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Author Topic: VF14 measurements vs substitutes  (Read 6939 times)

granger.frederic

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VF14 measurements vs substitutes
« on: February 01, 2014, 04:01:28 am »

Hello everybody,
i know this subject has been discussed many times but did you see this article ?

http://www.moxtone.com/mU47_U47_part3.html

i think that this kind of method is more reliable than purely subjective feelings...
what's your opinion ?
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soapfoot

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Re: VF14 measurements vs substitutes
« Reply #1 on: February 01, 2014, 08:00:33 am »

i think that this kind of method is more reliable than purely subjective feelings...
what's your opinion ?

I disagree with this position! At least I do when the exact goal is to select a device that creates a "good subjective feeling!" Analogously, I would not let my opinion be swayed by a test designed to "prove" that a given banana tasted better than another variety. To me, the ultimate and most elegant and reliable test would be to simply taste both and choose my favorite. For our interests of choosing which device is best to listen to, I find that the most reliable method of test is to actually listen to it.

Ultimately, such empirical tests give us an indisputable baseline of numbers and figures to argue about, and that's interesting. But as my dad used to say, "figures lie and liars figure."

Applying the scientific method to subjective listening matters quickly turns cumbersome, inelegant, and inconclusive because the number of variables to isolate and measure becomes impracticably large-- In order for such a test to be definitive, we have to be certain that every relevant variable was isolated, tested and accounted for. It's hard to even find consensus on which known variables matter, not to mention any yet-unanticipated or yet-unmeasurable variables worth considering. When thinking of all the possible variables in a device as complex as a vacuum tube, tests like the one to which you linked begin to look very crude indeed, and may not "prove" anything-- particularly when human perception is such a widely variable moving target.

Appealing sound-- like appealing taste and appealing appearance-- is a sensory/sensual experience. When we attempt to reduce it solely to a debate between sets of empirically collected data, something inevitably gets lost in translation. This is why we don't select art, wine, or lovers using the scientific method!
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Jim Williams

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Re: VF14 measurements vs substitutes
« Reply #2 on: February 01, 2014, 11:05:53 am »

"Trust, but verify"  ~ Ronald Reagan
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klaus

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Re: VF14 measurements vs substitutes
« Reply #3 on: February 01, 2014, 01:20:11 pm »

I only glanced at the comparison treatise. (Can someone please make an argument why I should read every damn graph and exposé about microphones and take it seriously, just because it's on the interwebs?)

The testing methodology is faulty, even on a cursory read: It is claimed that in U47-like applications, the EF14 usually is heated with a max of 5VDC. That is not my understanding and my experience. It is usually heated with 6.3VDC. Grossly underheating any tube has its audible artifacts.

If you argue that, as basis of comparison, underheating a specific tube with significant differences in construction to its comparator tube should be the basis of comparison, you've lost me.

Garbage in = Garbage out
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Klaus Heyne
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moamps

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Re: VF14 measurements vs substitutes
« Reply #4 on: February 01, 2014, 02:13:33 pm »

Klaus, as you said, you only glanced at the article so please allow me to correct you on some points.

For all tubes in the test sample, you have their output characteristics for several heating voltages, as can be seen in the graphs. The heating voltage of 6V is also given for the EF14. The measurements show that the output characteristics of the VF14 for the heating voltage of 35V are the same as the output characteristics of the EF14 when heated with slightly under 5V. What is claimed is that in order to get the same output characteristics as in the normally underheated VF14, the EF14 should be also underheated, with 5V. What is also stated (in 2 places) in the article is that the underheated EF14 is usually prone to microphonics. This is it, no more and no less.

The idea of substituting the VF14 with the EF14 underheated with 5V has been discussed by others on this forum, such as in this thread: http://repforums.prosoundweb.com/index.php?topic=5513.0 . You may be familiar with the implementation proposed by forum member Oliver Archut: http://www.tab-funkenwerk.com/id68.html

To sum things up, the article deals with the measurements of steel tubes and their output characteristics for different heating voltages and how their electrical properties compare with the VF14. It is a strictly technical article. Raw data, if you will. The testing methodology is perfectly fine for the purposes stated in the article.

Milan



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granger.frederic

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Re: VF14 measurements vs substitutes
« Reply #5 on: February 02, 2014, 10:40:50 am »

Thanks Milan,

i tired to read ( from only few "authorized" people ) that this tube, or capsule, or caps ... doesn't sound good...it's too subjective.

we must do some measurements and after we can debate ...
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soapfoot

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Re: VF14 measurements vs substitutes
« Reply #6 on: February 02, 2014, 11:19:52 am »

or we can all listen, and then debate.

Of course it's 'subjective.'  It's art we're talking about capturing/creating. Microphone choice often straddles that region between 'capture' and 'sound design.'

Why is subjectivity a bad thing?
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granger.frederic

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Re: VF14 measurements vs substitutes
« Reply #7 on: February 02, 2014, 03:07:22 pm »

subjectivity is not a bad or good thing...
we're talking about rare tube substitution in order to have the closest sound of the original.
here, someone has done some measurement with VF14.
he (or we) could do the same with AC701.
I think that measurements/graph with tubes are very reliable.
A tube doesn't have its own sound.
It's the way it reacts with the components around.
If you find two different tubes with the same datasheet/graph, in the same application, the chances that they sound close are good.
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klaus

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Re: VF14 measurements vs substitutes
« Reply #8 on: February 03, 2014, 12:20:56 am »

A tube doesn't have its own sound.
That statement, to put it politely, is a hypothesis which would need to be backed up to be credible, or it would need at least to come from someone with credibility in the field of microphone development, audio analysis and perception, or deep musical background.

