EF12K conversion for U47-style mike. 408a any experience?

[ln76d]

I'm starting to think about a new project to do
For now, I'm at the stage of gathering information. For any information or help i'll be appreciated. In particular, I have a request to Stewart Tavener, who made his STU47.
Is there any complete schematic with conversion U47 from VF14 to EF12?
Does anybody have a schematic of Siemens/Klangfilm U47?
I've read that this u47 incarnation had a EF12 originally.
I want to use Chinese microphone as a donor of housing.
Flea or AMI housings are great, but not for my pocket.
What clone of BV8 do you recommend? Does anyone have experience with advanced audio microphones BV8? It is quite cheap Does anyone know where in Europe I can buy a good equivalent of BV8?
I would like to use the Thiersch M7 capsule, in fact it will be probably cheapest option, since i live in europe
How best to get started in the power supply issue? I've read quite a long thread on the forum about U47 and EF12, but i didn't get any good point to start from it
I can order any power transformer, so I do not need to drop voltage by an additional resistors. If someone has idea for simplest as is possible PSU and want to share it, i'll be thankfull.

 

[zebra50]

Hi!

My mike wasn't a conversion from the U47, more of a mic inspired by it. The schematic is here...

http://www.xaudia.com/omnip/Mics/STU47/STU47schemo.png

I used one of Max's (IOaudio) transformers. I've also had a good result with a Cinemag BV8 type.

However, the main problem I had with this was finding a quiet EF12, that would stay quiet. It took a few tubes and I'm still not entirely happy with the noise level on this one.

Anyway, good luck, and let us know how it goes.

Stewart

 

[ln76d]

Thank you Stewart for quick reply and schematic. For now i'm searching some information 
I found ioaudio sales topic and send pm for bv0.8 price.
I didn't realize that ioa is from Austria, so it will be good option.
It's a really a lot of things to search. Now i'm reading 408a tube info on K.H. forum, it starts very interesting Maybe this will be better way than EF12?
Prabably completing parts takes me a lot of time but i'll try to put some infos in time.

Cheers

 

[zebra50]

No problem - take your time in the planning stage and the build will go a lot better.

I have a stash of 408A tubes so drop me a line if you need one or two. They have a 20V heater so you can wire them in a similar  way to the VF4.

 

[micaddict]

However, the main problem I had with this was finding a quiet EF12, that would stay quiet.

You may wanna try these:
http://www.beesneezmicrophones.com.au/store/index.php?_a=viewProd&productId=55

It's in the BeesNeez Arabella, too.

 

[ln76d]

No problem - take your time in the planning stage and the build will go a lot better.

I have a stash of 408A tubes so drop me a line if you need one or two. They have a 20V heater so you can wire them in a similar  way to the VF4.

Thank you Stewart!
I think to try JAN 6028, maybe it will be a little bit better?!?!
In two issues I'm more inclined to use a 408a/6028. Easy to adapt to the circuit, and this is probably the "magic" tube VF14K from Tele-US and also possibly Saturn Sound RV14.
I want to wait for ioaudio housing pricing. For now i didn't get answer on a price of bv08. Maybe Stewart you know, what's the price of this tranny?
Equinox produce very nice housings and price is not so high, but with shipment, tax and duty this price rise up too much.
What's will be better? Use a carbon resistors or metal film?
Are there any good low noise carbon resistors which are worth to use in mike?
I know only that many people likes allen bradley non inductive carbons, but i've read many bad opinions on them too.
I don't want make a new topic, so i ask here Could you Stewart tell me, that the three layer enameled wire will be good to rewound Reslo rb tranny?

 

[ln76d]

However, the main problem I had with this was finding a quiet EF12, that would stay quiet.

You may wanna try these:
http://www.beesneezmicrophones.com.au/store/index.php?_a=viewProd&productId=55

It's in the BeesNeez Arabella, too.

Little bit pricey, i see those tubes sometimes for very cheap, if someone needs this tube i can look for it.

 

[ln76d]

Do someone has experience with 408a/6028 tube in his clone/style or genuine U47?
Is there any checked mod with makes improvement or only this one grid resistor to add? ???

 

[micaddict]

Little bit pricey, i see those tubes sometimes for very cheap, if someone needs this tube i can look for it.

Last year, a guy in my country offered hundreds of those. So, apparently those are not rare (yet) which keeps the price down.
This does not mean they can't be great sounding tubes.
Also, the ones that Ben offers might be selected for low noise and microphonics.
And Telefunkens (those that are left), despite the high price, can have their problems.

