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EL91 Max ratings ? help

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If you wind up the juice too much on such tiny valves they will just give up and die.

I posted a whole load of stuff about the 6V6 family yesterday, the upshot being, you can get away abusing the daylights out of the octal ones.

Most of the smaller clones were made for car radios and other wimpy budget devices, and weren't supposed to get a caning anyhow.
It was all "marketing!"

Horses for courses!
 
Anyone that somehow believes they're onto a winner with a British 7pin output valve, must be crazy.
These were designed for el-cheapo budget table top radios.

It was typical of the Dutch and British (phillips-mullard combo) to be selling this sort of junk to joe-public, then 50yrs later it all gets fashionable again as that age group come up to retirement, - (just like the old 60s British sports cars are to the same white haired generation also).

You need to be very conservative with ratings for anything to stand any chance of working how it should.

Eg.
6L6 max 360V
6V6 max 295V
EL84 250V
EL34 400V (800V was always a joke, it might work for a few hrs before melting!)

And EL91/95 220V

A lot of the myths about Mullard being a quality manufacturer need to be debunked.
I still can't get it how people ever imagine the EL84 or EL34 as a quality product.
 
mullered said:
Anyone that somehow believes they're onto a winner with a British 7pin output valve, must be crazy.
These were designed for el-cheapo budget table top radios.
EL91 = 6AM5 - I suspect it was actually an American design. They used miniature valves before Europe.

A lot of the myths about Mullard being a quality manufacturer need to be debunked.
Then debunk them. We are waiting for evidence. Should we order popcorn?

I still can't get it how people ever imagine the EL84 or EL34 as a quality product.
That could be construed in two ways:
1. a statement of your inability to "get it"
2. a statement claiming poor quality for EL84 and EL34
If the EL84 was so poor a design, why did the Russians copy it?
Why did RFT in East Germany produce so many EL34, still highly regarded as NOS?
 
EL91 by all accounts was European Philips stuff, - a scaled down 6V6 intended for car radios and the like.
I don't think the Americans were ever keen on those silly little 7 pin, 6.3v things with pins that were easy to wreck, and had bad contacts.

I think the USA preferred octal & noval right up to the end, while the Germans made their own high quality sockets.
Look at the quality of a German radio from Grundig or the like, compared with the rubbish from the UK at the time.

Isn't anecdotal evidence from people who actually worked at the factory good enough?
The epic EL34 failures at Mullard, were a standing joke amongst their own workforce at the time.

Also, you may notice the Russians as usual copied only western consumer goods, such as the Leica camera (Zorki), Fiat (LADA), the Volga (based on an old GM design).
Their consumer end stuff were soviet jokes of the time it was so bad, only Honnecker's Germany DDR made worse stuff.

The rest such as the fridges, radios, cars of any quality, were almost invariably made elsewhere in the USSR (Eg.Riga Latvia) or (Czech) Skoda.

If you are talking about proper Russian valves with no western equivalents, they invariably were specially made and ordered for the military.
Don't you remember those times or anything?
 
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mullered said:
EL91 by all accounts was European Philips stuff, - a scaled down 6V6 intended for car radios and the like.
Evidence? The EL91 is nothing like a 6V6. The 7-pin '6V6' is the EL90/6AQ5.

I don't think the Americans were ever keen on those silly little 7 pin, 6.3v things with pins that were easy to wreck, and had bad contacts.
By all accounts it was the Americans who invented those silly little 7 pin 6.3V things which we now know as B7G or miniature. Do you have evidence to the contrary?

I think the USA preferred octal & noval right up to the end, while the Germans made their own high quality sockets.
No, Americans usually preferred B7G - it was Europe who prefered noval (9-pin miniature).

Isn't anecdotal evidence from people who actually worked at the factory good enough?
The epic EL34 failures at Mullard, were a standing joke amongst their own workforce at the time.
Evidence? Even just a link to an anecdote?

Also, you may notice the Russians as usual copied only western consumer goods, such as the Leica camera (Zorki), Fiat (LADA), the Volga (based on an old GM design).
I understand that there were Russian clones of Western mini-computers such as the PDP-11 - clearly not just consumer goods, but industrial/military too. There was even the famous Russian clone of Concorde; it was reported that the plans stolen/leaked to them contained deliberate errors so the clone did not fly very well.

If you are talking about proper Russian valves with no western equivalents, they invariably were specially made and ordered for the military.
No, I was speaking of what we now know as the 6P14P - which is virtually a clone of the EL84. Many Russian small-signal valves were surprisingly similar to Western designs.

Don't you remember those times or anything?
I was alive during the Cold War. So what?

So far, your assertions in areas where I have some knowledge have turned out to be false. Could you at least try to back up your assertions in other areas with some evidence - or should I assume that they are false too?
 
The Americans copied European valves, the Europeans copied American valves. The Russians copied both. What is the big deal here ??

