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Phase Linear amps and Pink Floyd
PL nostalgic journey continues – let me drop a few lines spotted on the Internet on pro-sound applications of these fine amps and the link to Pink Floyd performance success.
It was evident by beginning of 70’ that the limits to design power amplifiers were just a bit over 150 watts per channel. So how to achieve higher sound levels?
High efficiency loudspeakers are always a good approach, but back then speaker power handling was not what you expect today. More power can be achieved with an electronic crossover (bi-, tri and quad-amplification) using separate power amplifiers for the low frequency loudspeakers (woofer) and the high frequency devices (tweeters and/or compression driver/horn assemblies). Also, with bi- and tri-amplification, you eliminate the passive high-level crossover network at the loudspeaker, which has some power loss. Plus, you had a separate amplifier for each loudspeaker, which is still not a bad idea.
At least all this was the case until Bob Carver came on the scene with his Phase Linear 700 power amplifier. Promising 700 watts, these units were relatively lightweight, had a relatively tiny power transformer, and minimal heat sinking. The Phase Linears sounded pretty good, with the sense of unlimited power, or at least a lot of peak power.
Instead of using transistors intended for audio, the Phase Linear had a load of video amplifier transistors that could take very high voltage. With the power transformer primary and secondary having close turns ratios, its purpose was more of line isolation then voltage/current transformation and so it could he very small, light, and inexpensive.
Companies like Audio Analysts, Heil Sound, and Clair Brothers Audio used Phase Linear amps back in the day for many years. That fact speaks volumes about the amps and how robust they are/were.
One of most famous PA systems was Clair’s S·4 that required one amp rack for each four-speaker cabinets. Each rack contained four stereo power units: Phase Linear 700-Bs, or SAE 2600s, depending upon how recently the rack was assembled. To reduce the damping factor caused by adding unwanted impedance to the amplifier by long speaker cables, Clair Brothers initially used to hang the amplifier racks with the speakers, but if an amp or speaker blew during a show there was no way to re-patch it until after the performance. Instead, it was decided to run heavier (12-gauge) cable, and keep the amplifiers on the ground in racks with four Phase Linears in each. The top amp in the rack drives the highs in four cabinets (two cabinets per side); the second amp down the mids in four cabinets; and the third and bottom amp the bass (one cabinet per side). The two top amps are loaded to about 350 watts into 8 ohms per side, while the bass amps are rated at about 700 watts into 4 ohms per side. All 700-Bs amps had transformer isolated from the console. The amp racks were placed on the sound wings in groups of four. Intake and exhaust fans on each rack were placed under a plywood enclosure that served as a cooling chamber. Large chunks of dry ice were set on a two-inch thick pad of styrofoam, and the chilled air contained within the plywood box allowed to recirculate through the amplifier racks, thus ensuring cooler operating temperatures – see the pictures. With more than 50 amp racks in use for the main speaker stacks, thousands of pounds of dry ice were required daily. The ice was delivered up to each tier by means of a makeshift elevator shaft built into the scaffolding: a chain-motor hoist was secured to a steel I-beam, and served as the motive force to raise and lower speaker cabinets, personnel ... and dry ice.
Pink Floyd was probably the most committed band to PL amps. It was common for Pink Floyd to modify off-the-shelf equipment for their own purposes, thereby creating unique products. Along with Crown and BGW, Phase Linear became one of the few brands of amplification taken seriously by the top touring bands of the early '70s. Whilst the Phase Linear 400 and 700 models were taken on board by the Floyd, because of their superior sound quality, in their regular domestic format they were unfit for the rigours of the road due to their slight physical construction and the weight of the transformers on their chassis. To compensate for this, the band's technicians designed a new metal chassis into which the amp would fit, while the mains transformer was removed from the amp and supported horizontally on the outside of the chassis. The band started using 700-Bs and then they swapped for so called Pink Floyd Mk III Power Amplifiers, that were nothing else than highly modified PL PRO700 (http://jerobison.blogspot.com/2008/0...irca-1979.html). The PL D-500 modified models powered Pink Floyd rehearsals before first public performance of “The Wallâ€.
