IOaudio Inventor of the parrallel 408a tube configuration in U47 Clone ?

melomane · Nov 12, 2014

Hi Folks, I have been watching the whole polemic regarding the U47 dual 408a tube design The "Invention" of this particular configuration for the U47 clone from IOaudio & micandmod (or poctop).
after reading this article dated from february 2009 about a year before the MK47 came out , i can draw a conlusion pretty quick that this was not Ioaudio invention as he
claimed to be is. Oliver Archut was clearly stating that saturn sound was using this configuration way before the mentionned "Invention"about a year later down the road.
I beleive the truth needs to be exposed to permits the real pionneer on this matter to be given the deserved credit.

Just my 2 cents.

see here for more details....................................................

Reply #23 on: February 13, 2009, 09:22:31 am

http://repforums.prosoundweb.com/index.php/topic,28765.15.html

Or simply this ,

Hello guys,

Saturn sound used both tubes the 407a and 408a, the 407a would have been labeled as UCC88 in the European tube code.
The 407a is 2x 20V/50mA version of the 2C51, what is in essence nothing else than a commercial grade ECC88 with a different footprint.

Running both triode haves in parallel and the filament in series gives you a replacement tube for a VF14 that will work close to the specs of an VF14.
But of all the 407a tubes I found, none of them was mic grade material, even the so called 'super-tube' Western Electric ones did not meet the simple VF14 noise specs.

The 408a is na EF95 with 20V/50mA filament, so with a dropping resistor, a direct replacement could be archived.

But here again, not the WE/Northern Electric, nor the Ericson, that were supposed to be high grade tubes, are good enough to be used in a U47.

However, the 408a/VF95s specs are pretty close in impedance as well as technical data, the head room is about 5dB less.
The tube in the pic is not Ericson, WE or RCAs because it is missing the black nickel plates.

Putting a glass tube in an metal container might be marketing, but it is still a drop-in replacement.

If someone wants a U47, buy a Neumann U47 with a VF14. If you do not have the cash nor the cash to keep the great sounding museum piece running, get a new mic.

Best regards, Flavio

granger.frederic · Nov 12, 2014

As there is no patent for this substitution, is it really important ...?

I would add to the awesome Oliver's post, that even if it's a VF14 direct replacement, two tubes in parallel are adding their noise , inter electrodes capacitance ( higher miller effect : different transient response) and other issues if they aren't perfectly paired...
i think that a single tube like the EF14/UF14/EF13/EF12 is a better substitute.

ioaudio · Nov 12, 2014

The above post from Oliver (RIP) mentions the use of a 407a dual triode tube.
I was the first using two 408a pentodes in parallel/series.
Noise comes down when using devices in parallel.

shabtek · Nov 12, 2014

I thought I had invented using the 407(based on IOaudios invention\circuit)--It worked well for me, first tube was quiet

edit: paralleling devices is not really an invention but can be a good idea.i.e. lightbulbs

granger.frederic · Nov 12, 2014

Dear Ioaudio ,
my post was not accurate enough
i had (as many users) a lot of noise issues with two 408a
the problem was not really the noise floor but the microphonic and filament noise movements (little "ding")
chances that this kind of noise appears are high with one microphone tube (this one in particular) , so with 2 .........!
i had a bunch of 25 408A (JAN and WE) and i never found a quiet pair after many hours of tests...
So, i gave up !
i add that the doubled miller capacitance ( between 12 and 16 pF added to the capsule ) lowers the sensibility of the capsule and affects the signal noise ratio, thus the noise floor doesn't really comes down with paralleled tubes in a mic , quite the contrary ... !

However paralleled tubes are useful for Phono RIAA preamps ...

Dr Gris · Nov 12, 2014

melomane said:
I beleive the truth needs to be exposed to permits the real pionneer on this matter to be given the deserved credit.

Best regards, Flavio

I have the highest respect for Max and I truly wish I could afford a pair of his beautiful MK-U47, but I can't at the moment

This post seems to me that you Flavio want to tarnish Max's reputation. And why is that??
And now it's time for the truth to be exposed....
You are Yannick, also posting as micandmod, yankimusic and maybe more usernames...
Don't forget that when you post as "melomane" your name is Gino(as you've written before), not Flavio!