However the Russians both produced some of the best quality valves and some outstanding designs of their own.

Shoog
 
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Totally agree with the last poster, and then of course there was all this patent nonsense for decades.

Don't forget Philips is Dutch, and they are not known for being generous, which is how they made fortunes out of yet another dire and dreadful product,- the compact cassette.
In any large scale industrial production facility turning out over 1 000 000 valves a week there are going to be economies of scale, and efforts to bring the quality down to a level which is JUST passable for the punter.
That is capitalism, which of course the Russians with their centrally planned economy don't have to this day.

The sheer quantity of raw material dictates these economies of scale, and lets not forget the UK had dire industrial relations, riven through with class issues, throughout the 50s right into the nightmare late 70s.
(I grew up there!)

A member of my family worked at Mitcham before he went off to work in nuclear particle accelerators.
As kids we were surrounded by buckshee bits of Mullard stuff, and could more or less help ourselves to those (POS) EL34s.

We had lots of fun making all kinds of projects and the 6V6 based home made record player, we thought sounded great, -but it WAS mono after all.

Philips were an arrogant predatorial bunch, so they refused to admit anyone else made better stuff and more or less denied the existence of the KT stuff from "shock horror" M-O-V, a direct competitor.
(A KT88 is a hard valve to melt, an EL34 is a kamikaze valve as soon as you get the G2 close to the limit)

None of this should come as any sort of suprise to a seasoned British industrial archeologist.

The coal mines were run on feudal lines, the motor & motorcycle industry slid into an abyss, the shipyards went on strike until they hit the rocks, the aviation industry struggled to survive the shock of the cancellation of the TSR2, and the railways were being closed, and the entire machine tools industry was using worn out stuff from pre-world war 1.
One of them British TIMKEN was still using that stuff until the factory caught fire in the 90s and was finally close!

The whole idea that an industry in terminal decline like Mullard was right through the 60s and 70s, should be motivated to produce top class products for crap ,*** produced TV sets, while soon competing like the rest of industry with much better made japanese stuff is a nonsense.

Of course quality control is gonna go down the pan.
I mentioned something like these a few days about "every decade sees a pinnacle of technology".
The radio valve's pinnacle in the EEC as it was then was about 1955-1971.

Today you can do repeatability with CAD, CNC & robotics, but sure as anything the quantities are not there to be able to reject a batch of 50 000 valves that fails QC in a week.
It AIN'T gonna happen especially in China or the far east!

Mullard keeled over well before the last sell by date in 1983-4, which was like the British motor industry, living in the past and reflecting on past "glories", propagating myths to all and sundry.

It makes me laugh when people claim they detect the sonic differences between what is simply PRODUCTION SPREAD, in a what is an unacceptably wide tolerance product, something you would never ever accept in something mission critical.

Look what happened to HUBBLE when they got that wrong!

You cite the Russians copying concorde.
You don't really have a clue there.
Even in aviation they got used to living on the ragged edge to try prove something, as the world headed towards another pinnacle of technology (civilian supersonic air transport).

The TU144 although loosely based on Concorde was a totally different plane with a totally unrelated internal construction, the wrong engines and landing gear, which of course is why it was a total failure, nothing to do with the popular myths.
The current TU160 is an awesome plane based on some of the very best USSR technology (1981/7, modernised in Nov 2014). It's the world's fastest nuclear bomber.

How do you explain that?
They copied it off the British or Americans?
What about Buran?
Copied from the USA too?

In fact if you carry on repeating popular myths, there's little point in continuing.
You are not on the same planet.

Read some of this:-
This is much more like the Mitcham Mullard my dad described, complete with the melting EL34s in the PA that wouldn't last more than a week...

Fascinating stuff.

Mullard valves questions - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum
Mullard valve answers - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum
How many valves did Mullard ever make? - UK Vintage Radio Repair and Restoration Discussion Forum
 
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mullered said:
That is capitalism, which of course the Russians with their centrally planned economy don't have to this day.
You need to read the forum rules about acceptable topics for discussion.

Philips were an arrogant predatorial bunch, so they refused to admit anyone else made better stuff and more or less denied the existence of the KT stuff from "shock horror" M-O-V, a direct competitor.
In a free market very few firms will admit that a rival has a better product. This is not just a matter of politics or economics but human nature. I suspect that even in a controlled economy (whatever the political system) you won't find the manager of Tractor Factory No.1 admitting that Tractor Factory No.2 has better quality/productivity/energy use.

The cited threads from the UK forum (of which I am a member) don't seem to add anything useful to this discussion.
 
You need to read the forum rules about acceptable topics for discussion.
What is unacceptable about discussing about Russian, and British, (Dutch) production methods and ethics.
Do you want to censor such remarks?

I know both sides of the coin quite well, - much better than you might ever imagine.
:shhh:

You are also way wrong on ex-soviet style economies.
In a centrally planned economy and/or one that relies on large state intervention there is not even remotely a chance of one factory disparaging another's...
They even have to use common components for each others products.

