• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Shuguang EL34-B

Status
Not open for further replies.
Jump to Latest
F

famousmockingbird

Member
Joined 2010
#1
https://www.youtube.com/watch?v=UIBceKSvtcM

http://analogmetric.com/download/Shuguang Beijing Vacuum Tube Datasheet Analog Metric Limited.pdf


Does anyone have any real information on these tubes? I came across a matched quad I don't know what to do with. The datasheet and curves to me looks the same for the A (pentode) and B (tetrode) versions. In the video I linked I can't see the beam plates during the manufacturing process😕

Has anyone ever put this tube on a curve tracer and compared it to a real pentode?

Thanks:hohoho:
 
#2
I too could not see the beam forming elements on the "B" model video either.
By the way, the 6CA7 is listed as a pentode (EL34 equivalent).

If you look carefully at the EL34 tubes you have, you should be able to see whether
it has a real screen grid or beam forming plates.

A pentode has 3 pairs of vertical round support rods for the 3 grids.
Control grid, Screen grid, Suppressor grid.

A beam power tube has the following pairs (starting closest to the cathode, and ending with the plate):
Grid support rods
Screen forming plates (can see flat or curved metal above the mica, not rods)
Supressor support rods

One thing I have seen is for another tube.
An EL84 is a true pentode.
A 6BQ5 is supposed to be a Beam Power tube.
But I have seen some 6BQ5s (at least labeled as 6BQ5s ) that are a true pentode, with
a Screen grid, not beam forming plates.

I believe the pentode versus beam power tubes were originally protected by patents, but
the patents probably have run out.
 
#4
The original 6L6 was a Beam Power Amplifier:
http://tubedata.milbert.com/sheets/021/6/6L6.pdf

The 6L6GC is a Beam Power Tube:
http://tubedata.milbert.com/sheets/049/6/6L6GC.pdf

I made a mistake on my earlier order of the grid vertical rods. It should be:

A beam power tube has the following pairs (starting closest to the cathode, and ending with the plate):
Grid support rods
Screen support rods
Supressor beam forming plates (can see flat or curved metal above the mica, not rods)

7591 is another Beam Power Tube

Here are some drawings that really show the beam forming plates that are connected
to the cathode, as if it is a suppressor grid:
Beam Power Tetrode

And back to true pentodes:
The EL34 and 6CA7 are about the only tubes that bring the suppressor grids
out on a separate pin (pin # 1). It is not internally connected to the cathode.
Don't forget to connect it to the cathode, pin # 8.
 
#6
#8
By the old standards, the tubes were named by/for the number of elements.
If it was a direct heated filament, this was true. For indirectly heated cathodes, the filament and cathode counted as one element (so not strictly true for the total count).
Diode 2, Triode 3, Tetrode 4, and Pentode 5.
Early on, Pentodes had 3 real grids.

But then there were things like patents, improvements, and marketing, etc.
So there were new designs that claimed and/or had advantages. There were new patents, and ways to "bypass" old patents. And as time went on, there were also naming changes (right or wrong). Names and such became blurred.

I believe that RCA had the patent for the first Beam Power 5 element tubes.
A good portion of these were RF tubes. How many have not heard of the 807,
an RF tube that also found audio service as well.

As to grids and screen grids aligning, there were many types. Eimac made Power RF Tetrodes (and many other types too). Some of these Tetrodes had Bird Cage Grids and Bird Cage Screens. The number of "wires" in the birdcage grids and screens were the same; and they were aligned so that the path from the cathode to the plate was a clear path.

Not all pentodes of a particular number, i.e. say EL84s of different manufacturers have exactly the same characteristics.
Not all beam power pentodes of a particular number, i.e. say 6BQ5s of different manufacturers have exactly the same characteristics.

Not even all tubes of the same type number and of one manufacturer have exactly the same characteristics. If that were so, there would be no need for tube matching.

There were ways to make some true 3 grid pentodes and some true beam forming element power tubes have characteristics similar enough that they could be substituted one for the other.

As to how one tube sounds versus another of the same type, I leave that up to the listener.
I think tube rolling is fun, even if you do not hear any difference between some to them,
and especially fun if you do.

Get your sound system set up one particular way, stop making changes for a while, and get ready for Happy Listening.

Merry Christmas. I will be listening to Christmas and Classical Music for now. Jazz later.
 
#9
6A3sUMMER said:
By the old standards, the tubes were named by/for the number of elements.
If it was a direct heated filament, this was true. For indirectly heated cathodes, the filament and cathode counted as one element (so not strictly true for the total count).
Diode 2, Triode 3, Tetrode 4, and Pentode 5.
Early on, Pentodes had 3 real grids.

