Measured VF14 characteristic

[o3misha]

Sergio, There is nothing to save!  Andreas saved me from a huge number of errors that occurred after contact with Oliver and Klaus,-they told that any working  VF14  is better tube for U47 than other tubes. I'm sure today,- it is  not true! I personally made sure that just is not enough to use tables and directories to configure the operating mode in the microphone. Moreover, even set up your microphone with a good lamp is impossible with only basic facts and standard scheme. A simple example: nuvistor. Many experts have rejected this lamp. Why? My answer: they are not versed device lamp technology.
    About EF12 lamp :  Often requires correction resistors and anode supply to achieve the best result. Taking Andreas scheme still need his experience to properly set up the lamp. Can achieve much better results from the EF12. And the sound of the microphone will never be thin. It is my deep conviction, because I heard the sound changes from the simple replacement of a pair of resistors.
    About Vf14er and VF14ef : why argue about it? Try,-and then tell us about your feelings!
    About varnish and acryl:
I personally have been visiting Mr. Thiersch in his lab and Andreas - they  know everything about Neumann capsules and possible problems with HighZ parts in U47 head. I would say that they really helped me to solve all my problems with microphones and continue to help everyone who wants to find help. Period.

 

[granger.frederic]

dear misha

when you talk about EF14 : "It made ​​me participate in a topic that others avoid my mistakes, waste their time with that tube, which was not designed for audio( not granger.frederic, of course)"

could you agree that your mistakes may not be mistakes for others ?

and why are are stating that ef14 was not design for audio ?

this kind of certainties makes me feel that you have a lack of basics about electronic design and tubes.Maybe i'm wrong...

VF14/EF14/UF14 were RF/IF-Stage pentodes with small structural differences and different heater.We can use them, off course, in a BF design as well.

EF13 is another animal because of its automatic variable mu.
EF12 is a very good tube used in many mics and preamps but for me and a lot of DIY'ers , it sounds too HIFI/THIN in a U47.

BUT the fact is that i'm not completely satisfied (see previous posts) with an EF14 in a U47 , thus i debate in this topic.

Nuvistors are state of art tubes and often underrated, i'll report here asap after some tests.

Vf14ER and V14EF are sold by A.Grosser, only for Neumann U47 owners, thus in a DIY forum ....

there are more solutions, more tubes to test , more designs possible, see Max IOAudio with 408a in parallel ...
i've test that also. It works very very well, but this design has more noise and i've found it a little weak on transients.(probably due to the doubled inter electrode capacitance)

 

[Melodeath00]

I agree with micaddict that it is sad o3misha deleted his posts.

granger - you should try an EF800 or EF802, as well. I'd love to hear your thoughts.
It uses a separate heater. I did not design my PSU, so I do not know if the heater supply is "perfectly stiff" or especially quiet, but I can tell you my mic sounds good and quiet, as well. I have no original U47 to compare to, though.

 

[o3misha]

and why are are stating that ef14 was not design for audio ?

Not EF14, not VF14 were not designed for audio. Neumann choosed VF14 for U47 because this tube needs only one feeding. Thats it! It was good and comfortable decision. It can work without problem with very simple power supply. Usual reason why DIY-ers  use EF14 instead of VF14 is similar datasheet and good PR. EF14 was never used in microphones (at least in Neumann mics). I am sure, that all specialists on Neumann were very interested to replace VF14 in U47 and continue U47 production. But...

this kind of certainties makes me feel that you have a lack of basics about electronic design and tubes.Maybe i'm wrong...

EF12 .... , it sounds too HIFI/THIN in a U47.

1.There are no many DIY-ers using original or just good enough BV08s.
2. Many DIY-ers did not adjust circuit for each EF12. Standart schematics tell us only very common info. This rule is working with any tube. Neumann used VF14s tested only for noise and microphonic and did not adjusted common circuit. Thats why many U47s sounds like sh*t.

Vf14ER and V14EF are sold by A.Grosser, only for Neumann U47 owners, thus in a DIY forum ....
.

As far as I remember, you told us about your original U47n, isn't it? Thats why I told you about Andreas and his tubes.
Anyway, everyone may ask Andreas to give his VF14er for test (as far as I remember,but I don't remember details). I bought his VF14er as replacement for my U47s, but I had an option to return it after test and return my money back. Of course, I did not return the tube, - I'm happy with it.

