Phase Linear and Pink Floyd

laatsch55

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#1
Phase Linear amps and Pink Floyd
[HR][/HR]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
 

fitz43

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#4
Phase Linear amps and Pink Floyd
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 Wall”.

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
I wonder where you'd find a schematic for the "highly modified PL PRO700".....
 

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#7
I don't know if the Pro700 was very different than the Claire Bros 700. Claire had a set of component selections that they wanted in the 700 Pros they bought. IIRC a few of them werre; 2SD555's as outputs, for the Zoebel network insterad of the 2-3watt 10 ohm resistors they spec'd 1-5 ohm dale chassis mount 50 watt. There was a lot of this going on all the time. PL actually built some special; high frequency amps in the 700 model for Bell Labs. Ed has related a lot of this type info. He's the de-facto PL historian. In fact I just got off the phone with him and got to talk to a former Phase Linear technician who did the final functionality tests, Named Warren. We have had a couple questions answered tonight. They did not assemble the amps all in one place with one person responsible for the entire assembly. The borads would be populated by a certain group, the chassis would have the transformers and outputs mounted, THEN THE GIRLS got em. The girls would wire the entitre amp awire thge boards in, and do final assembly. The average could do -----------2 a day....
 
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#8
Wow. Very Interesting. Pink Floyd and PL. I guess thats Like the Grateful Dead and McIntosh. I like Pink Floyd much better. Lol
 

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The original output transistors weren't for video. The DTS-411's were developed for automotive CD ignition systems. Ed has told me the story about how the RCA guy and Bob crossed paths but it escapes me right now.
 

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laatsch55

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#13
The Phase Linear 400 and 700 amps used by the Floyd since the early
'70s were re-racked at the end of 1974 by Bill Kelsey and Peter Watts,
who had replaced the Phase Linear front panels with new engraved signs
which read "Pink Floyd Power Amp". In preparation for the "In The
Flesh" tour, the band purchased the new and more powerful Phase Linear
Dual 500s, and Nigel Taylor supervised their custom racking inside a
Brit Row-built 19-inch cube-shaped chassis. Each chassis, which
housed two amplifiers, was designed to enable simple disconnection of
wiring for servicing on a workbench.
 

P.L.F.

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#14
Hello,
I am so happy to see this thread :)... Already added some info to the similar one here: http://www.audiokarma.org/forums/showthread.php?t=484964

Maybe two more remarks found on the Internet:

- Phase Linear was building 350 watt per channel amplifiers back in the 70's. The next biggest amplifier at that time was the Crown DC300 at 150 watts per channel. Pink Floyd's Dark Side of the Moon tour in the 70's used a multi-channel sound reinforcement system power by Carver's Phase Linear amplifiers (remember we had quad 33 1/3 vinyl surround in them days). The Carver design was quite radical at the time, unfortunately they also had a propensity to set themselves on fire if not effectively cooled (dry ice cubes…). Carver designs would use higher voltage capacitors in the power supply. The higher the voltage the less capacitance available for a given size. A high current design (for the sake of comparison) will have lower voltage caps with higher capacitance available. The high current design will keep a constant voltage longer under heavy load because of the increased storage capacitance. The Carver design starts with a higher voltage less capacitance; the voltage drops or swings under heavy load. The trick is to not drop the voltage or sag to the point of clipping. The high current design with more storage capacitance will typically push current at a constant voltage longer with less voltage sag. The Carver design deals with the peak demand with voltage swing.

- Many quite large concerts (such as Woodstock in 1969) used remarkably little power. The Woodstock system is said to have used 10 x McIntosh MI-350 mono valve amps - a total of 3,500W. There is some disagreement on this, and surprisingly little real information. Many of the early (even quite large) systems only used about 1500W in total, and this was generally far more than could be obtained economically from any valve amps that were available at the time. Relatively large transistor amps became common in the late 60s (the Crown DC300/DC300A was rated at 150W into 8 ohms, but gave closer to 200W). These were only possible after various semiconductor manufacturers had perfected power transistors that were capable of handling significant voltage and current. It wasn't until around 1970 that these new devices became available at prices that mere mortals could afford, but once their price came down to something tolerable, things changed forever. Before this, the only (cheap) readily available high power transistor was the venerable 2N3055. In the early 70s, I built guitar amps and (mainly column) PA systems, and the only high-power transistor I could get at the time was the Solitron 97SE113 - now long gone, but not forgotten. The release of the Crown DC300 power amp in 1967 (closely followed by the DC300A, Phase Linear 200, 400 & 700 and a few others) signalled a new opportunity - plentiful power.

source(s):
http://www.watersish.com/archives/2011/09/phase-linear-700.html
http://www.proaudioland.com/roger-waters-pink-floyd.html
http://pfco.neptunepinkfloyd.co.uk/band/interviews/art-rev/art-sos2.html
http://www.colinbaldwin.com/docs/30yrs_of_Live_Production.pdf
http://sound.westhost.com/articles/pa.htm
 

laatsch55

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#15
I forgot to m,enmtion the links and original text of the first post was postaed by P'L.F. on AK and thought it was interesting enough to post! Thanks P.L.F.!!
 

P.L.F.

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#16
Thank you Lee! That's very kind of you.
And what's really amazing, no that many HiFi gears were used as PA amplifiers. Phase Linear, Crown, SAE, Quad? Some people say that it proved they were not actually HiFi. Then it's maybe right to ask how many recording studios used PL....? (Too) Simple answer is: a lot! I'd attach some pictures but for some reason using Safari on MacOS it's rather mission impossible on Phoenix Forum... :)
 

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#17
You're welcome Przem, just giving credit where credit is due. I read that whole 5 part article on Pink Floyds touring gear. Had no idea they took that much with em. 232,000 watts of amps----DUDE!! That's a lot.
As far as the PL's sound, let your ears be your guide. After the White Oak treatment and some DC protect, they have entered the no fault zone.
I'll ask Jer (jbeckva) The IT guy and one of the owners if he can do something about that.
 

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You're welcome Przem, just giving credit where credit is due. I read that whole 5 part article on Pink Floyds touring gear. Had no idea they took that much with em. 232,000 watts of amps----DUDE!! That's a lot.
As far as the PL's sound, let your ears be your guide. After the White Oak treatment and some DC protect, they have entered the no fault zone.
I'll ask Jer (jbeckva) The IT guy and one of the owners if he can do something about that.
Ok, here we go.. lessee here. Mac - check.. Safari - check... uploadum image?

geezer.jpg

Check (well, at least for me?)... hmmm...

PM me there Przem, so we can figure out your uploading issues...
 
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