV built to survive brownouts, back-EMF, and the guy who patches the wrong thing at 2 a.m.
Overview
The CPS-4 sits at the top of Electro-Voice's CPS Series of power amplifiers. EV aimed the line squarely at the fixed-installation market rather than the touring rig. According to EV's own documentation, the series was developed with "the unique needs of the fixed-installation customer in mind," and the spec sheet backs that up. The CPS-4 is rated at 1800 watts maximum per channel into 2 ohms at 1 kHz with both channels driven. That drops to 1300 watts into 4 ohms and 850 watts into 8 ohms. Under the stricter rated-power condition (under 0.2% THD, 20 Hz to 20,000 Hz, both channels driven) it delivers 1500 watts into 2 ohms, 1200 into 4, and 750 into 8. Those are big numbers for a permanent-install box. The bridged rating is bigger still: 3600 watts into 4 ohms and 2600 into 8 at 1 kHz.
The protection architecture is what separates the CPS-4 from a generic high-power amp. EV built a 5-way protection and safety system into the series. It is designed to shield both the amplifier and the connected speakers from line shorts, thermal overload, power surges, signal degradation, and signal overload. The individual pieces are over-temperature protection, DC protection against direct shorts, an excessive Back-EMF monitor that guards against reverse current flowing back into the amplifier when a speaker fails, a low AC line voltage monitor to prevent problems during brownouts, and the cooling fan system. The CPS-4 gets the 4-stage front-to-rear fan arrangement. The smaller CPS-1 and CPS-2 make do with 3-stage fans. EV documents the cooling as quiet, which helps when the rack lives in a sanctuary or a conference room rather than a warehouse.
The other half of the story is dynamic range. EV's literature describes a "Nonlinear Signal Monitor," a dynamic limiter that caps amplifier distortion at under 1 percent, specifically to eliminate the hard-edged clipping that destroys speaker systems. Paired with a power supply designed for high peak delivery, it gives the amp a burst-signal output capability that EV claims exceeds 130% of the average continuous rating. The CPS-4 is built to handle the peaky transients of live voice and music without folding, which is the abuse a permanently installed system takes when nobody's minding the gain structure.
The spec sheet also lists a 40 V/μs slew rate, the highest in the CPS line, which climbs from 25 V/μs at the CPS-1 up through 30 and 35. Total harmonic distortion is under 0.05%, intermodulation distortion is under 0.01%, and crosstalk at 1 kHz is better than 80 dB. Input impedance on the balanced inputs is 20 k ohms. Power requirements are 120 V at 50-60 Hz, factory configured, so buyers should confirm the voltage configuration before dropping one into a rack. Protection also includes audio limiters, high-frequency protection, peak current limiters, inrush current limiters, and a turn-on delay. EV backed the series with a 3-year warranty.
The CPS-4 is not a "4-channel" amp, though people read it that way. The "4" in the model name is its position in the CPS hierarchy, CPS-1 through CPS-4, and it goes with the "4-stage" fan count. The CPS-4 is a two-channel amplifier, and the documentation states ratings with both channels driven.
Mix (August 2000, p.180) noted the CPS-4's Nonlinear Signal Monitor, which limits amplifier distortion to less than 1 percent.
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