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difference between 6ca7/el34?

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darcyl

New Member
I was wondering what differences there were between 6ca7 and el34 tubes?
Some tell me they are the same, and I have a NOS pair of GE's from the 70's, and they are marked with both, but looking at the PM tubes site, a pair of el34's are $75, but a pair of 6ca7's are only $35? Whats the deal?:music:
 
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6CA7/EL34 is the same tube, a beam pentode with 3 grids. 6CA7 is the american number while EL34 is the european number.

I think someone is trying to rip you off or fool you into thinking that the EL34 is more expensive than the 6CA7, wheras in fact, it is the same tube!

Maybe the seller of the more expensive tube knows that it is a mullard brand compared to a GE brand.

Examples of the same tube:

12AX7/ECC83
6BQ5/EL84
 
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darcyl said:
I was wondering what differences there were between 6ca7 and el34 tubes?
Some tell me they are the same, and I have a NOS pair of GE's from the 70's, and they are marked with both, but looking at the PM tubes site, a pair of el34's are $75, but a pair of 6ca7's are only $35? Whats the deal?:music:
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Unfortunately, due to marketing and other factors, there's some confusion as to what's what regarding EL34 vs 6CA7.

Technically speaking, the old production, US made "fat bottle" 6CA7s are beam tetrodes in that they have only two grid windings. Beam forming plates take the place of g3. They look somewhat like healthy 6L6GCs and the beam forming plates are plainly visible if you you look close. AFAIK, only GE and Sylvania/Philips ECG made these although they were rebranded by others. They're very rugged and apparently have a following in the guitar world. There are current versions being mfgd by Sovtek and others and these too are beam tetrodes.

EL34s are true pentodes in that they have three grid windings and no beam forming plates. They're almost always in tall, smaller diameter bottles compared to 6CA7s. True pentode EL34s have been mfgd just about everywhere but the US.

The confusion between the two types arises from two situations: 1. The beam tetrode 6CA7 and pentode EL34 are usually considered plug compatible equivalents of each other even though the operating principles of the two are slightly different. As a result, many 6CA7s were labeled 6CA7/EL34 as were many EL34s. 2. The US mfgrs and marketers imported and branded Euro and Japanese EL34s as both EL34 and 6CA7/EL34. Net result here is that a US mfgr or marketer could have their name on either type depending on the year and they could be labeled as 6CA7 or 6CA7/EL34

Most claim there are sonic differences betw beam tetrodes and pentodes. I find the differences pretty minor: others don't. But that's another story so won't go into detail here.

As for the price differences @ PM, I can't really comment since I didn't check their site. Based on the prices you note, I'm pretty sure they're selling new mfg and not NOS because the NOS prices for either type are much higher, esp Euro EL34s. If new mfg, I suspect the difference betw the two types is due to relative demand vs mfg volume.
 
Steve O said:
Most claim there are sonic differences betw beam tetrodes and pentodes. I find the differences pretty minor: others don't. But that's another story so won't go into detail here.
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If the amp is designed correctly, there is very little, if any, difference.

If the amp is NOT designed by sound engineering principles (i.e, not using appropriate feedback, not having proper power supply design, not using properly sized transformers and/or proper driver circuits, etc), then there can be big differences in the performance of one type of tube vs. another.

IMHO, those differences are not the fault of the TUBE... but of the DESIGNER, in many cases...

Regards,
Gordon.
 
Darcy:

I do not mean to pry here, but if the PM tubes are the ones I am thinking of, they are simply matched and relabeled tubes. IMO, they are also overpriced. Here is a link to a Canadian supplier of decent brands of tubes at decent prices - their reps can also match tubes based on the make/model of gear or at your request:

www.thetubestore.com

PS...
Check your private messages box.
 
Unfortunately all EL-34s are not created equal. Every manufacturer's EL-34/6CA7 out there sounds slightly different. Sometimes a manufacturer will sell multiple tubes for a given application, and they will attempt to differentiate them with different model numbers. I'm guessing that this is probably the case here.

I would not pay attention so much to the model number of an "equivalent" tube type. Rather I'd be reading up on which make and model people seem to think sounds best inside of your particular amp.
 
