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Author Topic: EF804S vs 12AX7A Noise  (Read 18940 times)

Radd 47

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EF804S vs 12AX7A Noise
« on: January 11, 2005, 06:20:27 PM »

Oliver, how does the EF804S noise compare to a good 12AX7A?
I think a preamp made with the 804 would be much more quiet maybe?

I know that the 804 is a pentode and the AX is triode, so kind of like comparing apples and oranges...

Thanks for all you answers by the way.
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Oliver Archut

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Re: EF804S vs 12AX7A Noise
« Reply #1 on: January 12, 2005, 12:49:46 AM »

Hello Radd47,

there is no standard answer in the short form, because over the years there have been more that 1200 different reincarnations of the ECC83 family of tubes; if we exclude the current (since the western manufacture seized production) "wana be" 12AX7s production, we still end up with over 1000 different answers.

Since its introduction around end of WWII the 12AX7 changed noise and microphonic specs several times, a consumer electronic based all around double triode with a theoretical gain of 100, easy to produce and still so hard to find a good one...
Some of the 12AX7 tubes over the years had incredible test specs in reference to low noise and microphonics, but just sounded horrible, others sound incredible but quite the noisy bottle....

On the other hand the EF804S ; from the beginning a special quality type of tube with high profile applications in mind, such a tape machines or studio quality audio equipment.
Please check out for more detailed info
http://www.tab-funkenwerk.com/Tubes%20and%20use.html.

If we can settle just to compare the Telefunken ECC83 complex (flat, ribbed and ECC803s) vs. the EF804(s) I will give it a shoot tomorrow... Please let me know...

Best regards,
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Oliver Archut
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We are so advanced, that we can develop technology that can determine how much damage the earth has taken from the development of that technology.

Radd 47

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Re: EF804S vs 12AX7A Noise
« Reply #2 on: January 12, 2005, 01:41:29 AM »

If we can settle just to compare the Telefunken ECC83 complex (flat, ribbed and ECC803s) vs. the EF804(s) I will give it a shoot tomorrow... Please let me know...


That would be great! Tele ECC83 very low in distortion.
Thanks!
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Level

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Re: EF804S vs 12AX7A Noise
« Reply #3 on: January 12, 2005, 02:30:27 AM »

I like to see investigated the use of the 6H30P tube for mic pre amp purposes. I use the tube 5963 (de. of 12AU7)

Quote:

Oliver, how does the EF804S noise compare to a good 12AX7A?
I think a preamp made with the 804 would be much more quiet maybe?

I know that the 804 is a pentode and the AX is triode, so kind of like comparing apples and oranges...

Thanks for all you answers by the way.



Tube build quality (better) means less microphonics with the tube. A Pentode can be used in triode configuration actually.
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dcollins

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Re: EF804S vs 12AX7A Noise
« Reply #4 on: January 12, 2005, 03:42:00 AM »

Level wrote on Tue, 11 January 2005 23:30



I like to see investigated the use of the 6H30P tube for mic pre amp purposes.



Isn't that tube better suited to output stages, than high gain preamps?  

Quote:


I use the tube 5963 (de. of 12AU7)



Is it linear?

If you don't need all the gain of a 12AX7A, the GE 5751WA is a good replacement, imo.

DC

Level

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Re: EF804S vs 12AX7A Noise
« Reply #5 on: January 12, 2005, 04:50:50 AM »

Me

I like to see investigated the use of the 6H30P tube for mic pre amp purposes.



DC
Isn't that tube better suited to output stages, than high gain preamps?


Not necessarly. The 6h30P and 6h30pi is so low noise, you can design a circuit around it for appilactions that are beyond your wildest imagination or mine. Gain and sheilding for Micro levels.

You want output, look to the 6C33C

DC

Is it Linear?

Depends on the circuit, it is a variant of a 12AU7 but has a slightly higher MU and you can actually plug it into a AX circuit and it "heaves" some good things (dependent plate/V and amperage draw of the circuit).

Actually, depending on vintage, some 5963's are equal or even not as equal as the AU7.

Cool thing about valves, you can design around the value to obtain a goal.

