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Old 8th January 2011, 07:21 PM   #11
SY is offline SY  United States
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Apparently Russians can't spell "bolt."
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Old 8th January 2011, 07:24 PM   #12
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Quote:
Originally Posted by DF96 View Post
One of the mysteries of the universe is why Americans measure gm in micro-mhos, but Europeans measure it in mA/V (=milli-mhos). 4400 micro-mhos = 4.4 mA/V.

Was the linear JJ 12AT7 the frame-grid version? I would expect a frame-grid to give greater linearity, if done properly, as it means the valve is basically planar as far as the electrons are concerned and this should lead to constant mu.
There is no mistery in the American measure of GM, 4400 micro-mhos is far more precise than 4,4 ma/v
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Old 8th January 2011, 07:32 PM   #13
Salas is offline Salas  Greece
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Quote:
Originally Posted by SY View Post
Apparently Russians can't spell "bolt."
''B'' is pronounced as ''V'', it is the Greek 'beta' letter. Greeks we pronounce it ''vita''. Russians got alphabet from two Byzantium era Greek monks from Salonica. One's name was Cyril. Hence they use Cyrillic. The Byzantine two headed eagle facing east and west is their emblem still, Moscow was symbolically the third Rome after the fall of Constantinople and Czar meant Caesar.
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Old 8th January 2011, 07:37 PM   #14
DF96 is offline DF96  England
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4400 and 4.4 both contain two significant figures, so possibly same precision, except 4400 is ambiguous as it could mean four sig figs so it actually conveys less information. GM make automobiles, gm measures valves.
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Old 8th January 2011, 07:39 PM   #15
SY is offline SY  United States
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4725 is four significant figures. But then again, our electricals weren't designed by Lucas.
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Old 8th January 2011, 07:59 PM   #16
DF96 is offline DF96  England
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If I wanted to be awkward (moi?) I could say that 4725 might be about 2.5 sig figs. 4729 would definitely be 4 sig figs. Anyway, this is getting well OT so one of the mods will be slapping our wrists soon. Wait a minute: SY is a mod, so that's all right then. Have we answered the OPs question?
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Old 8th January 2011, 09:36 PM   #17
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Is there a value that relates to 100% ( NOS ) ?
- Not when just looking at one ebay item which gives one figure.

Is there a value that relates to "don't buy it " - it's only got a few months left
- Not when just looking at one ebay item which gives one figure. But there is confidence that the valve works as it is expected.


Is there a value that relates to "used" but lots of life left?
- Not when just looking at one ebay item which gives one figure.

Valve testers in general do not provide comparable measurements with a high level of accuracy (as you may expect of other meters of different manufacturers). They weren't subject to an international certification scheme for accuracy, and they don't come with a golden sample that you can pass around and use as a comparison standard. As such, they tell you the valve is working based on valve tester expected range of values for a tube, and if you test many on the same tester over time then confidence builds that a particular valve is behaving in a normal manner. It gets complex when using them for more detailed assessments.

Ciao, Tim
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