(Eg, the Belarus tractor which is an excellent tool even admitted in the west, and look at the development of Chinese industry, or the development of the Alsthom TGV or multi national industries.).

That unique privilege is reserved for the western capitalist system,- generates equally astonishing levels of waste, by nearly always choosing inferior technologies sold only on superior marketing,- then shortsightedly laying waste, crashing, burning & shuttering whole sections of industry, which it then turns out to need as part of a crucial infrastructure sector only a decade later.

(Look at the UK nuclear power generation industry as a perfect example of this.)
 
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What is unacceptable about discussing about Russian, and British, (Dutch) production methods and ethics.
Do you want to censor such remarks?

I know both sides of the coin quite well, - much better than you might ever imagine.
:shhh:
If you want to discuss this then please start a new thread because its firmly off topic and not helping the poster answer his specific question.

Shoog
 
The answer was given.
The EL91 is not suitable for anything more than table top consumer radios of the 1970s, and neither is the EL95.
I made a P-P amp with them some 30yrs ago using all the right bits.
They huff and huff 'n puff, get really hot and don't do much of use at all.
It was real rubbish.

I heard people had more success using a tiny pencil tube the 5902 even for a guitar amp.
I wonder what you would get if you wired 2 quad of them in parallel push pull?

I'll bet it would blow the socks off a 6V6 at only 150V.

DSCN2280b.JPG


That takes a tiny fraction of the space, costs peanuts, doesn't need a dedicated socket, runs down under 100V and you can abuse the living daylights out of them!
 
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One thing interesting noticed on the Mullard data curves for the EL91.

The flattened out (ramp) section of the gm curve moves to higher current with higher Vg2. Useful to know, assuming it applies to other tubes. Rarely see gm curves for output tubes, and very rare to see the gm plotted for different Vg2.

pages C6, C7 (you have to use the Ia curves at the same grid1 voltage located on the gm curve)

http://frank.pocnet.net/sheets/129/e/EL91.pdf
 
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I think this is all you will ever need to know.

The problem with these EL9x valves is the wimpy little Ia 20m/a max + the fact you have to drive it with 38v pk-pk (!) a-a is 15k and all you get in the end p-p is a wimpy little 5W!
The heater is a weedy little 0.2A, if that's not immediately making you suspicious...
That's a lot of wire to wind in a transformer which will be far from optimal, and nobody makes +you will have a gross mismatch with headphones.

It's not so cheap, people on ebay are trying to get an outrageous 13EURO with cryo treatment whatever difference that is supposed to make!
If that's not one of the worst audio valves in the world I don't know what is.

By comparison:-
The tiny little crayon 5902 conducts 50% more current, (but that's a mil rating so you can get 50m/a quite easy). The heater current is more than TWICE the EL91, which means it has a serious rated cathode emission

You can drop the whole amplifier on the floor from 3m up and it will still carry on working.(it's rated to 450G impact loads)...and you can get 10 for 30 USD!

You'll get the same power as the EL91 with something the size of the cap of a biro pen and it takes HALF the drive voltage to get the same output into 3>6K, even wired as a triode.

The guy who makes the amps above contacted me a few weeks ago, because the transformers are a pig to wind for good bass reponse for such low currents.
This is what he said, VERY FAIR, and would apply for the EL91 too!

The transformers I designed for the 5902 is 6.6k and was designed
primarily for a guitar amp. It has a frequency range that basically covers
the range of a guitar and I doubt it would work very well for 30 a 20khz
range.

Low E note on a guitar is 80 HZ and my transformers were designed
around that criteria on that end of the low scale. Most of the off the
shelf stuff like the Hammond transformers only go down to about 100 HZ. On
the high end of the scale mine go to about 10k, which is also more than
enough for a guitar amp but not the 20k you are looking for. I also had
physical size restraints for my design so it would fit on the circuit
board.


Clipping, saturation, compression and sustain
are design characteristics that make for a good guitar amp but not so much
for an amp that faithfully reproduces music.

One of the features of
transformers is that to get a good bass response you need more inductance
in the windings which means more turns of wire and a core that works well
for the transfer of energy. It is really hard to make a very small tranny
with a lot of turns without using some smaller gauge wire.

My transformers
were designed this way but the wire used was so small that a the winding
machines at hxxxxx were not set up to use that small of a gauge wire.
They had to be wound by hand. I was shocked when Pxx at Hxxxx told me
they wind mine by hand.
Mine also only have a 8 ohm secondary for an 8 ohm
speaker.
I'll bet wired in pairs like these, you can get 100m/a into 3k a-a load at 150V which is an easy 10W, a lot more if you want to go mad!
usa_ge_5902a.jpg

Why bother? I would drop an EL91 in the first dustbin, if I ever spotted one again.
 
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