early Marshalls and 6550s mystery

Talk about the evolution of Marshall's.

early Marshalls and 6550s mystery

Postby dai h. » Sat Apr 04, 2009 7:19 pm

forgive me if this has already been addressed before somewhere(I do remember various discussions about Jimi and 6550s but not this point specifically).

According to various sources (Michael Doyle's History of Marshall, Pittman's Tube Amp Book, Ritchie Fliegler's Amps!), the story with 6550s (seemingly always the GE version is the one that shows up AFAIK) is that Marshall's distributor wanted a more reliable tube (than the EL34) then henceforth US (and Japanese also IIRC) market Marshalls came with 6550s in lieu of EL34. The earliest date given (out of the above sources) is "(a)round 1972"(Fliegler). What seems odd to me is that the factory "Mark II" version schematics clearly denoting 6550s are all marked "JULY 70". As far as I know, the GE6550 was introduced in 1971 or '72. So does this mean that 6550s showed up stock even earlier than '72(Doyle gives a date of '74), and that the version used was the Tung-Sol(since the TS seems the only version extant at the time in 1970--the GE arriving shortly after and the Sylvania a little after that)? I suppose I should look through my chassis pics.
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Re: early Marshalls and 6550s mystery

Postby 908ssp » Fri Apr 10, 2009 5:54 pm

Do they show revision dates on those schematics? Alterations or maybe be done later than the original date of the print .
Alex

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Re: early Marshalls and 6550s mystery

Postby dai h. » Sat Apr 11, 2009 9:45 am

hey thanks alex, I think the factory schematics in question all had "JULY 70" plus a date (D/M/Y) which were mostly(? IIRC) different on each of the schematics. I'll need to take another look and see if there is something I missed, didn't notice, etc.
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Re: early Marshalls and 6550s mystery

Postby Hamilton » Sat Apr 11, 2009 7:47 pm

The earliest I've seen is '74, and those were hit and miss.
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