 

[granger.frederic]

dear melodeath,

well i've tested EF800 and EF 844s in my U47n and in a Wunder CM7GT M7.this family is very musical and works very well with m7/K47 capsules imho.
However, they react differently than VF14 probably because of their really higher internal resistance .

you're right to say that there's still the 6,3v fixed bias issue/heather issue .

I'm working with a 12va Toroidal transformer , full wave rectifier, 10 000uF, then the max possible Inductor , then LM317, then RC again.It's quite stiff but still a little noisy (but usable).

Cheers

ps: Misha, could you stop ...?Or add something new please.

 

[bruno2000]

....Nuvistors are state of art tubes and often underrated, i'll report here asap after some tests.........

Thank you!  I agree.  Can't wait to see the test results.
Best,
Bruno2000

 

[Melodeath00]

dear melodeath,

well i've tested EF800 and EF 844s in my U47n and in a Wunder CM7GT M7.this family is very musical and works very well with m7/K47 capsules imho.
However, they react differently than VF14 probably because of their really higher internal resistance .

you're right to say that there's still the 6,3v fixed bias issue/heather issue .

Very interesting. Can you describe in what way they react differently? People compare EF12 and EF14 to VF14 all day, but it's rare to hear someone try to describe EF glass tubes versus VF14.

 

[granger.frederic]

Dear Melodeath,

Well, i'll try to describe my feelings with ef8XX but it's hard for me in english, because of my limited vocabulary.
First, let's talk about EF8XX in a design with fixed bias/BV8/K47 .
The ef800 has less low end due its lower inter-electrode insulation.
Then, it has less transients/high end (a sort of weakness) due to its higher output/internal impedance (in triode around 20/30K), thus there is a mismatch with the BV8 and this is for me a deal breaker.
However i think it produce a very rich and pleasing sound in the "reduced" hearing range, probably due to its harmonic distortion profile.
the EF8XX family is often used in self Bias in various preamps and are highly usable in mics : see miktek cv4 for ex.
Cheers

 

[Melodeath00]

Thanks for the reply, granger.

However, can't you alter output impedance by adjusting the anode voltage? From what I understand, at typical U47 anode voltage, and EF800 has higher output impedance, but it gets lower as you increase anode voltage.

 

[o3misha]

Thanks for the reply, granger.

However, can't you alter output impedance by adjusting the anode voltage? From what I understand, at typical U47 anode voltage, and EF800 has higher output impedance, but it gets lower as you increase anode voltage.

Or(and), adjust anode resistor  value, for example. Or to use another transformer's ratio, -why not? I've always been curious as to why no one is trying to make BV08-ish transformer on the same dimensions ,winding technology as the original BV08, but suitable for other lamp  ratio and to get best results? Its reasonble:  another tube- suitable B08-ish x-former, isn't it?

 

[granger.frederic]

adjust anode resistor is the same than increase anode voltage: ohm's law.
it helps but i'm not sure it will decrease to 8/10k even at 100v.
in the same time it will change the gain and noise too, and things will become more and more complicated...

oh, i remember a trial with a EF42.It was musically interesting, but the noise floor was too high and it was ultra microphonic.

 

[o3misha]

adjust anode resistor is the same than increase anode voltage: ohm's law.
.

It's not the same thing. Increasing anode feeding  you must also control the bias of the lamp to make a difference for current and reduce resistance .  Its good, but not enough. It has little effect on the frequency and dynamic of the microphone. Changing the load resistor , say at a lower value - changing interaction between lamp and the transformer , which leads to changes in the dynamics of the amplifier, as tube is working "more free". This is particularly noticeable at dynamic of low frequencies. That is one of the trick of adjusting the circuit...

 

[granger.frederic]

sorry misha but could you rephrase that ?

do you mean increasing the "cathode" resistor ?

i'm very curious, could you explain also the "working free" trick ?

to make things simple, if you decrease R anode then you increase V anode and you decrease Ri.