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maxdimario

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Re: EF804S vs 12AX7A Noise
« Reply #6 on: January 12, 2005, 10:21:33 AM »

there is absoultely no comparison in terms of quality, noise, consistency of product (ef804s tubes came with a written warranty for every individual tube) in comparison to any 12ax7 or ecc83 or most audio tubes in general.
german special quality tubes are superior in almost every respect to any other kind of audio tube.
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Oliver Archut

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Re: EF804S vs 12AX7A Noise
« Reply #7 on: January 13, 2005, 01:29:55 AM »

As Maxdimitro pointed out the is absolutely no compression about those two type of tubes....

But let's go a bit deeper than just rumors or propaganda data still floating around from the times when the electron tubes was roaming the electronic world....

For people that do not like it to technical, do not read any further.

Here are some historic infos we have to take into account to understand the difference triode vs. pentode.

In germany the pentode, beampower tetrode and related tubes like heptodes, octodes, etc. were widely used and developed in greater numbers than the better, less noisy and microphonic triodes.

There was a reason for it, in germany everything was taxed to Kingdome come, especially around the "Kaisers" time when the electron tube was developed and started to change our lives forever; the german Kaiser taxed everything from salt to champagne, to fuel his spendy lifestyle and WWI...

One of those taxes were amid at home entertainment, more specific, the tax of a radio receiver was issued by the amount of tubes...
So nearly four month later after law passed (1915), the first tetrode (a prestage of the pentode) was developed at Siemens by Werner Schottky, that did the job of two triodes...
At about the same time GE developed their first version of the tetrode...
Siemens specificly developed the tetrode to avoid a higher tax, were GE engineers worked to get a higher gain amplifier...

The radio tax was not changed before the fall of the 3rd Reich, so all development form 1915 to 1945 was biased by this great idea of the Kaiser....
Following that Germany became the land of specialty audio pentodes, like the RE084, EF12, EF14, EF40, EF804/806, EF86, EF8010, etc. etc. For every developed triode there were about 4 pentodes, the last tube ever to be developed by Telefunken was a Pentode, the EL3010...

From the begging of the pentode age, and even to today there are hard headed people that bring arguments over arguments what sounds better triode or pentode.... (a short side info: the most wanted tube on this globe is the VF14, a pentode followed by a 300B, a triode; that should say it all)

First my compassion is not triode vs. pentode, that does not work, but an amplifier stage with the same gain powered by either one pentode or two triodes (to get the same amount of gain), in this case a EF804(S) vs. an ECC83 (a double triode in one glass container) and later an ECC803s....

To be continued...
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Oliver Archut
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Level

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Re: EF804S vs 12AX7A Noise
« Reply #8 on: January 13, 2005, 03:03:17 AM »

I love the information and history, I wait for more patiently.
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dcollins

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Re: EF804S vs 12AX7A Noise
« Reply #9 on: January 13, 2005, 05:24:00 PM »

Level wrote on Wed, 12 January 2005 01:50

Me

Not necessarly. The 6h30P and 6h30pi is so low noise, you can design a circuit around it for appilactions that are beyond your wildest imagination or mine. Gain and sheilding for Micro levels.



It might be low noise, but it's also low gain.  It's intended for output stages, no?  Isn't it related to 6922?


Quote:


You want output, look to the 6C33C



Which, Iirc, was designed for voltage regulator apps.  Imo audiofools adopted it because it looks unusual, not because of any incredible audio specs........

Quote:


Actually, depending on vintage, some 5963's are equal or even not as equal as the AU7.



That tube is usually found in flip-flop circuits!

Quote:


Cool thing about valves, you can design around the value to obtain a goal.



I don't get that statement.  How is it unique to tubes?

DC

dcollins

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Re: EF804S vs 12AX7A Noise
« Reply #10 on: January 13, 2005, 05:26:24 PM »

Oliver Archut wrote on Wed, 12 January 2005 22:29



(a short side info: the most wanted tube on this globe is the VF14, a pentode followed by a 300B, a triode; that should say it all)



If I remember my RDH4, the pentode came about due to the high internal NFB in triodes.

DC

Oliver Archut

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Re: EF804S vs 12AX7A Noise
« Reply #11 on: January 14, 2005, 11:14:48 PM »

Hello DC,

If I remember my RDH4, the pentode came about due to the high internal NFB in triodes.

I do not know what you mean with internal NFB in a triode, could you clarify that please.

If you speculating about very early tantalum, thorium, etc. cathodes types, those ones follow other physical outlines, regarding thermal noise, emission, etc. than the standard duo or triple oxide cathode...

