Crown PS-400

Two hundred sixty watts into four ohms, a kilowatt transformer, and a manual that tells you how to fix it - the Power Line Four was built to be worked, not admired.

Overview

Crown's PS-400 - sold in some markets as the Power Line Four, and appearing in listings as the Crown PS-400-PL4 - is a professional stereo power amplifier from Crown International, Inc. of Elkhart, Indiana. The factory service manual carries the document number K80078-7 and a date of 5/90, but that is the manual's revision date, not a production range. No confirmed production years have surfaced. One period review, Modern Recording (April 1982, p.66), listed the amplifier at $1,149 with a 19-by-7-by-11-inch chassis weighing 55 pounds. That review is also the only source for the price and dimensions, so those figures rest on a single citation.

The headline numbers are 260 watts per channel into 4 ohms in stereo, or 520 watts bridged into an 8-ohm load in mono. Crown's own trade advertising in Mix-Magazine (March 1983, p.69) made the same claim, and the same copy ran in Modern-Recording (July 1982, p.35) and DB-Magazine (April 1983, p.7) - a coordinated campaign across the pro-audio press. The bridged figure is the useful one for installed sound. 520 watts into a single 8-ohm load is enough to drive a distributed 70-volt system through the optional output transformer, or to push a difficult monitor in a control room.

What separates the PS-400 from the average pro amp of its era is the documentation. A full service manual exists, with disassembly procedures, test equipment lists, checkout routines, troubleshooting and a soldering refresher. The schematic and parts lists are still circulating. Most amplifiers of this vintage are a closed book when they fail. The PS-400 comes with a repair path.

The record is thin in other places. No production quantity is documented, no country of manufacture, and no common failure modes beyond a single repair-shop entry describing a unit whose only symptom was that the power came on.

Key Features

260 Watts per Channel, 520 Bridged

Crown rated the PS-400 at 260 watts per channel into 4 ohms in stereo, doubling to 520 watts into 8 ohms when bridged to mono. The 4-ohm stereo rating and the 8-ohm bridged rating are the same load on the output stage. Bridged mode simply uses both channels to drive one load, which is why the numbers line up. For a club system or a studio monitor chain, the practical setup is one PS-400 per cabinet, bridged.

MULTI-MODE Output Circuit

The PS-400 introduced Crown's MULTI-MODE output topology, described in the company's own advertising as a "three-deep design that eliminates audible distortion." That is marketing copy, not an independent measurement. The underlying claim is that the output stage was restructured rather than merely uprated. The surviving documentation does not settle whether MULTI-MODE delivered, and no independent distortion measurement for the PS-400 has been located.

IOC Input-Output Comparator

Crown's IOC circuit - input-output comparator - monitors the amplifier's own behavior and flags problems during operation: excessive input signal, incorrect load impedance, or a fault inside the amplifier itself. The front panel carries a pair of red LEDs for IOC action, green signal-presence indicators and an amber power lamp. It is diagnostic instrumentation built in rather than bolted on, so you find out something is wrong before the speaker does.

Plug-In Modular Options

The PS-400 was designed around field-installable modules. A balanced input module was available in active or passive form. A 70-volt output transformer could be added for distributed speaker systems. Dual cooling fans were an option for rack installations where convection alone would not keep the amplifier within thermal limits. All of these were described as installable without soldering. A separate XLR input adapter, the Crown PS-MOD/X, exists specifically for the PS-400 and PS-200.

Power Supply and Protection

The amplifier uses a 1-kilowatt transformer with computer-grade filter capacitors storing over 48 joules of energy, feeding two regulated supplies for isolation and stability. It accepts 50-400 Hz AC with selectable taps for 100, 120, 200, 220, and 240 volts, which is why the same chassis turned up in studios and touring racks on both sides of the Atlantic. Idle draw is 40 watts or less. At 330 watts total output it pulls 560 watts. It is short, mismatch, and open-circuit proof, with instantaneous limiting and no thumps or flyback pulses. A low-frequency interrupt puts the amplifier into standby if it sees DC above 10 volts or low-frequency output above 10 volts at 2 Hz, sampling every four seconds. Turn-on is delayed four seconds to suppress transients, and DC output offset is held to 10 millivolts or less, internally adjustable to zero.

Chassis and Thermal Design

Construction is all aluminum, with massive black-anodized heat sinks thermally joined to the chassis so the entire amplifier acts as a heat sink. That is why the optional fans exist. In a rack with poor ventilation, the chassis-only approach has limits. The front panel provides independent input level controls and a pushbutton power switch. The rear carries a stereo/mono slide switch, ¼-inch phone jacks and a three-terminal barrier block for input, color-coded dual binding posts on ¾-inch centers plus a 4-terminal barrier block for output, a ¼-inch stereo phone jack for output monitoring, and a ground-selectivity terminal block with a removable shorting strap. An 11-pin octal accessory socket accepts the balanced input modules or user options.

Historical Context

The PS-400 arrived when Crown was already the reference name in American professional amplification. In the company's own words, the amplifier was positioned for users who needed one chassis to cover multiple duty cycles, from club touring to permanent installation. The trade advertising that ran across Mix-Magazine, Modern-Recording, and DB-Magazine in 1982 and 1983 consistently paired it with the PS-200, and a period XLR adapter listing groups the two models together. No hierarchy between the two is documented. They were two amplifiers sold side by side, not a range with a top and bottom.

The service manual survives, the schematic survives, and the parts lists survive. What does not survive is any account of how many were built, when production started or ended, or what the "one review" beyond the Modern Recording citation actually concluded. The Archive has found no independent measurement of the PS-400's distortion, frequency response, or signal-to-noise, and no named competitors in the period press.

Collectibility & Value

Current asking prices on the used market sit in the $450 to $850 range, based on two listings. One is a plain "Crown PS-400 Amplifier" at $450, the other a working "Vintage Crown Amcron PS-400 2 Channel Amplifier" at $846. Neither listing carries a date, so those figures are a snapshot rather than a trend. A forum reference to the PS-400 as a "$200 amp" reflects a different market moment and a different condition, and should not be read as a current valuation.

For a buyer who actually intends to use one, the documentation is the draw. The full service manual is downloadable, the schematic circulates, and at least one repair-shop case is on record - a unit whose only reported symptom was that the power came on and nothing else happened. That is a symptom, not a diagnosis, and no common failure mode is documented. Crown's own manual notes that some components which appear standard are in fact special, and that structural items, covers, and panels are available from Crown only. Cosmetic parts are likely the hard ones to find, while the electrical side is well supported by the surviving documentation.

Units described as factory refurbished have appeared in listings. Owners who have compared the PS-400 to higher-rated amplifiers have been known to prefer its sound, though that is one enthusiast's opinion in a forum thread and not a measured result.