Thanks, Ed, you're absolutely right; I recognized I needed....

Posted by radiance (M) on July 7, 2006 at 11:06:39

In Reply to: really need to work on facts before posting posted by Ed Sawyer on July 7, 2006 at 10:00:56:

...to change my evil ways with that ignorant response to Mark.

What I did not understand, but do now, is that there are vast differences between materials different manufacturers use for different tubes at different times; this appears to be especially true for alloys used in cathodes and filaments - I made the huge error of assuming tube fabrication materials were the same for a particular tube, and then compounded it by getting the erroneous impression early on that DHT's were tungsten based, indirectly heated were oxide coating based, etc, etc....

...when in fact manufacturers appear to make lots and lots of changes and substitutions for apparently a multitude of reasons.

Rather than this futile attempt to categorize and generalize - now that I see the true complexity of the whole thing - I see now it would be better to try to understand whether cathode composition actually makes a sonic difference.

I don't know if the sonics of a tube depends upon whether it's directly or indirectly heated, whether tungsten or molybenum or thorium or various oxides are used, and I would really like to know if anyone has strong opinions on this subject based in a real knowledge of the subject. Because there are so many variables in the design, construction, materials and use of a tube, it may not be possible to easily make any sonic judgements based on cathode design and materials;

FWIW what I can do that would be more helpful is to pull together the opinions of authors such as Tomer and Kohl and Rosebury and the ARRL and RCA, quoting with careful citations, on a few topics that seem to come up repeatedly on the forum:

voltage tolerances
starving cathodes
AC vs DC
delayed B+

in terms of categorizing tubes by cathode/filament type, I think the only thing that needs to be done is to recognize and list the relatively few that are thoriated tungsten - which do have slightly different "rules" for the filament - and recognize that virtually all the rest of all the types of tubes used for audio fall into the "non-thoriated tungsten" group. For example, in terms of voltage tolerance and starving, it may not make much difference whether the cathode is directly or indirectly heated if in either case the emitting layer is an oxide based coating; with oxide based coatings, over-voltage can be damaging, starving is permissible, delaying B+ may in some cases prolong tube life, and I don't know yet the whole picture about AC vs DC.

Thanks for your friendly and correct admonishion.

"It ain't a comeback until it's left the shop" Jimmy Dunne, the first man to drive a VW Beetle faster than 200 mph, and he has the forehead scar to prove it; I will always honor him for taking a chance on me when I wanted to be an engine mechanic.

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Follow Ups Full Thread

Topic - is it advisable to run the heater lower than specs? - jarthel 19:50:18 07/05/06 (37)

Re: is it advisable to run the heater lower than specs? - Victor Khomenko 08:34:23 07/06/06 (0)

That's not lower than spec - ffrr 01:07:28 07/06/06 (3)

not all tube datasheet has a +/- on the heater specs though - jarthel 03:36:54 07/06/06 (2)

Re: not all tube datasheet has a +/- on the heater specs though - ffrr 04:07:48 07/06/06 (1)

Re: not all tube datasheet has a +/- on the heater specs though - PÃ¤r 06:30:19 07/06/06 (0)

My call; - Poindexter 19:59:09 07/05/06 (30)

On indirectly heated tubes... - Ivan303 20:04:36 07/05/06 (29)

Yes; my apologies. - Poindexter 10:03:30 07/06/06 (1)

Re: never used a DHT - Ivan303 10:12:59 07/06/06 (0)

according to my reading, it all depends upon whether.... - radiance 21:59:22 07/05/06 (26)

2A3, 300B, 45 all have semiconductor cathodes. - Mark Kelly 17:32:42 07/06/06 (12)

OOOPS! APOLOGIES!! I take it back, you're right. Here's the scoop: - radiance 18:30:13 07/06/06 (9)

really need to work on facts before posting - Ed Sawyer 10:00:56 07/07/06 (2)

Thanks, Ed, you're absolutely right; I recognized I needed.... - radiance 11:06:39 07/07/06 (1)

Re: If I may help... - Dave-A 19:50:03 07/07/06 (0)

10 - Mark Kelly 18:56:19 07/06/06 (5)

Just to confuse things... - jub_jugs 01:41:47 07/07/06 (3)

Yeah, long plated some WE's - Ivan303 07:22:17 07/07/06 (2)

if you were designing the perfect SET tube, would you... - radiance 11:11:26 07/07/06 (1)

Re: Designing the perfect SET tube, I would... - Dave-A 19:20:42 07/07/06 (0)

thank you, I have saved the data sheet; I had found... - radiance 21:06:38 07/06/06 (0)

thanks for the cool spectrum, Mark, but there is a..... - radiance 17:56:30 07/06/06 (1)

continued apology for my really ignorant post....... - radiance 23:13:46 07/06/06 (0)

Re: Thoriated tungsten - Dave-A 07:37:34 07/06/06 (12)

Are you sure about that? - Mark Kelly 17:45:12 07/06/06 (7)

Re: Have you looked at your 211's....? - Dave-A 19:34:51 07/07/06 (6)

I'm not picking nits. - Mark Kelly 20:18:26 07/07/06 (5)

Re: I'm sorry I forgot about the drains... - Dave-A 21:09:14 07/07/06 (4)

Now I see the problem - Mark Kelly 23:06:23 07/07/06 (3)

Re: Another example - Dave-A 06:27:29 07/08/06 (2)

Just for consistency - Mark Kelly 16:11:40 07/08/06 (1)

Re: Just for my understanding... - Dave-A 09:34:21 07/09/06 (0)

wow, great questions!! don't know, but will find out. will..... - radiance 14:43:55 07/06/06 (0)

what Dave said about Thoriated tungsten - JJ Triode 10:13:44 07/06/06 (2)

hmmm.....there's a mystery here; when I get the time to dissect.... - radiance 17:35:38 07/06/06 (0)

Re: Yes, 845 and 211 both. - Dave-A 12:50:02 07/06/06 (0)

Follow Ups

Thanks, Ed, you're absolutely right; I recognized I needed.... - radiance 11:06:39 07/07/06 (1)

Re: If I may help... - Dave-A 19:50:03 07/07/06 (0)

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