Best regards,

Oliver
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Oliver Archut
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We are so advanced, that we can develop technology that can determine how much damage the earth has taken from the development of that technology.

dcollins

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Re: EF804S vs 12AX7A Noise
« Reply #12 on: January 17, 2005, 12:13:11 AM »

Oliver Archut wrote on Fri, 14 January 2005 20:14


I do not know what you mean with internal NFB in a triode, could you clarify that please.




This isn't the paper I was thinking of, but a start.

http://ken-gilbert.com/images/pdf/Inherent_FB_inTriodes.pdf

I think theres also a chapter in the old Radio Engineers Handbook
about this.  You can only get so much gain in a Triode (and the internal NFB is part of the high linearity).


DC

Oliver Archut

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Re: EF804S vs 12AX7A Noise
« Reply #13 on: January 18, 2005, 12:13:23 AM »

Hello DC,

thanks for the link, wasn't to sure what you were referring to, in german technical terms a process is described, in english the outcome... So the name for that phenomena is entirely different...

As an example in the english you say "radio operator" in german "funker" what translates somehow into broadcaster...

As you point out the technical limitation is given by design of the triode so in order to get a higher gain you have to get around that with at least one more grid; my point, that the reason why german tube developers tried to overcome this problem was the tax.

Before the tax was issued most laboratories worked on better reliable tubes, as soon the tax was issued they had to come up with a better solution to overcome the design limitation to get more gsain.

Telefunken played for a time with a triode that had an grid located outside the envelop, to overcome the limitation, designed by Count Arco, one of the leading figures in german tube development. It worked quite well in the laboratory, but the mass manufacturing  didn't worked out to good due to the high reject rate
Schottky's tetrode was easier to produce, even with the typical tetrode bump, a commercial triumph for Siemens...

As pointed out in an other post, Barkhausens "Handbook of the Vaccumtube" comes handy here as well, there is an entire section on the inner feedback issue...


Best regards,
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Oliver Archut
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We are so advanced, that we can develop technology that can determine how much damage the earth has taken from the development of that technology.

Oliver Archut

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Re: EF804S vs 12AX7A Noise
« Reply #14 on: January 25, 2005, 12:36:57 AM »

Lets take a closer look at the tubes..

The ECC83 is an indirectly heated double triode in Pico 9/Noval glass container, two identical systems suspended on two mica wavers locked into the glass via a zick zack cutting pattern.

Designed primary for the consumer electronic market, most home stereos, radios and in applications where high gain at low cost is required.
Build into a series of several double triodes, mostly sharing components like plate, wafers, etc. to keep construction cost low.

From the beginning the construction design microphonic vs. max. gain was compromised  with reference of easy tube construction/manufacturing. Telefunken worked very close with the American GE company and when the first samples were build in 1954 they were close to be identical to the GE ones. The first simulated life time test indicated that this design would not come close to the german required quality, so they started over and came up with the now famous smooth plate design, also used on the ECC82 with different grid and slightly larger cathode... By the way, the original blue prints indicate, smooth and grooved plate tubes are identical in material, grid winding, etc. even the opinion is different in the Audiophile world. The grooved  plate was implemented to lower the high microphonics (compared to all in production tubes it is still several times better) to reduce production rejects. Worked out quite well from 30% rejects with the flat plate, down to 14% with the grooved plate.

Even designed for the consumer market, the ECC83 quick found its way into professional/industrial application due to the right mixture of gain vs. price. Other tubes that fell into the same category than the 83, like the ECC808, E283CC, 5751, 12BZ7, etc. were mostly to expensive and to hard to get a hold of replacements in case needed.

One of the great aspect of this tube was its dual design, and even with a simple spiral filament the AC hum noise was still low enough for most professional application, especially when used in balanced pre amps so the noise would cancel itself...

However, even build in the billions it is quite hard to get a hold of good replacements, a fairly inexpensive tube in its days (approx. $0.40 for a Telefunken made one), the prices for a good Philips (Valvo/Mullard, etc) or Telefunken are quite steep today.
All in production ECC83 wana bees are sub standard for professional use (they work O.K. in guitar amps, etc.), biggest problems is the filament and cathode that keep the life time and general sound quite low; and than most of all the very high noise floor.

To be continued...
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Oliver Archut
www.tab-funkenwerk.com

We are so advanced, that we can develop technology that can determine how much damage the earth has taken from the development of that technology.
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