For those that don't know, micandmod(Yannick) & ioaudio(Max) aren't the best of friends.

To me, this is not ok!

Best regards
//Magnus (yes, that's my real name)

kcatthedog · Nov 12, 2014

Melomane,

To be frank, I found your whole post basically offensive, cus you presume a lot. I find Max to be an honest person and credible person and you much less so.

Next time you feel like posting something like this; do us all a favour and back away from the keyboard.

Pip · Nov 12, 2014

Gentleman! Does it really matter who invented what? The parallel tube idea is nobody's invention! But it is everybody's to use! This is only a partial representation of a lengthy discussion that is being used to effect some kind of social outcome.

This by no means will be the first time credit for an idea has been contested. Nor will it be the last. IOAudio has been a true contributor to this website for sometime and he has given to the community in a most generous way, also his metal work is art!

Saturn Sound has come underfire for there approach. Telefunken USA has come under fire for there's. So have others. In the end how does it sound and is it reliable. I would go on to say that sound is a subjective discussion at best and a science at worst. I have stated in my own posts that the 408a is a rather distortion ridden tube if used under the manufacturers recommended settings. I have built Max's mic and IMHO it sounds fine.

It has been put forward many times that maybe we should all start inventing new approaches to old problems instead of trying to recapture the artifacts of the past.

I own a lot of mics. They all sound different they are all unique. It has always made me laugh when people speak of the venerable U47 as "the mic Sinatra used" or "the mic the Beatles used"! People at the end of the day they were Frank Sinatra and John, Paul, George and Ringo, I'm gonna' go out on a limb here and say that there presence at the session had something to do with the outcome!!!

Live and let live!!! Don't be a hater!

granger.frederic · Nov 13, 2014

"IOAudio has been a true contributor to this website for sometime and he has given to the community in a most generous way, also his metal work is art!"

In fact , Ioaudio's intentions are, in fine , to sell his work on this site....(and he is entitled to...)

OneRoomStudio · Nov 13, 2014

We're dealing with the world of analog audio electronics here...practically no one has "invented" anything in the last 50 years.

Have people come up with new implementations of old ideas? Yes. Have there been advancements in lowering noise and/or improving the price/performance of old circuits? Yes. Have there been clever solutions to problems of discontinued parts? Yes.

Who cares about the rest?

I miss Oliver (as I'm sure many others here do) , but IO isn't doing him any disservice. The intention of this community has always been helping each other to create and build the best audio equipment possible. I believe that IO is upholding that perfectly. Is he making some money from his endeavor? Yes - but he should be. he should be able to benefit from the work he did in developing his circuit boards and kits. Saying otherwise is just a personal attack, and uncalled for.

ricardo · Nov 13, 2014

melomane said:
Saturn sound used both tubes the 407a and 408a, the 407a would have been labeled as UCC88 in the European tube code.

The 407a is 2x 20V/50mA version of the 2C51, what is in essence nothing else than a commercial grade ECC88 with a different footprint.

Is this the Saturn Sound replacement VF14m?

http://www.saturn-sound.com/products/replacement%20valve.htm

Marik · Nov 13, 2014

melomane said:
The 407a is 2x 20V/50mA version of the 2C51, what is in essence nothing else than a commercial grade ECC88 with a different footprint.

This is very strange. ECC88/6922/6DJ8 is a very special frame grid tube specifically developed for use in cascode circuits. It also has very specific--clean and analitical sound. While both 407 and ECC88 have similar mu (33-35), the transcoductance of the ECC88 is twice of 407, so the Rp is considerably different. It is enough to compare their graphs to see they are very different tubes.

Best, M

Moby · Nov 14, 2014

melomane said:
Hi Folks, I have been watching the whole polemic regarding the U47 dual 408a tube design The "Invention" of this particular configuration for the U47 clone from IOaudio & micandmod (or poctop).
after reading this article dated from february 2009 about a year before the MK47 came out , i can draw a conlusion pretty quick that this was not Ioaudio invention as he
claimed to be is. Oliver Archut was clearly stating that saturn sound was using this configuration way before the mentionned "Invention"about a year later down the road.
I beleive the truth needs to be exposed to permits the real pionneer on this matter to be given the deserved credit.

Just my 2 cents.

see here for more details....................................................

