Looking for info on 6ca7/el34 tubes

mdittman

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I'm hoping some of you with greater tube knowledge than me can help identify the manufacturer of these tubes. They're branded National. I've read online where most people say they were made in Germany by RTF but all those say made in Germany on the base. These say made in England. I bought a box of 5 NOS of these from someone who was liquidating his father's collection after having to put him in a home.
I was thinking of using these in a Marshall Master PA amp I traded for a month or so ago. Do you think these will work well in this amp? Thanks.
IMG_20200526_115630957.jpg
 

mdubya

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They should work if it is an EL 34 type amp and the tubes are good. You won't know how they sound until you try them. 6ca7 are part of the EVH mythology. I have A/B'd them with EL 34's before. They sounded about as different as you would expect any 2 sets of very similar tubes are likely to sound, i.e, different but nothing earth shattering.
 

ivan H

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I just noticed this thread, & to work out exactly what tubes you have we'll require more info & close-up pics, but I can tell you that they are an actual EL34 & not a true 6CA7. To explain, we'll need to get into a little tube history. Tube "rebranding" was common practice in the industry. The EL34 is a British (Philips Mullard) designed "pentode" type tube. The 6CA7 is a USA designed (Sylvania??) Beam Tetrode type tube made by Sylvania, GE, RCA etc. These two types are equivalents (as is the KT77) & can be substituted without any problems, so we often see tubes labelled as EL34/6CA7. The EL34 typically has the tall, thin bottle as seen in your pic above. The (true) 6CA7 beam tetrode has what came to be called a "fat bottle" as can be seen below
15908944689292222473232125324751.png
15908942811995591831927250789690.png

Note the very different plate structure between the tubes in the OP's pic & the 6CA7's shown above.
Looking at the OP's tube pic, we can definitely see the plate structure is typical EL34, also that the plates are "crimped" rather that (spot) welded. It has a single "halo" getter. Looking at the black base, we can just make out a hole in the center of the base of the guide pin. Mullard tubes had this hole in the base of the guide pin, but not exclusively as other manufacturers also did this.
To help identify your tubes, look for production date codes etched (or printed) on the glass bottle, usually around the bottom portion of the bottle. Some close-up pics of the tubes internal structure would also help possible identification. They could possibly be later production Mullard, like xf3, xf4 or xf5, or from one of the other British manufacturers. Brimar was a major EL34 manufacturer.
Here's an example of "rebranded" Mullards (from my "Black Flag" JTM50 build)
WP_20190301_19_36_02_Smart.jpg

& their boxes
WP_20190301_19_34_39_Smart.jpg

Note the "spot welded" plate structures.
The tube type designation (xf2) & the (matching) date codes B2J3 can be seen near the bottom of the glass bottles. The date code tells us the tubes were manufactured at the Blackburn plant (B), in 1972 (2), in the month of October (J), & in the 3rd week of that month (3).
The second digit, (2) could indicate a year of manufacture of either 1952, 1962 or 1972.
We know it's 1972 from the black base material. This came into use '69~'70.
Hopefully we can work out exactly what type EL34's you have. One thing you can count on regardless of manufacturer, they'll be typical British audio valve quality. Cheers
Edit:
FWIW, EVH used Sylvania 6CA7's. Cheers
 
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irocdave12

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I'm hoping some of you with greater tube knowledge than me can help identify the manufacturer of these tubes. They're branded National. I've read online where most people say they were made in Germany by RTF but all those say made in Germany on the base. These say made in England. I bought a box of 5 NOS of these from someone who was liquidating his father's collection after having to put him in a home.
I was thinking of using these in a Marshall Master PA amp I traded for a month or so ago. Do you think these will work well in this amp? Thanks.View attachment 464882
Your tubes are in fact RFT tubes made in germany. East Germany specifically. Many times you’ll hear them as being made by Siemens also as they had a distribution deal with RFT. They are easily identified by the unique dimple in the top and are called dimple tops by a lot of people. National was a tube rebranding company and having stamps of country origin that are also wrong is very common. I have a set of tubes that were actually made in Yugoslavia rebranded by someone and stamped made in England only to be eventually distributed by RCA and getting their label as well. So it can be very confusing unless you know what to look for. These RFT tubes are a favorite of the Marshall crowd and usually sound quite good
 

mdittman

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Your tubes are in fact RFT tubes made in germany. East Germany specifically. Many times you’ll hear them as being made by Siemens also as they had a distribution deal with RFT. They are easily identified by the unique dimple in the top and are called dimple tops by a lot of people. National was a tube rebranding company and having stamps of country origin that are also wrong is very common. I have a set of tubes that were actually made in Yugoslavia rebranded by someone and stamped made in England only to be eventually distributed by RCA and getting their label as well. So it can be very confusing unless you know what to look for. These RFT tubes are a favorite of the Marshall crowd and usually sound quite good
Thanks for the info. I paid $90 for five NOS ones that have matching numbers (I assume someone checked them) written inside the top flap of the box. That's about what a quad of average run of the mill ones go for so I assume it was worthwhile.
 


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