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Old 19th Aug 2019, 5:05 pm   #1
Valvepower
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Default Woodstock PA system....

Hello,

With all the features about the 50th anniversary of Woodstock I wondered what sort of PA they used.

With a bit of trawling the net I found a few articles:
http://fohonline.com/articles/milest...0-years-after/
https://hometheaterreview.com/how-mc...red-woodstock/
https://www.mcintoshlabs.com/brand/n...odstock-Sound2

The bottom line it was all powered by 20 McIntosh MC3500 350-watt valve amplifiers, although there are couple of lone DC300 in sea of valve amplifiers in one of the pictures, although I couldn’t find reference to it in the articles. Maybe they were used as monitor amplifiers? Also, the they were still new, and their reliability would have been a concern, whereas the McIntosh’s would have been more reliable.

Ps. I did find a thread on The Gear Page site, but I didn't include this link as I felt it wasn't correct "link" etiquette

Terry

Last edited by Valvepower; 19th Aug 2019 at 5:33 pm. Reason: Add McIntosh Link
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Old 19th Aug 2019, 5:21 pm   #2
paulsherwin
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Default Re: Woodstock PA system....

I suspect you're right, and the transistor amps are driving the foldback monitors. It must all be documented somewhere.
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Old 19th Aug 2019, 5:56 pm   #3
G6Tanuki
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Default Re: Woodstock PA system....

Fascinating that the McIntosh amps used a set of push-pull-parallel 6LQ6 TV "sweep tubes" rather than a couple of big 813-style ones.

Was this perhaps cheaper? Or possibly a nod towards reliability - with four tubes in each half of the push-pull setup you could lose one tube and things would continue (with a bit more distortion) until the end of the set.

(lots of parallel tubes also mean you can trade lower HT volts against higher HT current - 500V at an amp or so is more open-air-rainy-venue-friendly than 2KV at 250mA)
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Old 19th Aug 2019, 6:31 pm   #4
Valvepower
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Default Re: Woodstock PA system....

Hello,

Just been thinking in terms of time scales and Woodstock being 50 years ago and looking back to 1970 makes the Crown DC300 vintage equipment, much as if you were to look back 50 years from 1970, you’d be looking at early crystal sets and two valve receivers (RR page 65-68) and the birth of broadcasting from 2MT

The DC300 soon found its way to driving the main FOH speakers.

Regards using 6LQ6 I think G6Tanuki is right on all counts of cost, reliability and lower HT. EAR use the PL509 in their EAR 509 100watt amplifier.

Terry
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Old 19th Aug 2019, 8:10 pm   #5
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Default Re: Woodstock PA system....

Quote:
Originally Posted by G6Tanuki View Post
(lots of parallel tubes also mean you can trade lower HT volts against higher HT current - 500V at an amp or so is more open-air-rainy-venue-friendly than 2KV at 250mA)
And with the lower HT you need a lower ratio in the output transformer and this militates towards better bandwidth and less disturbance from strays.

David (once the constructor of a 4x813 audio amp)
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