The 6SN7 Identification Guide

[sennfan83261]

Thanks for playing along guys, much appreciated! No one's close.

If someone gets it right, does that person get the tube amp that's pictured in your post?

 

[cddc]

Here's a riddle for everyone!
Haven't found a picture online of a second specimen, that's why it's here for you!

I'm a warm sounding European SN7 and I lack controlled heater warm-up.
What am I?

This is definitely a weirdo 6SN7.

It is definitely not a Brimar, as Brimar comes with round plates but this one has flat plates.

Fivre does come with staggered plates, but it normally comes with clear glass, and its top mica is much narrower, so not likely a Fivre as well.

I was initially going to guess it’s a Philips/Pope tube out of Holland, given Tom’s European background (very likely from Holland as well, right?). I have seen some RCA grey glass like tubes that are actually Holland-made Philips, but these Philips tubes come with parallel flat plates instead of staggered plates as shown.

Now, from the tube-on-amp pic I’ve known it’s a British tube, as the pic shows the CV logo for British military. And the brown base looks like some BVA tubes. So is it a Mullard or GEC tube? But I’ve seen GEC/Marconi/Osgram 6SN7’s (aka B65’s), and these do not have staggered plates. Also, Mullard never made any 6SN7 tubes as far as I know. So is it an engineering sample from the BVA group?

 

[Tom-s]

Last weekend I rebuild the previously pictured self build 1626 Darling amplifier (also found on this forum, sold as Amps and Sound Kenzie) that's doing speaker duty in my study.
I rewired the driver section from 12SL7 to 12SN7 (Led bias, CCS@4ma) and started looking around my collection for 12SN7's when this tube was found in one of the boxes.
Yesterday (see pictures) the Darling amp had it's small blue Edcor on there, starting today it's singing with massive AE transformers (build for 300b kind of power).


I scratched my head a little as I had never seen a tube like this.
CV925 made in Tottenham UK, with broad arrow and a Tottenham top mica plate.

Here's a CV1932 Mullard made in Tottenham (6J5 for US) mica for comparison, notice the similarities?
So that's half a SN7, and we agree you can buy actual 6J5's made by Mullard.



It also wears the Philips tube code 0K1 (12SN7) J5F (Tottenham June 1955?).

So is it SN7? An unexpected coincidence or confirmation of this came at it's bottom (as with other Philips / Mullard tubes).

The writing here says 2SN or 28N, but i like to read 2SN as a way of telling a 12SN7.




So, is it a true SN7 and not a 33 or 32 equivalent like Mullard is known for?
Here's the test results and traced curvers of the actual tube -> It's a true 12SN7!



@cddc You were really close! Good thinking!
As far as i know Philips Heerlen/Eindhoven factories never did a 6SN7. I have a bunch wearing all sorts of Philips type labels, with RCA type build.
And the type B65 in my collection is staggered plates (can't get it in a picture because of the black coating).

 

[bcowen]

This is definitely a weirdo 6SN7.

It is definitely not a Brimar, as Brimar comes with round plates but this one has flat plates.

Fivre does come with staggered plates, but it normally comes with clear glass, and its top mica is much narrower, so not likely a Fivre as well.

I was initially going to guess it’s a Philips/Pope tube out of Holland, given Tom’s European background (very likely from Holland as well, right?). I have seen some RCA grey glass like tubes that are actually Holland-made Philips, but these Philips tubes come with parallel flat plates instead of staggered plates as shown.

Now, from the tube-on-amp pic I’ve known it’s a British tube, as the pic shows the CV logo for British military. And the brown base looks like some BVA tubes. So is it a Mullard or GEC tube? But I’ve seen GEC/Marconi/Osgram 6SN7’s (aka B65’s), and these do not have staggered plates. Also, Mullard never made any 6SN7 tubes as far as I know. So is it an engineering sample from the BVA group?

@Tom-s didn't say it was a 6SN7. His first post was that it was an "SN7". So either he typo'd or that was intentional, alluding to the possibility it could be a 12SN7. I still don't have a clue what it is, other than possibly an MO-Valve (Marconi/Osram vintage) as GEC acquired MO Valve satisfying at least that part of the mystery.

