[Oskari]

  Thanks for the info and the pictures. The tube I have does not match any of the pictures - especially the mica plates are different.

 
You are close to the answer when you find a branded one that is an exact match.
 

I guess it is safe to say that it was made by MaHiTo

 
Or TeNeMaHiTo. 

 

[Oskari]

  The raised marker on the glass underside is not very clear, but is visible enough ...

 
I see your 'marker' wasn't exactly the thing I thought it was. 

 

[Oskari]

 
Yes, 1969 makes the most sense to me. The only thing that seems a bit off is this implies there were only 4 revisions since the tube was introduced some 20 years earlier. But since the tube seems not to have been nearly as important to Philips as tubes such as the ECC82 and ECC88, then I would guess it is likely that very few resources were devoted to its development and improvement over that period of time.

 
Sounds plausible. There probably was a limited replacement market for which batches were produced only every now and then.

 

[gibosi]

My ECC40 to 6DJ8 adapter arrived yesterday and I was able to spend a couple hours with the Philips ECC40 last night. This is a seriously good tube folks. My go-to tube recently has been the small-bottle Sylvania 6SN7W, and this ECC40 is just as good.
 

Spoiler: 1945 Small bottle Sylvania 6SN7

 
As a colleague likes to say, the differences are not black and white, but shades of gray. The Sylvania is just a tad bit darker and the Philips is just a tad bit brighter, but otherwise, from top to bottom, both of these are top-tier.
 
Philips manufactured these tubes in at least three factories. La Radiotechnique, Chartres, Valvo Hamburg, and either CIFTE (Compagnie Industrielle Francaise Des Tubes Electroniques) or Philips, Sittard. I have seen Mullard ECC40/CV3884 on eBay, so perhaps Mullard also manufactured these tubes. The tube codes are typically etched into the foot of the tube around the pins.
 
My tube - La Radiotechnique, Chartres (I am pretty sure the factory symbol is a + with an underline, that is "+", and not the Siemens symbol). I have seen Philips and Siemens tubes with these codes.
 

 
Valvo, Hamburg (Factory symbol = D). I have seen a Siemens with this code, so I don't think Siemens manufactured this tube.
 

 
CIFTE. (factory symbol = malformed "t") or Sittard, Holland (factory symbol "+") I am inclined to think it is CIFTE, as I think Sittard would more likely have used the standard Philips format, FYMW. Further, I have seen two Darios with this code, which again leads me to think CIFTE France production.
 

 

[Oskari]

  CIFTE. (factory symbol = malformed "t") or Sittard, Holland (factory symbol "+") I am inclined to think it is CIFTE, as I think Sittard would more likely have used the standard Philips format, FYMW.

 
Both are Philips formats, 'old' code (from 1948 to 1955 or 1956) and 'new' code (later on) as described by Blake. The week was added to the 'new' code in about 1961. 
 

1. http://tubedata.milbert.com/other/Philips/PhilipsCodeListAB-v10.pdf

 

[gibosi]

  Both are Philips formats, 'old' code (from 1948 to 1955 or 1956) and 'new' code (later on) as described by Blake. The week was added to the 'new' code in about 1961. 
 

1. http://tubedata.milbert.com/other/Philips/PhilipsCodeListAB-v10.pdf

 
Thanks! The info on 'old' code tells me that the Hamburg tube, above, was manufactured in September, 1953. And it now seems likely that "+" indicates the Sittard, Holland factory, and that tube was manufactured in March, 1953.
 
And just today, I learned that the ECC40 was also manufactured in the La Radiotechnique, Suresnes factory and the Thorn-AEI Radio valve Co. Ltd. (Ediswan) factory. The Suresnes and Ediswan tubes I saw carry the Mullard label and were manufactured in the 1970s (LC5 F2J4 = 1972 and LC5 I8H2 = 1978).
 
So it appears the ECC40 was manufactured for a period of time lasting at least 30 years, starting in 1948, in at least 5 different Philips factories, plus Tungsram....
 
Happy rolling! lol

 

[mordy]

Hi,
 
Seems that part of the performance of a vacuum tube is resistance to internal vibration. If vibration/oscillation of internal components can be prevented or minimized, it should result in less micro-phonics and better sound.
 
Read somewhere that the "mouse ears" on the top mica on some Tung Sol octal tubes were made in an attempt to brace the internal components against the glass envelope, but the writer claimed that it did not work.

 
Here is a picture of a 6CG7 tube with spring loaded C-clamps on the top mica to clamp down the internals:
Here is another tube from my  6SN7 260 stash: It is labeled Hoffman Easy Vision. The number 274 indicates that it was made by RCA; the manufacturing date is Sept 1965. On the top mica is a an interesting mounting of the heaters with a wire connecting them:
 


(Hoffman was a California based company that made TVs from 1948 - 1977).
 
Anybody knows the purpose of the wire arrangement on the top mica?
 
Finally, there are lots of ads on Ebay for damping rings:

 
 
Snake oil, or do they help?
 
"Madam, you car needs to have the muffler bearings greased".  lol....

 

[mab1376]

Snake oil, or do they help?  
"Madam, you car needs to have the muffler bearings greased".  lol....

 
My 6HM5 are extremely microphonic with my T70's since they are so sensitive. if you tap it with your nail you can hear a high pitched ring like a bell. I think it would stop that but not much else. Probably not a good idea to be tapping tubes anyway while they're on anyway.
 
I can notice the ring as music starts too and stays there subtlety in the background. Don't notice it at all with my HD650's.

 

[gibosi]

This link was posted over in the Schiit Lyr Tube Rollers thread, but think it deserves a wider posting.

http://www.ominous-valve.com/hifi.html
 
"It's a movement. It's the Mister Valve anti-sonic-massacree movement, and you're in it."

 

[kvtaco17]

My adapter for 6SN7's arrived! Rolled in the Sylvania 6SN7GTB I have and so far so good... such sound, much dynamic... wow lol
 
Really diggin this setup so far... BUT how will it compare to my trusty US Raytheon 6CG7? More to come!

 

[gibosi]

  My adapter for 6SN7's arrived! Rolled in the Sylvania 6SN7GTB I have and so far so good... such sound, much dynamic... wow lol

 
Welcome to 6SN7 land! But watch out, these tubes can be addictive! lol 

 

[CollectoR13]

My siemens C3GS and sylvania 6sn7gt arrived!
I am usually not that into looks, but this tubes are looking so beautiful!
I am so desperate to try them, but unfortunally my Sockets for the C3GS didn't arrive yet...
Now I have to build everything together into a clean black case, I hope the silver wire I bought is not too stiff, hopefully it will serve its purpose.
I will make a table for the 6n6p to 6sn7 conversion, could anyone correct it if its wrong?
I will uplpad it soon!

Thanks guys!

 

[CollectoR13]

This is my conversion table for 6n6p to 6sn7!
I would appreciate if you tell me if there is anything wrong with it!

 
BTW, what does S in a tube diagram mean?

 

[gibosi]

  This is my conversion table for 6n6p to 6sn7!
I would appreciate if you tell me if there is anything wrong with it!

 
BTW, what does S in a tube diagram mean?

 
Your conversion table looks fine to me.
 
S = Shield. The 6N6P (and 6DJ8) have a metal shield between the two triodes while the 6SN7 does not. And so in this translation, you can ignore pin 9.

 

[CollectoR13]

Thank you very much for your help, gibosi!
I wanted to stay on the safe side, not that I blow up those sylvanias lol...