My experience has shown that every tube employed as impedance converter in a condenser microphone has its own sound, even if used in the same application, same microphone, same everything. You substitute one EF86 Phillips with another one in a U67 or Brauner KHE, for example, and you will notice a different timbre, every time.

I used the variance in tube performance/timbre to better match and fine tune KHEs for pre-order clients before they would be sent off.
Try to graph THAT!

I have found it unproductive to argue the same old point of view, that not everything we hear can be expressed in an objective quantification. We are not there yet with analytics (and computing power seems to be concentrated these days more on tasks like buying behavior analytics, rather than esoteric audio queries which make no money for anyone).
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Klaus Heyne
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granger.frederic

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Re: VF14 measurements vs substitutes
« Reply #9 on: February 03, 2014, 08:36:02 am »

Dear Klaus,
With respect, off course you have different sound with different tubes even in the same brand and even with the same reference.
only matched pair have the same sound.
their graphs are different and the way it reacts with the component around is different.
Tubes are hand made, so it's nearly impossible to have perfectly matched tubes, in a sample of 10 for example(i've read somewhere that Nagra reject 990 tubes of 1000).And that's why they sound different.
An electron field in a pair of VF14 doesn't have "a sound" but it can be different depending how the inner structure/components are built.it's not something "esoteric", if it doesn't sound the same, you can measure why.(if you know what you have to measure)

We all know your position about rare tube replacement (see my previous post about my M367), but i think we can debate:i've seen last week, on EBay, a VF14 at 1200 euros....with no return possible, no comment...(did you said no money ????)
Obviously, the time has come to find an alternative !
I just prefer experiment/make efforts/do some measurements/debate, than saying it's impossible.(Andreas Grosser, for example, has done that and now sells some alternatives...).Period.
Sorry if it's impossible here , i'll find another forum.
Regards
Fred
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klaus

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Re: VF14 measurements vs substitutes
« Reply #10 on: February 03, 2014, 01:31:13 pm »

By all means, please find another forum if your main goal is that others agree with you.

You make an absolute statement ("a tube doesn't have its own sound"). I challenge that statement. Then you respond over a whole paragraph that you agree with me ("off course you have different sound with different tubes even in the same brand and even with the same reference") and then... I am getting confused.

I will respond in detail in a day or two to the link you posted. In the meantime, please remember that, through I don't know a single audio professional with access to genuine VF14 who would voluntarily choose a substitute, I warmly invite reports from users of alternatives to expensive, obsolete tubes like Telefunken's VF14.

Users, not posters of unexamined claims or graphs. I am highly skeptical of supposed proof of sound similarities of tubes, as we all know that most who use graphs in audio use them to bend reality towards a specific outcome, rather than find truth by starting out from a position of neutrality, and the few who actually have experience with the subject matter, are not the target audience.

I recommend to you "Proofiness", a book that details the easy entry of "objective" numbers, graphs and statistics into our brain's centers of credulity. 
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Klaus Heyne
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granger.frederic

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Re: VF14 measurements vs substitutes
« Reply #11 on: February 03, 2014, 02:00:41 pm »

Dear Klaus,
first, i don't what to convince you or anyone.
i wanted some opinions, i now have yours.
you're skeptical, fine, but i'm not alone in quest of a vf14 substitute : see the multitude of post in various forums including this one, and see the famous mic techs like Grosser/Wagner, see the famous manufacturers like Telefunken/Flea, etc,etc,etc ....
i don't voluntary choose a substitution, it's exactly the opposite.But i/we need one or multiple alternatives, even if it upsets you .
I just don't what to spend a week of studio work with a supposed new old stock rare tube which doesn't work for mic application (like i did before...)
i just don't want to be "le dindon de la farce" anymore.
Please read my posts again, and you'll understand what i mean by "no sound"
(the quotes are important), i tried to be didactic (with examples) but perhaps it was too abstract...
Thanks at all the people who post here
Good luck
Kindest Regards
Fred
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klaus

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Re: VF14 measurements vs substitutes
« Reply #12 on: February 03, 2014, 10:04:33 pm »

The site the OP refers to (http://www.moxtone.com/mU47_U47_part3.html), claims, in so many words and graphs, that there is no measurable difference in performance between the VF14 tube and supposedly similar tubes, all of which require a separate heating supply.

The larger context of this article, unfortunately, is not enlightenment but the promotion of the web host's product, a dual-output voltage power supply he manufactures ("Moxtone")*, which can power aftermarket U47 copies with separate heater supply (the product does not work with the VF14, the original U47 tube).

The scientific-appearing tests are meant to show that the VF14's unique characteristics are not unique, after all, thus making other tubes, which the product is designed for, acceptable alternatives.

All of that is done by conditioning the reader with scientific-sounding material:

"Hopefully, you will find the data presented in this article a sufficiently valuable contribution to the relatively scarce body of knowledge on the VF14 and a significant help in designing microphones, particularly in understanding and evaluating different options once the VF14 wears out and fails, which it most certainly will."(italics and bold added)

The article uses questionable methodology in its test arrangement and execution. I already mentioned one in a previous response- the fallacy of lowering the heater voltage of the EF14, which does not take kindly, loses noise floor, and clogs up its cathode with time; is not peer-reviewed, and lacks objective, scientific approach appropriate to discover new information.

Its further discussion, therefore, has no merit for this forum, and the usual caution applies: if at first you don't understand the reason why something is pitched to you, just follow the money.

Thread closed (violation of forum Ground Rules), but kept up for benefit of the reader, as a slick example to study how quasi-science is put into service to peddling a product.



* I have no opinion about the product's quality, or lack of, to power U47 copies
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Klaus Heyne
German Masterworks®
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