Mesa el34 str448

[Mike Lamury]

I got the 2 sets of green str448 EL34 from ebay delivered yesterday. Haven't tried them yet. I'm going to call Mesa and see if they recycled the str448 number over the past 20 years. Everything looks good and legit.

 

[bandit2013]

Would like a good picture of the 20 year old STR448 tubes. It could also be a Shuguang (Ruby) EL34BSTR or EL34BHT. Both will have a reddish brown base and the size of a 6L6 tube. I have a quad of the EL34BSTR with the Ruby Logo. Not a bad tube. Then again, not sure what is what since Mesa does not have a running list of tubes they had used anymore. Leave you in the dark they will.

 

[Mike Lamury]

Here you go, haven't tried them out yet, I broke my foot and can't really get my amp down rn.

 

[bandit2013]

Interesting. I have no clue who made that tube. The shape of the getter stem is different than the Ruby EL34BSTR or BHT I have seen. Same color base. It almost looks like a JJ 6CA7 but the mica spacers are different. Plates on the Ruby tubes have two oval cuts very much like the STR440 tubes. JJ 6CA7 does have a single rectangular cut out on the plates. If they sound good and work for you, it does not matter who made them. Is the glass bottle the same diameter as the 6L6GC? Or is it just a little smaller? It does appear much larger in diameter than the typical EL34 which makes me think Ruby or Shuguang or JJ.

 

[Mike Lamury]

The glass bottle seems to be the same size as a 6L6

 

[domct203]

I would give a call or email to Mesa to confirm the STR number, from that picture it looks like a 6L6GC.

Dom

 

[Nandrewjackson]

20 years ago? Svetlana ?

 

[domct203]

I’m getting convinced that those are mislabeled 6L6’s, TAD Red Base to be exact. Compare your tubes to the dual getters and plate structure in these pictures:

Here’s Mesa’s pic of the STR-448

And one from a reverb listing:

And your tubes:


You should definitely reach out to Mesa on this one.

 

[Mike Lamury]

Mine do have the 2 holes in the center metal part and does Also have the 2 getters but the small metal part that extends from the side on mine doesn't have the winged looking part sticking off if it like pictured on the 6L6 pics above. Everything else looks the same except the metal wing things sticking out to the side inside the tube.

 

[domct203]

I did find this thread on the board, looks like they could be older tubes.

https://boogieforum.com/threads/new-mesa-str-448-el34.59396/
There is really not much info on the web about this.

I think you should still contact Mesa. They might be old stock tubes, but the lack of available info is odd if they are indeed an old stock Mesa branded tube. I’m not sure if they recycle STR numbers across tube types.

I still think they are a 6L6GC, or maybe 6CA7, if they are 6CA7, it’s odd that Mesa would mark them EL34.

Dom

 

[tbonesullivan]

Part of my brain remembers something about 6L6 tubes that ran so hot they just labeled them as EL34s? How many pins does the base on those tubes have?

It seems odd that Mesa would use the same STR designation for both an EL34 and 6L6GC tube, unless they were the same tube.

 

[domct203]

If I remember correctly the 6L6GC does not use pins 1 & 6, an EL34 will always have pin 1.

I don’t have Mesa tubes with me right now to confirm.

I believe most current tube manufacturers do not put the pins in unused positions.

Do your tubes have pin 1? The timing notch is between pins 1 & 8.

Dom

 

[Mike Lamury]

It has all the pins on the bottom, it looks like they're all connected to something inside. Pin #1's contact goes straight up connecting to the big metal part inside the tube. Here's some pics.

 

[domct203]

If pin 1 is connected they are EL34’s, or some other power pentode design tube. Pin 1 is connected to the suppressor grid, which is not used in a 6L6 design, a beam tetrode tube. Pin 6 is not used in either octal socket design.

The envelope on those tubes seem big for EL34’s, I’m curious who makes them.