The way I have the story is that after Mullard introduced the EL-34, Sylvania wanted in on the action, but could not produce the Mullard tube on account of Mullard owning the patent. So the Beam power tetrode was developed and given the 6CA7 number. Since the Beam Power tube used beam forming plates instead of the EL-34's screen grid, its technology was sufficiently different so as not to infringe the Mullard patent. And since the 6CA7 is a drop-in replacement for an EL-34--works fine in the same circuit--they felt free to label them 6CA7/EL-34. Full disclosure: I read this on the internet some time ago; I suppose it could be wrong, but it sounds plausible to me.
 
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Rob-F said:
The way I have the story is that after Mullard introduced the EL-34, Sylvania wanted in on the action, but could not produce the Mullard tube on account of Mullard owning the patent. So the Beam power tetrode was developed and given the 6CA7 number. Since the Beam Power tube used beam forming plates instead of the EL-34's screen grid, its technology was sufficiently different so as not to infringe the Mullard patent. And since the 6CA7 is a drop-in replacement for an EL-34--works fine in the same circuit--they felt free to label them 6CA7/EL-34. Full disclosure: I read this on the internet some time ago; I suppose it could be wrong, but it sounds plausible to me.
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6CA7 beam tet is a scaled-down 6550, compare them.
 
darcyl said:
I was wondering what differences there were between 6ca7 and el34 tubes?
Some tell me they are the same, and I have a NOS pair of GE's from the 70's, and they are marked with both, but looking at the PM tubes site, a pair of el34's are $75, but a pair of 6ca7's are only $35? Whats the deal?:music:
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Electrically, they are interchangeable.

Soundwise, it might be a different story. In the old days, the 6CA7 had a "harder" vacuum than the Mullard/Amperex EL34. So, the overdrive and compression were different.

In general, the European-made EL34 sounded warmer and smoother. The US-made 6CA7 sounded cleaner at louder volumes. Maybe it's a tad more sterile, too.

Today, the EH 6CA7 is probably one of the tougher construction and cleaner-sounding 6CA7/EL34 types. The JJ is warmer, more old-school European sound.
 
I'm liking the EH 6CA7's a lot. They do have a bit more top end sparkle I guess, but not a sterile sound that I can hear. The bottom end is better than the KT-77's and the EL-34's I've used.
 
Pio1980 said:
Tall & skinny with with prominent wings in the otherwise empty space in top end = EL34 pentode. Shorter & fatter minus empty space with wings = 6CA7 beam tetrode.
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Tall & slender vs. short & fat agrees with my experience. And by "wings" did you mean the Winged C logo? The "C" in "winged C" refers to the original Svetlana brand; the "C"being equivalent to a Russian "S" for "Svetlana." The manufacturing was changed from the original factory to a different one, which acquired the right to use the Svetlana name, but not the Winged C logo. So current production is called Svetlana, but without the winged C logo. I don't think they are as good as the originals.
 
Rob-F said:
Tall & slender vs. short & fat agrees with my experience. And by "wings" did you mean the Winged C logo? The "C" in "winged C" refers to the original Svetlana brand; the "C"being equivalent to a Russian "S" for "Svetlana." The manufacturing was changed from the original factory to a different one, which acquired the right to use the Svetlana name, but not the Winged C logo. So current production is called Svetlana, but without the winged C logo. I don't think they are as good as the originals.
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"Wings", the prominent G1 control grid cooling radiator wings in the otherwise empty space above the pentode element stack.
The 6CA7 beam tetrode has a smaller G1 radiator in a smaller space.
 
I don't know what happened but all the Shuguang 6CA7-Z listings on eBay were deleted today. They were re-posted and prices of these tubes went from $250/quad to $500/quad....
 
I like the RFT EL34s, often called "Siemans". Simans in West Germany purchased RFT tubes from East Germany and put their own label on them. They are quite recognizable as a skinny tube, (skinnier than the base too), and with the 'dimple' on the tube. I used them in Altec 1568s and 1569s. Excellent Tube!! I had 6CA4s in a different amp many years, and liked them very much also. Never tried the newer stuff, so I'm not qualified to offer and opinion. ;>)
 
buffstereo said:
I like the RFT EL34s, often called "Siemans". Simans in West Germany purchased RFT tubes from East Germany and put their own label on them. They are quite recognizable as a skinny tube, (skinnier than the base too), and with the 'dimple' on the tube. I used them in Altec 1568s and 1569s. Excellent Tube!! I had 6CA4s in a different amp many years, and liked them very much also. Never tried the newer stuff, so I'm not qualified to offer and opinion. ;>)
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Siemens
 
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