I found 3 of these EL34's in a guitar amp. Wondering if they would work well in a Hifi amplifier?
Printed in gray on the glass it says:
6CA7
EL34
USA
They have black bases with red printing:
RCA ABA
GN
They have two getter at the top at 45 degree angles and one on the side. Here are a couple of pictures:
Any info is greatly appreciated.
Printed in gray on the glass it says:
6CA7
EL34
USA
They have black bases with red printing:
RCA ABA
GN
They have two getter at the top at 45 degree angles and one on the side. Here are a couple of pictures:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Any info is greatly appreciated.
If the tubes are still good, you can use them in the KT88 SE amp you are building. No changes need to be made to the circuitry.
Thanks Scott. I am thinking about trying them in your design.
I was just wondering if these were just average tubes or possibly something special. I forgot to mention that the guitar tube head I pulled them out of is a fully functional Music Man One Thirty (huge power and output transformers and a pretty healthy chokes). The forth output tube is different than those 3. Narrower diameter envelop and what I can read on the glass says:
6C <something rubbed off> C
ELECTRONIC ENTERPRISES, INC.
MADE IN ENGLAND
It has one getter at the top.
Thanks.
I was just wondering if these were just average tubes or possibly something special. I forgot to mention that the guitar tube head I pulled them out of is a fully functional Music Man One Thirty (huge power and output transformers and a pretty healthy chokes). The forth output tube is different than those 3. Narrower diameter envelop and what I can read on the glass says:
6C <something rubbed off> C
ELECTRONIC ENTERPRISES, INC.
MADE IN ENGLAND
It has one getter at the top.
Thanks.
If the Music Man was fully functional there will be four EL34's (6CA7). The 6CA7 is the light weight verion.
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What you have is the American 6CA7. Made differently from the EL34.
6CA7 to EL34 [Archive] - The Gear Page
Check out the link. They talk about the differences. I tried to look up a data sheet but only the "EL34" data comes up. The 6CA7 was one of the last tubes that GE/MPD made before they closed. I dont think its a true pentode; the internal structure looks more like a 6550 than an EL34.
Hope this helps...
Daniel
6CA7 to EL34 [Archive] - The Gear Page
Check out the link. They talk about the differences. I tried to look up a data sheet but only the "EL34" data comes up. The 6CA7 was one of the last tubes that GE/MPD made before they closed. I dont think its a true pentode; the internal structure looks more like a 6550 than an EL34.
Hope this helps...
Daniel
Here is a data sheet link for the 6CA7 made by Tung-sol:
http://frank.pocnet.net/sheets/127/6/6CA7.pdf
From what I've read, the 6CA7 is a beam tetrode with different G3 construction. Both have G3 available as an external connection. The 6550 and the KT88 both have G3 tied internally to the cathode.
I have both the EL34 and the 6CA7 by Electroharmonix. The EL34 is in a slimmer bottle.
Since the tubes can be used interchangeably your 4th tube is probably an EL34.
http://frank.pocnet.net/sheets/127/6/6CA7.pdf
From what I've read, the 6CA7 is a beam tetrode with different G3 construction. Both have G3 available as an external connection. The 6550 and the KT88 both have G3 tied internally to the cathode.
I have both the EL34 and the 6CA7 by Electroharmonix. The EL34 is in a slimmer bottle.
Since the tubes can be used interchangeably your 4th tube is probably an EL34.
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A 6CA7 is a Power Beam Pentode, as is an EL34.
They are electrically similar.
See http://www.thetubestore.com/JJ-6CA7
They are electrically similar.
See http://www.thetubestore.com/JJ-6CA7
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True EL34 are pentodes. 6CA7 is an equivalent beam tetrode. Mislabelling may occur, either way round.
Yes, I agree about mislabeling. It happens from time to time. The nearest explanation I have come across is that a 6CA7 is "Similar" to an EL34 but not the other way around. That was from Mullard back in 1972 when I had a problem sourcing EL34s. The screen grid has physical differences as does the cathode. That's all I remember from the conversation.
If a 6CA7 is a beam tetrode it doesn't have a screen grid. The beam tetrode was developed by RCA to avoid paying Philips a patent fee for making pentodes. Also I don't think the EL34 is an "English" design as it was developed by Philips in the Netherlands. It may be that the best EL34s were made by Mullard in their Blackburn factory, but that's a different story.
No. A beam tetrode lacks a suppressor grid. Beam tetrodes have a screen grid - indeed it is the interaction of the screen grid and anode with secondary electrons which makes the pentode or beam tetrode necessary.
The beam tetrode was invented by Marconi-Osram (GEC) in the UK, but then developed further by RCA.
The beam tetrode was invented by Marconi-Osram (GEC) in the UK, but then developed further by RCA.
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Yes, of course you're right. Must remeber to put brain in gear before writing. On the other hand, although the beam tetrode was invented here by 2 EMI engineers the M-OV company decided not to put it into production and handed the development work over to their partners, RCA in the US, who did all the detailed production work.
M-O did produce beam tetrodes such as KT66 and KT88. Later KT77, which is another EL34-alike. I understand they found problems, though; perhaps in making smaller valves? I have noticed that many US RF 'pentodes' are in fact small beam tetrodes, so I think it was reliability and ease of manufacturing which RCA added.
Later, I suspect that European valve makers started using at least partly aligned grids in pentodes to reduce screen current and so improve efficiency in output stages and reduce partition noise in small signal valves.
Later, I suspect that European valve makers started using at least partly aligned grids in pentodes to reduce screen current and so improve efficiency in output stages and reduce partition noise in small signal valves.
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Yes they did but, from what I've read, only after their close partner RCA had proved that beam tetrodes could be reliably mass-produced. KT66s were produced before the Second World War (I have a 1937 M-OV catalogue with them in) but I don't think there were any KT88s until after it and the KT77 was the last to be developed, precisely to combat the EL34 which, I think, was first produced by Philips in the early 1950s
Yes, you may be right. The EL34 is a rather late pentode design, although it follows a long line of ancestor output pentodes. Curiously, some Americans seem to believe that the EL34 was an early pentode which Philips invented to get round RCA patents!
Assuming the tubes I have are in fine working order, how would they compare to a new production EL34 like JJ is producing?
A safe general rule is that NOS valves in good condition are likely to be more reliable and adhere more closely to datasheet behaviour than modern ones. Like any general rule, there may be exceptions.
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