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Old 6th March 2013, 01:40 PM   #1
PWR RYD is offline PWR RYD  United States
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Default Are these EL34's good?

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:

Click the image to open in full size.

Click the image to open in full size.

Any info is greatly appreciated.
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Old 6th March 2013, 05:47 PM   #2
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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.
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Old 6th March 2013, 10:05 PM   #3
PWR RYD is offline PWR RYD  United States
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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.
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Old 6th March 2013, 10:07 PM   #4
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EL34 lovelly Pentodes. Designed in England many many years ago by Mullard.
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Old 6th March 2013, 10:09 PM   #5
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If the Music Man was fully functional there will be four EL34's (6CA7). The 6CA7 is the light weight verion.

Last edited by JonSnell Electronic; 6th March 2013 at 10:10 PM. Reason: More information
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Old 6th March 2013, 10:27 PM   #6
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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
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Old 6th March 2013, 10:45 PM   #7
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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.

Last edited by scott17; 6th March 2013 at 10:54 PM.
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Old 7th March 2013, 08:09 AM   #8
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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

Last edited by JonSnell Electronic; 7th March 2013 at 08:10 AM. Reason: Addition
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Old 7th March 2013, 10:22 AM   #9
DF96 is offline DF96  England
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True EL34 are pentodes. 6CA7 is an equivalent beam tetrode. Mislabelling may occur, either way round.
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Old 7th March 2013, 10:57 AM   #10
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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.
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