Interesting links on Pink Floyd and their sound systems:
http://web.archive.org/web/200710281...eo/PFlive.html
http://www.brain-damage.co.uk/other-...source-un.html
PL nostalgic journey continues – let me drop a few lines spotted on the Internet on pro-sound applications of these fine amps and the link to Pink Floyd performance success.
It was evident by beginning of 70’ that the limits to design power amplifiers were just a bit over 150 watts per channel. So how to achieve higher sound levels?
High efficiency loudspeakers are always a good approach, but back then speaker power handling was not what you expect today. More power can be achieved with an electronic crossover (bi-, tri and quad-amplification) using separate power amplifiers for the low frequency loudspeakers (woofer) and the high frequency devices (tweeters and/or compression driver/horn assemblies). Also, with bi- and tri-amplification, you eliminate the passive high-level crossover network at the loudspeaker, which has some power loss. Plus, you had a separate amplifier for each loudspeaker, which is still not a bad idea.
At least all this was the case until Bob Carver came on the scene with his Phase Linear 700 power amplifier. Promising 700 watts, these units were relatively lightweight, had a relatively tiny power transformer, and minimal heat sinking. The Phase Linears sounded pretty good, with the sense of unlimited power, or at least a lot of peak power.
Instead of using transistors intended for audio, the Phase Linear had a load of video amplifier transistors that could take very high voltage. With the power transformer primary and secondary having close turns ratios, its purpose was more of line isolation then voltage/current transformation and so it could he very small, light, and inexpensive.
Companies like Audio Analysts, Heil Sound, and Clair Brothers Audio used Phase Linear amps back in the day for many years. That fact speaks volumes about the amps and how robust they are/were.
One of most famous PA systems was Clair’s S·4 that required one amp rack for each four-speaker cabinets. Each rack contained four stereo power units: Phase Linear 700-Bs, or SAE 2600s, depending upon how recently the rack was assembled. To reduce the damping factor caused by adding unwanted impedance to the amplifier by long speaker cables, Clair Brothers initially used to hang the amplifier racks with the speakers, but if an amp or speaker blew during a show there was no way to re-patch it until after the performance. Instead, it was decided to run heavier (12-gauge) cable, and keep the amplifiers on the ground in racks with four Phase Linears in each. The top amp in the rack drives the highs in four cabinets (two cabinets per side); the second amp down the mids in four cabinets; and the third and bottom amp the bass (one cabinet per side). The two top amps are loaded to about 350 watts into 8 ohms per side, while the bass amps are rated at about 700 watts into 4 ohms per side. All 700-Bs amps had transformer isolated from the console. The amp racks were placed on the sound wings in groups of four. Intake and exhaust fans on each rack were placed under a plywood enclosure that served as a cooling chamber. Large chunks of dry ice were set on a two-inch thick pad of styrofoam, and the chilled air contained within the plywood box allowed to recirculate through the amplifier racks, thus ensuring cooler operating temperatures – see the pictures. With more than 50 amp racks in use for the main speaker stacks, thousands of pounds of dry ice were required daily. The ice was delivered up to each tier by means of a makeshift elevator shaft built into the scaffolding: a chain-motor hoist was secured to a steel I-beam, and served as the motive force to raise and lower speaker cabinets, personnel ... and dry ice.
Pink Floyd was probably the most committed band to PL amps. It was common for Pink Floyd to modify off-the-shelf equipment for their own purposes, thereby creating unique products. Along with Crown and BGW, Phase Linear became one of the few brands of amplification taken seriously by the top touring bands of the early '70s. Whilst the Phase Linear 400 and 700 models were taken on board by the Floyd, because of their superior sound quality, in their regular domestic format they were unfit for the rigours of the road due to their slight physical construction and the weight of the transformers on their chassis. To compensate for this, the band's technicians designed a new metal chassis into which the amp would fit, while the mains transformer was removed from the amp and supported horizontally on the outside of the chassis. The band started using 700-Bs and then they swapped for so called Pink Floyd Mk III Power Amplifiers, that were nothing else than highly modified PL PRO700 (http://jerobison.blogspot.com/2008/0...irca-1979.html). The PL D-500 modified models powered Pink Floyd rehearsals before first public performance of “The Wallâ€.
Interesting links on Pink Floyd and their sound systems:
http://web.archive.org/web/200710281...eo/PFlive.html
http://www.brain-damage.co.uk/other-...source-un.html