Reply #23 on: February 13, 2009, 09:22:31 am

http://repforums.prosoundweb.com/index.php/topic,28765.15.html

Or simply this ,

Hello guys,

Saturn sound used both tubes the 407a and 408a, the 407a would have been labeled as UCC88 in the European tube code.
The 407a is 2x 20V/50mA version of the 2C51, what is in essence nothing else than a commercial grade ECC88 with a different footprint.

Running both triode haves in parallel and the filament in series gives you a replacement tube for a VF14 that will work close to the specs of an VF14.
But of all the 407a tubes I found, none of them was mic grade material, even the so called 'super-tube' Western Electric ones did not meet the simple VF14 noise specs.

The 408a is na EF95 with 20V/50mA filament, so with a dropping resistor, a direct replacement could be archived.

But here again, not the WE/Northern Electric, nor the Ericson, that were supposed to be high grade tubes, are good enough to be used in a U47.

However, the 408a/VF95s specs are pretty close in impedance as well as technical data, the head room is about 5dB less.
The tube in the pic is not Ericson, WE or RCAs because it is missing the black nickel plates.

Putting a glass tube in an metal container might be marketing, but it is still a drop-in replacement.

If someone wants a U47, buy a Neumann U47 with a VF14. If you do not have the cash nor the cash to keep the great sounding museum piece running, get a new mic.

Best regards, Flavio

Are you serious? Invention? Paralel tubes are older than anyone here on the forum. What's a deal about it besides it has nontolerable input capacitance as the VF14 substitute?

ioaudio · Nov 14, 2014

Wonderful, all the haters united ;D

Capacitance of VF14 ~8 to 10pF http://www.radiomuseum.org/tubes/tube_vf14.html
Capacitance of 408a ~4pF (two in parallel = 8pF) http://www.mif.pg.gda.pl/homepages/frank/sheets/049/4/408A.pdf

Granger Frederic,

looking through my records i couldn't find your name so it seems you did not purchase any of of my kits.
If you did, you would know that the MK-U47 and MK47 are sounding great.

Thanks to those supporting me, you all made this possible!
Back to work now.

-Max

Moby · Nov 14, 2014

No hate, just a facts.
Vf14:
Grid to plate: 2.6pF
Grid to cathode: 6.7pF
Plate to cathode: 12.5pF
P.S. Did I told you that your U47 body looks great? If not, here I say

it looks wonderfull. Cheers

ioaudio · Nov 14, 2014

No you didn't tell me - thanks

Do you have any documents to substantiate your numbers?

Moby · Nov 14, 2014

Numbers I posted are measured values of the VF14 under U47 circuit. As we all know VF14 is low biased and uderheated heavilly in that circuit so the nubers are quite different from the pentode datasheet. Two 408's gives totally different measurings, but they work. Unfortunatelly I dont have those measurings with me, I gave up from that tube because I was not happy with the results. BTW, I don't think that VF14 tube is something special, especially for microphone designs but it works as it is under this circuit.
Again, no hard feelings, please. I dont have any problem with you, your work and your products, and I really dont want to start some harsh discussion. I just reacted because the word "invention". Just stay sharp and don't get me wrong if I react from time to time

cheers

granger.frederic · Nov 14, 2014

Dear Ioaudio,

no hate, but no need to buy your kit to mount two 408A in parallel in my U47, and to dislike that ...

i measured the capacitance added around 14pf even if the datasheets are giving a bit less

however, i thank you for your contribution in this forum

regards

ioaudio · Nov 15, 2014

Moby said:
As we all know VF14 is low biased and uderheated heavilly in that circuit so the nubers are quite different from the pentode datasheet.

Neither underheating nor biasing can have an effect on interelectrode capacitance.
Input Capacitance (Ce) is given for pentode and tetrode connections in the above datasheet.

I just tested the input capacitance of the 408a and vf14 on my bench to verify these numbers - 9pF for the VF14 and 8,5pF for two 408a's in parallel, just as the datasheet would imply.

Frederic, I don't know what happened in your experiment, but these are the numbers.

granger.frederic · Nov 15, 2014

if you just checked, it was surely a bad measure...
however this won't change my point of view

IOaudio Inventor of the parrallel 408a tube configuration in U47 Clone ?

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