Dom

 

[domct203]

I sent Mesa a message via their zen-desk asking if they also made an EL34 with the STR-448 designation. If they reply I’ll let you know.

I haven’t reached out to them since Gibson acquired them, before that they didn’t work in the office on Friday, and would take a few days to reply. Let’s see how Gibson handles it’s customer requests.

Dom

 

[Mike Lamury]

If pin 1 is connected they are EL34’s, or some other power pentode design tube. Pin 1 is connected to the suppressor grid, which is not used in a 6L6 design, a beam tetrode tube. Pin 6 is not used in either octal socket design.

The envelope on those tubes seem big for EL34’s, I’m curious who makes them.

View attachment 1951

View attachment 1952

Dom

After comparing to my tubes more Closely I think it's the EL34. #1 IS clearly connected to the filament and #6 isn't connected to anything and #'s 2&7 looks like they are connected the same as the diagram.

 

[bandit2013]

Those are EL34 big bottle tubes. JJ has made them as well as Shuguang. The tube diameter of the STR447 EL34 has the smallest diameter, where as a 6CA7 does not, those are generally larger. TAD did have some EL34 with a brown base made by Shuguang. They were the EL34B model.

https://www.tubeampdoctor.com/en/el34-b-str-tad-premium-tube/valve?c=76
However, the mica spacers are shaped differently. May not mean anything but could be a different tube. Ruby version has a larger bottle too but more on the same size as a SED =C= EL34 tube. Not the same diameter as a 6L6GC tube.

The Tung Sol EL34B also has a brown base and looks similar but glass is not as large as a 6L6 and only has a single getter on a bridged wire between the plates. I assume those STR448 tubes are Shuguang made for TAD but private labeled for Mesa so the base does not have TAD Germany on the bottom.

There are not many companies that make tubes. Reflektor, Shuguang/Sino, JJ tubes, and Svetlana (they stopped production of audio tubes back in 2013 I believe). My hunch it is a Shuguang tube made to TAD specifications but with different mica spacers.

As for other tube manufacturers, the newest one on the market is PSVane. They are a spin-off of Shuguang/Sino that are making the Mesa STR448 6L6GC tube for TAD redbase.

 

[Mike Lamury]

Those are EL34 big bottle tubes. JJ has made them as well as Shuguang. The tube diameter of the STR447 EL34 has the smallest diameter, where as a 6CA7 does not, those are generally larger. TAD did have some EL34 with a brown base made by Shuguang. They were the EL34B model.

https://www.tubeampdoctor.com/en/el34-b-str-tad-premium-tube/valve?c=76
However, the mica spacers are shaped differently. May not mean anything but could be a different tube. Ruby version has a larger bottle too but more on the same size as a SED =C= EL34 tube. Not the same diameter as a 6L6GC tube.

The Tung Sol EL34B also has a brown base and looks similar but glass is not as large as a 6L6 and only has a single getter on a bridged wire between the plates. I assume those STR448 tubes are Shuguang made for TAD but private labeled for Mesa so the base does not have TAD Germany on the bottom.

There are not many companies that make tubes. Reflektor, Shuguang/Sino, JJ tubes, and Svetlana (they stopped production of audio tubes back in 2013 I believe). My hunch it is a Shuguang tube made to TAD specifications but with different mica spacers.

As for other tube manufacturers, the newest one on the market is PSVane. They are a spin-off of Shuguang/Sino that are making the Mesa STR448 6L6GC tube for TAD redbase.

So are these generally good tubes in your opinion? Thanks for clearing that up before I put them in my amp.

 

[Mike Lamury]

The seller said he had plenty of these in different color codes if anybody is interested lookup the seller on eBay they were $59.99/pair; The seller is; lesliehammtech

 

[clyvediggins]

Being bigger bottles, would those fit in TC100?
I’m new to tube swapping, looking for a replacement set when the time comes. Thanks for all the info.