 

[granger.frederic]

dear Misha,

i'll try to tell that in a more simple way.
In unbypassed fixed bias, if you decrease R anode, you increase the anode voltage.You don't loose so much gain, only 2 or 3 db if you stay between 50k and 100k.However, you decrease by a factor of 2 the Ri, with 50K, but it's often still too much for a BV8 and a tube like 12AY7 or EF800.
I think that the operating point of a tube is not so much critical sonically, and there's room to make it easily work.
cheers

ps: here's a good beginner's calculator for a triode: http://amps.zugster.net/tools/triode-calculator.

 

[granger.frederic]

Dear misha

Please stop that paranoid attitude
I'm not upset at all
My previous post was very polite
I'm sad that you've misundestood it
It was addressed to all the readers , the calculator link also.
Please PM me if want to do a private discussion


The 12ay7 was an example for diý'ers/readers who are not familiar with tubes
Increasing anode feeding is probably increasing B+, i suppose, but you will change the capsule polarisation, thus you'll need to change everything, even the Psu.the safiest way to increase Va is to decrease Ra.

The public enemy in a mic is noise floor, increasing B+ or Va,or reducing Ra, is imho not the most evident method.That's why Neuman and many MF, use low Va in their tube mics.

Concerning another transformer, i think it's off topic, we're talking about VF14 substitution/measurements in a u47 design.
Cheers

 

[granger.frederic]

Oh my gosh,  I think i'll leave this topic ....

Attention Please, to all DIY'ers !!!

DO NOT put more than 60/65V on your capsules.

Even if it will works at the beginning, it will change the membrane tension in the long term.Thus it will damage all of the M7/K47/K49/K67/K87 and especially CK12 capsule type.(All large diaphragm capsule type).An electric arc or arc discharge, could eventually destroy the membrane also, with a too high voltage.

Misha, please stop modify your posts after a long period.
it's more fair to post again.

To answer you , yes you can put higher voltage if the diaphragm has been tensioned for, and it's not the case for most.

 

[o3misha]

[quote author=clink=topic=53620.msg708548#msg708548 date=1394268330]


Misha, please stop modify your posts after a long period.
it's more fair to post again.

To answer you , yes you can put higher voltage if the diaphragm has been tensioned for, and it's not the case for most.
[/quote]
I will do better: I will stop to answer you in the future.
What I sense to write new posts , if you rip words out of context ? I did not rewrite my posts I only corrected them after your next message that indirectly says that I'm lying to all, or saying something never tested by you. You either did not understand my messages correctly or don't want to understand. Its clear for me now.
Again : 80VDC is normal voltage for most of modern best M7 capsules : Gefell, Thiersch, or modern Neumann K47 capsules. There are some modern  historical Gefell and Neumann  mics with 70-80 VDC polarization voltage of M7 and K47 capsules.
Dear Fred , could you stop answering on my messages and quote me in the future.
I gave you a tip -use nuvistor ( I regret, believe me). Moby gave you the necessary values ​​of the resistor . That's all. The following messages write me an email , please.
PS: I deleted all my answers to your provoke messages. I promise : will never answer to you again if you also stop it.

 

[granger.frederic]

Dear Misha,

You can be sure that i will not write you something, as i don't need and want to talk with you.

the difference between me and you , is that i'm open to everyone's suggestion, even from beginners, not only master techs like KH and AG.... :

Now please could we get back to the topic.
regards

 

[Moby]

Hey Granger it will be relly great to hear your impressions about nuvistor mod I provided here. I modify several vintage U47's that way and guys were more than happy. Just to add one of them is owner of 4 U47, two with original, working vf14m's .

 

[granger.frederic]

Dear Moby,

i'm very curious about your mod also, and it's on the way.I've received a bunch of 13CW4 NIB NOS.They seems to be in perfect shape.
I need to mod the Psu as well, to revert the mic into a conventional U47 schematic.
As the mic now needs around 55mA, i need to calculate the RC rail in the PSU as well.I don't want to regulate it.
I'm in holidays for a week ,i think i'll do that when i'll be back.
I can't wait too, but i assure you that i'll report back here with a very detailed post asap.
Thanks again for the trick

Kindest regards
Fred

PS: is there anyone here who is familiar with Germanium transistors into U47 type microphones ?