6550-6550A-6550B-6550C - What are exactly Differences ??

[tiefbassuebertr]

Sound differences by tubes of same type from different manufacturers are good known and not to find by compare of the individual data sheets.
But the same is to observe by the various suffixes of the 6550.
Who knows the exactly differences and the mean of "A", "B" and "C" (6550C comes only from Svetlana as I know) ?

 

[Zero Cool]

My understanding is that the B and B2's were not very stable tubes. the C's are much better.

 

[WildOne]

OK,

What about the ones that I have that say?

6550R
Or the ones that say?

6550/WE

Not sure what they stand for?

Thanks
WO