But then there were things like patents, improvements, and marketing, etc.
So there were new designs that claimed and/or had advantages. There were new patents, and ways to "bypass" old patents. And as time went on, there were also naming changes (right or wrong). Names and such became blurred.
Click to expand...


I look at it similarly. The beam forming plates are still at a potential (connected to cathode internally) and therefore another electrode within the envelope, no? Therefore because the number of electrodes (5) I call it a pentode regardless of patent BS.


zyt said:
Shuguang EL34-B is a beam pentode, has its G2 aligned with G1 to reduce G2 current.

see 5-125B tube.
Click to expand...

Yes but if it is a beam pentode wouldn't it have the beam plates? Which I do not see in the video or looking within the tube itself. Also, according to the Shuguang literature they state the opposite in that G1 and G2 "are not exactly aligned with each other". 😕 Not aligning G1 and G2 is normal for a suppressor grid type pentode no?

So clearly I am not asking the right questions so I will try again. If the tube doesn't have the beam plates how can it be a "beam tetrode"?
 
#10
Again, take a look at:
Beam Power Tetrode

See Fig 1-5 C and D (C is not real clear, but you get the idea)
See Fig 10.22
See Fig 5-21.

You will see that for a true 3 grid wire Pentode, no matter how well you line up the Control Grid with the Screen Grid, it is Not a Beam Power tube.

In a Beam Power tube, Beam forming elements keep the electrons from reaching certain specific areas of the plates.

The closest thing to that in a true 3 grid wire Pentode is that the vertical grid supports shield the electrons from reaching the plates from the specific direction of the cathode to the vertical grid supports to the plate. That shields a very small area on the plate.
Much different to the large area beam forming plate effect.
 
#11
Yes I understand how they work, hence why I don't see how they can call the the EL34-B a "Beam power tube" without the beam forming plates. I also can't see the support rods helping in this regard, too small of an area.

I wonder if a curve tracer could tell us anything. I wish I had one at my disposal.
 
#12
The curves of both designs can in some cases be very similar. Even more similar than from one manufacturer of a design to another manufacturer of that same design. i.e. the design of two manufacturer's Pentode versus Pentode; and the design of two manufacturer's Beam Power versus Beam Power.

Examples are the 6BQ5 Beam Power tube (with real beam forming elements) and EL84 true 3 grid wire Pentode are generally interchangeable.
In fact, I have seen 6BQ5 tubes that are actually (incorrectly) constructed as 3 grid wire Pentodes, even though the original registered JEDEC specs are for Beam Forming elements.

There is a fair amount of variability on curves among different manufacturers of EL34 true 3 grid wire Pentodes.

Given marketing truths and lies, and with fake tubes (that are not really what they are said to be), I think you are better off getting tubes of reliable brands and reliable distributors.

I get some of my tubes from a major distributer in Arizona.

I get others of my tubes from a local company (whose owner has been at the manufacturer overseas), and the manufacturer is well known.

Are you trying to save money, or trying to find a tube that sounds different from the rest?
What brands of EL34 have you tried?
 
#13
Well I have a matched quad I got for free and I was just curious on what sets this tube apart from the rest of the EL34's on the market today. In reading the data sheet they claim its in fact a beam power tube and its capable of 30 watt plate dissipation. The extra plate dissipation could be handy for some applications. Also the less screen current (common for beam tubes) is attractive for guitar amps being over driven, I.e. they might not melt.
 
#14
Re post #8 it was actually Philips that had the patents on power pentodes and EMI passed along the rights for the beam power tetrode to RCA as they had the resources to develop it thus getting around the Philips patent; the 6L6 was the end result.

https://en.wikipedia.org/wiki/Pentode

https://en.wikipedia.org/wiki/Beam_tetrode

My vintage Sylvania 11th ed manual refers to the 6BQ5 as a "Beam Power Pentode" and has G1, G2 and G3 as you would expect. (It's not listed in my 10th ed copyright 1955)

RCA in RC-24 calls the 6BQ5 a power pentode, and again has G1, G2, G3..

GE in Essential Characteristics (1963) refers to it as a beam power tube but again shows G1, G2, G3..

Philco Handbook of Tubes and Semiconductors does not reference the 6BQ5 at all, but lists the 6BD5 (a type I use in series pass regulator service) as a beam pentode.

Certainly little uniformity in nomenclature.

Interestingly the 6BQ5 Jedec registration (list # 1686) is to Rogers of Canada as a proxy for Philips in North America. Date of registration is July 1956 so prior to that there were no tubes sold under 6BQ5.

I have never seen a 6BQ5 that was anything but a pentode. (I must have seen hundreds by now if not more)
 
Status
Not open for further replies.
Top Bottom