Edit: Nevermind. I was minute too late posting. LOL!

 

[cddc]

I know as soon as someone (intentionally/unintentionally) drops the number before SN7, it’s very likely a 12SN7 / 25SN7 tube.

They are essentially the same tube with just different heater voltages.

 

[cddc]

Last weekend I rebuild the previously pictured self build 1626 Darling amplifier (also found on this forum, sold as Amps and Sound Kenzie) that's doing speaker duty in my study.
I rewired the driver section from 12SL7 to 12SN7 (Led bias, CCS@4ma) and started looking around my collection for 12SN7's when this tube was found in one of the boxes.
Yesterday (see pictures) the Darling amp had it's small blue Edcor on there, starting today it's singing with massive AE transformers (build for 300b kind of power).


I scratched my head a little as I had never seen a tube like this.
CV925 made in Tottenham UK, with broad arrow and a Tottenham top mica plate.

Here's a CV1932 Mullard made in Tottenham (6J5 for US) mica for comparison, notice the similarities?
So that's half a SN7, and we agree you can buy actual 6J5's made by Mullard.



It also wears the Philips tube code 0K1 (12SN7) J5F (Tottenham June 1955?).

So is it SN7? An unexpected coincidence or confirmation of this came at it's bottom (as with other Philips / Mullard tubes).

The writing here says 2SN or 28N, but i like to read 2SN as a way of telling a 12SN7.




So, is it a true SN7 and not a 33 or 32 equivalent like Mullard is known for?
Here's the test results and traced curvers of the actual tube -> It's a true 12SN7!



@cddc You were really close! Good thinking!
As far as i know Philips Heerlen/Eindhoven factories never did a 6SN7. I have a bunch wearing all sorts of Philips type labels, with RCA type build.
And the type B65 in my collection is staggered plates (can't get it in a picture because of the black coating).

Tom, thanks a lot for those eye candies and tube info, really enjoyed reading them

You really have lots of cool tubes and tube-related stuff … I wish I could live in Europe to have access to these delicious exotic European NOS tubes.

Are you going to turn the amp into a 300B amp, since it's now equipped with transformers capable of driving 300B tubes (thou 300B could be a big pit for anyone's $$$ )?

 

[bcowen]

We had discussed b4. There is no Mullard 6SN7GT. https://www.whatsbestforum.com/threads/mullard-6sn7gt-help-please-info-needed.15277/

They are all made by _______ . hahaha.

I see what you did there. Even confused me for a minute (which is admittedly not terribly difficult).

 

[attmci]

I see what you did there. Even confused me for a minute (which is admittedly not terribly difficult).

It's kind of insane to just show a picture of part of the tube and let others to guess what kind of tube it is. Lesson learned.

 

[Ripper2860]

Cruel and unusual punishment, if you ask me. (And you didn't)

 

[bcowen]

It's kind of insane to just show a picture of part of the tube and let others to guess what kind of tube it is. Lesson learned.

OK, give me my avatar back...you're still confusing me.

 

[attmci]

OK, give me my avatar back...you're still confusing me.

Now, do you want to trade avatar?

 

[JTbbb]

Hello there, I’m fairly new to tube amps and tube rolling and am thoroughly enjoying this aspect of the hobby. However, I have recently bought a couple of tubes and am having trouble working out the date of manufacture. Any ideas? If needed I could do some better photos tomorrow. Thanks in advance.

 

[JKDJedi]

Hello there, I’m fairly new to tube amps and tube rolling and am thoroughly enjoying this aspect of the hobby. However, I have recently bought a couple of tubes and am having trouble working out the date of manufacture. Any ideas? If needed I could do some better photos tomorrow. Thanks in advance.

Those are early to.mid 40's tubes

 

[highstream]

Depending on the application and condition of the tubes, those should sound very nice.

 

[JTbbb]

Thank you for your help JKDjedi, and yes indeed they sound very nice.

JKDjedi, how do you know the approximate date? Is it from the construction or the code? Just curious.