 

[micaddict]

In addition to my last reply, I'll post a quote by Ben, from the Gearslutz forum (December 2011):

"The 6X8 or 5693 or 6SJ7 tube that we use in the Arabella is an amazing tube, the tube is so exceptionally quiet and sounds as you are all aware; amazing. In the very beginning with the Arabella Studio Series mics, we were using Telefunken EF12 tubes as we had a nice supply of them on hand, this stopped when we transitioned to the Producer series due to noise and supply issues. The EF12 tube and the 5693 are an equivalent tube to one another but the 5693/6X8 tube that we are using has a lower self noise and the frequency response is unaltered from the EF12 so we decided that this was the way to go with the Arabella.

We have now over 2000 Arabella's in the market in daily use and we ship perhaps 3 - 4 tubes per year to our customers due to noisy or non working tubes, this is outstanding quality and unmatched by any other tube that we currently use."

 

[ln76d]

Little bit pricey, i see those tubes sometimes for very cheap, if someone needs this tube i can look for it.

Last year, a guy in my country offered hundreds of those. So, apparently those are not rare (yet) which keeps the price down.
This does not mean they can't be great sounding tubes.
Also, the ones that Ben offers might be selected for low noise and microphonics.
And Telefunkens (those that are left), despite the high price, can have their problems.

You did overinterpretation of my post
I don't doubt, that thes tubes sounds good. I do not condemn beesneez for sale in this or that price. If these tubes would be unique, probably they would be in several times more expensive price I just write the fact that I sometimes see them quite cheaply. Beesneez have a little further than I to  Russia, so it also may explain the price. In my country, most of russian Tubes (which most of them are really good) are cheap, is because it's lot of them. I do not condemn other retailers tubes that are not worth the money but with reason or another are sold expensively. If there is a customer who wants to buy, it is of course only a matter of the seller and customer. This is not my issue at all
Some sellers/manufacturers must sell even cheap parts in higher prices, because if they want to be in a higher level on the market, cheap means for they brand a suicide.
Glory for the fact that there are companies such as beesneez or (often attacked) TFK-usa and many others!

 

[micaddict]

You did overinterpretation of my post

Could be the other way around, too. 

If these tubes would be unique, probably they would be in several times more expensive price

Hard to be unique maybe, with so many around.

I just write the fact that I sometimes see them quite cheaply.

Agreed (again).

In my country, most of russian Tubes (which most of them are really good) are cheap, is because it's lot of them.

Exactly. But they might still be very good.




Anyway, question is, have you tried them?

 

[benqbasic]

Hi.

I'm quite interested in this topic of EF12k, 408a and 5693 tubes.
I made a ef800 U47 type mic last year but I'm planning to build another U47 type mic this year.

I was planning to use a EF12k. But i keep seeing this 408a tube turn up in thread but haven't found anyone who has build a mic with it.

Does anyone know about using these tubes in this circuit and how they compare?
I'd also be interested if anyone knows how the heater and bias circuits are set up in the wunder U47's (or the like) that use the EF12k.

Sorry to hijack the thread.

 

[ln76d]

I was planning to use a EF12k. But i keep seeing this 408a tube turn up in thread but haven't found anyone who has build a mic with it.

Does anyone know about using these tubes in this circuit and how they compare?
I'd also be interested if anyone knows how the heater and bias circuits are set up in the wunder U47's (or the like) that use the EF12k.

Sorry to hijack the thread.

Your not hijack the thread - more people, more info, more fun
Threads like this dying very quickly, so i'm happily that you wrote
What i now, that is the 408a you can use direct in original circuit only with adding one grid resistor.
As i mentioned in this topic, this is (probably) VF14K from Telefunken US.
Many info about this tube are on the Klaus Hayne forum.
What body and transformer did you use before?

 

[benqbasic]

Your not hijack the thread - more people, more info, more fun
Threads like this dying very quickly, so i'm happily that you wrote
What i now, that is the 408a you can use direct in original circuit only with adding one grid resistor.
As i mentioned in this topic, this is (probably) VF14K from Telefunken US.
Many info about this tube are on the Klaus Hayne forum.
What body and transformer did you use before?

Thanks,
I used a Aurycle A5500 kit but only used the body and psu (which I rebuild the heater circuit.)
The transformer was from advanced audio (aamicrophones.com). They are the same as the smaller peluso bv8p. PIO caps and carbon comp resistors, etc.
The circuit was the Oliver Archut alternative tube schematic.

I was reading the 408a has less bass. Which seems to be in keeping with the new telefunken u47 clones.
There is some info and tests done on this tube on the other forum topic,29577.15.html.

Im also wondering what difference running two in parallel does eg ioaudios mk47.

Cheers,

Ben