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Old 22nd February 2004, 04:05 PM   #1
Jeffy74 is offline Jeffy74  Canada
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Default Plate color and getter

Hi!

I would like to know why some tubes are sold as "black plate" or "gray plate"? Here I have a lot of 6u8. Some look black and other look gray. I even have one with a black side and a gray side... Is it important to make a difference between color for quality or sounding?

And for getter... "D" "O" or cup getter... Is it important too?

thank you!
Jean-Francois
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Old 22nd February 2004, 06:54 PM   #2
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No. The characteristics are minimally different (if they were any bit significant, it'd be a different type number!). Especially in 6SN and SL7, you see a great variation in styles but they all tested the same.

I imagine the differences are very slight, leaving most of the "sound" to psychoacoustics (if you truely believe something is good, what's to stop your brain from making it sound good?).

Tim
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Old 23rd February 2004, 12:01 AM   #3
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Hi,

Quote:
Here I have a lot of 6u8. Some look black and other look gray. I even have one with a black side and a gray side... Is it important to make a difference between color for quality or sounding?
The 6U8/ECF82 is a triode + a penthode in the same envelope, I've never seen one with different plate materials for either of the elements under the same hood but, hey, it's not impossible.

As for the sound, the dark coloured ones are often preferred in audio circles as they have a different, more pleasing harmonic spectrum.

Whether that's important to you is entirely up to you to decide.
Since you hold a variety of different ones, you can do your own tube rolling and see what suits you best.

As for getters, well, I never pushed it as far as that but I know of others who come up with theories that may, or may not be based on actual fact.
As I don't know enough about it I won't forward any personal opinion on it, other than that getters are of the utmost importance to the life a tube.

What shape,size or materials are optimal, I think will depend on the type of tube and what's important to the manufacturer, I suppose.

Some of these issues have been, or perhaps still are, discussed on Audio Asylum....Me, I just gave up following up on that topic.

Cheers,
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Old 23rd February 2004, 12:27 PM   #4
EC8010 is offline EC8010  United Kingdom
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Default If the cup fits, wear it.

It could be that with some valves, those with a different shape of getter sound better than others. Tha fallacy is in ascribing the effect to the getter, when it is far more likely that that particular production run of valves was different within the anode structure.

Alternatively, you could just decide that it's marketing hype.
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Old 23rd February 2004, 12:39 PM   #5
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Hi,

Quote:
when it is far more likely that that particular production run of valves was different [B]within[\B] the anode structure.
Measurements have shown the black plate tubes to have almost immeasurable 4th and 6th harmonic distortion.

From tube rolling experience many of my audio buddies and myself often preferred the black plate tubes for preamp service.

These are often older NOS types, a good example is the excellent sounding (but by now unobtainable) GEC A2900, a ECC81 equivalent.

This is all, of course, just a very subjective experience....

Cheers,


P.S. If anyone has done tests using a spectrum analyser, I'd like to hear about it...
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Old 23rd February 2004, 12:57 PM   #6
EC8010 is offline EC8010  United Kingdom
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I know I've got some A2900 somewhere, but can I find the the little so-and-sos?
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Old 23rd February 2004, 01:05 PM   #7
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Hi,

Quote:
but can I find the the little so-and-sos?
Don't know what types you're looking for but as you're near Big Ben, maybe Langrex might still carry some obscure NOS types?

Not too sure, but I think Colomor is close to London as well.

Whenever possible I try to buy my stuff " on the spot", in that way you at least can have a "visual inspection" before splashing out the hard earned greenbags...

Cheers,
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Old 23rd February 2004, 01:36 PM   #8
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Hi Frank,

Would like to ask one question.

For a comparison of GEC A2900, CV455 and Genalex B739, will there be any difference on the sound?

Rgds,
Red

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Old 23rd February 2004, 01:45 PM   #9
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Hi,

Quote:
For a comparison of GEC A2900, CV455 and Genalex B739, will there be any difference on the sound?
The CV number could be anything as it is just a Civilian Wartype code number.

IME, between so called quasi equivalents there are always differences as there are subtle differences in manufacture and materials used.
There are audible differences between manufacturers and even batches from the same manufacturer.

Some differences are subtle, others not so subtle at all.

Whether these are audible in a given system will much depend of the resolving power of that system.

My fav tool for critical listening is the Stax Lamba Pro Electrostatic headset which is a very revealing toy.

Cheers,
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Old 24th February 2004, 12:14 AM   #10
EC8010 is offline EC8010  United Kingdom
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Actually, CV stands for Common Valve; that's to say that it is common between RAF, Navy and Army, whereas each service had previously specified their own valve types. Only in Britain...
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