McIntosh amplifiers at Woodstock 1969

Gregory

Gregory

Soundco Kid
I've found and edited a photo of the MI-350 amplifiers that powered Woodstock in 1969, ten amps in all for a total of 3500 watts. The original photo below can be found by searching the web however its quality is very poor. It took between ten and twelve attempts to get a reasonably clear and presentable image.

MI350_x10_012.jpg



These amps were apparently mounted in cases set on a platform under the stage to keep them off the ground, which was wet due to weather during the festival. You can read about the MI-350 and see the schematic here: MC-3500.html


-Gregory
 
Gregory said:
Yep.. and here's a data sheet on the 6LQ6 Beam Pentode of which the MI-350 uses eight.. 6LQ6.pdf


-Gregory
Click to expand...



I wish I had the slightest comprehension of how any of this stuff worked (tube or ss). I only have a smidgen of understanding.

I am surprised, however, that GE let a data sheet leave their factory with a typo.

I wish I wasn't such a journalism major...
 
jchouston said:
I wish I had the slightest comprehension of how any of this stuff worked (tube or ss). I only have a smidgen of understanding.

I am surprised, however, that GE let a data sheet leave their factory with a typo.

I wish I wasn't such a journalism major...
Click to expand...

Do you mean perveance vs. perveyance?

Perveance has a specific vacuum tube technical meaning, see below.

http://www.google.com/search?aq=f&gcx=c&sourceid=chrome&ie=UTF-8&q=perveance

1. Perveance
Is a measure of the relationship between the beam current and voltage of an electron beam. It is defined as the ratio of the cathode current to the 3/2 power of the anode voltage. Due to the size of this unit the normal unit used is the microperv.
Found on http://www.albacom.co.uk/Web/Site/defenc

2. perveance
the quotient of (1) the mean convection current by (2) the three-halves power of the voltage that corresponds to the mean kinetic energy of the charge carriers within a stated cross-section of the beam or by (2) the three-halves power of the voltage of the accelerating electrode
Found on http://www.electropedia.org/iev/iev.nsf/

3. perveance
quotient of the mean convection current by the 3/2 power of the voltage that corresponds to the mean kinetic energy of the charge carriers within a stated cross-section of the beam or by the 3/2 power of the voltage of the accelerating electrode
Found on http://www.electropedia.org/iev/iev.nsf/

That's why we're not old vacuum tube electrical engineers.
 
Since these were built 80 miles away in Binghamton NY worst case they could copter in replacement parts - like a replacement glass face or something :music:.
 
c_dk said:
You missed swervice and greid...
Click to expand...

Yeah, swrvice and gried, missed 'em too! But since he mentioned just one, I thought it was that. Boy, the typewriters, type setters, and proofreaders all missed those.

On topic, interesting tube though, and a very unusual application. Seems that maybe we've not been striving for more power enough through tubes.

What was interesting to me on reading the links was the Stereo Review comment that said in the review, the amps run cool with a cooling fan??? Is that cool relative to any amp pushing that many tubes, or do they really run relatively cool?
 
w1jim said:
Since these were built 80 miles away in Binghamton NY worst case they could copter in replacement parts - like a replacement glass face or something :music:.
Click to expand...

I thought the GE tube plant was in Owensboro, KY. I interviewed there for a job with the company that took over the factory building. The Sylvania plant was in Altoona, PA (close?).
 
mech986 said:
Yeah, swrvice and gried, missed 'em too! But since he mentioned just one, I thought it was that. Boy, the typewriters, type setters, and proofreaders all missed those.

On topic, interesting tube though, and a very unusual application. Seems that maybe we've not been striving for more power enough through tubes.

What was interesting to me on reading the links was the Stereo Review comment that said in the review, the amps run cool with a cooling fan??? Is that cool relative to any amp pushing that many tubes, or do they really run relatively cool?
Click to expand...

Mcintosh was not perfect either if you read some of their black and yellow brochures.
 
Good reason to keep those amps off the ground and dry...ZZZZZZZZZZZZZZZZZZZZZT!

Great photos!
 
jlovda said:
I thought the GE tube plant was in Owensboro, KY. I interviewed there for a job with the company that took over the factory building. The Sylvania plant was in Altoona, PA (close?).
Click to expand...
Yeah, but the McIntosh factory was in Binghamton - if they needed some unique parts. Bet they had some extra tubes at the concert site - if they hadn't all been converted to bongs.
BTW, drove by the Woodstock site a few weeks ago (now known as 'Bethel Woods'). Hit a deer a mile from there - which resulted in an inordinate amount of damage to my car, but more to the deer.
 
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