Circuit comparison MK47vs AMI alternate U47

[gary o]

Just incase anyone interested I built a mic a couple years back, circuit was as maxes MK47 ie 2 X 6028 tubes philips in this case I didnt use a PCB board I did point to point not even a tag board, power supply was max desighn too 105V & max OP transformer, I used a equinox body and the most important part the capsule its a Violet design Vin 67 its was about £500 on sale a few years back it was in a lollypop head, its meant to sound like a U67 mic, I dont have a real U67 to say that it does or not but the capsule when used on Violets own flat solid state mic body is said to sound like a U67 its got good reviews..... so basically its a quality capsule but its not gonna sound like a U47 for sure.

Yesterday I soldered together Olivers alternate U47 circuit I used a (well 3)  Mullard EF80  I swapped out the MK47 electronics even left the same OP cap a russian paper in oil 1uf, I modified the power supply added extra PSU for the filiment 5.05VDC.

before changing circuits I recorded vocally a verse of a song with MK47 & then same verse with the AMI I tried the 3 Ef80s I had

Result well to my humble ears if im honest I couldnt hear a difference, if there is difference its so small that I could sing a different take to make sound different, I kinda expected this result as I believe thru many experiments like this that the capsule is way by far & I mean miles the most important component of a mic, I know transformer is fairly big part & head basket next op capcitor.... after both these circuits were based on and designed to sound like & behave like U47 circuits so both guys did good job i guess.... I like the sound of my Vin 67 in either circuit I prefer it to my real U87ai tho I would love to get a real K47 K49 M7

( by the way I have ordered a real U87 transformer to add to a vintageU 87 circuit I already build & I will add my 87capsule in its head basket so I can AB U87ai Vs vintage style U87)......coming soon.....

 

[ln76d]

It's not clear to me do the Vin67 emulates K67 capsule or sound of K67 in U67 circuit.
Is it more flat or the highs are boosted? In both ways i believe it's brighter than M7 and there's no peak in high-mid.
Different response of the capsule can mask some details in preamps differences.
If someday you would like to sell lollipop head enclosure in reasonable price i might be interested, definitely not now - i'm broke right now

 

[gary o]

Will try to clarify the Violet design Vin67 lollipop head is designed to sound like a complete U67 microphone (not a k67 capsule) that is providing the mic electronics have a flat sound, no de emphasis....... to me its sounds nice in all mic circuits I have made other than if circuit had de emphasis.

Point Im making is the electronic circuit of mics compared to the capsule makes a waaaaay smaller difference than the capsule.. for instance I have another nice capsule from Tim cambel I have tried both capsules in lots of mic circuits & the Vin67 always wins for me everytime its shines thru the circuit

 

[ln76d]

I agree of course with you and i'm a huge fan of Mr Zarins capsules and circuits btw
Biggest difference you will get with transducer if we agree that the preamp isn't "broken".
With tube circuits i think you could hear more differnces when you will try some capsules with bump in upper midrange - M7/K47.
If you will have the opportunity, try even chinese K47, it has higher bump than original capsule.
Other thing is, how the both circuits sounds comparing to the real U47
Btw. there's a thread of my (future) build based on u47/48 circuit.
Idea is to make cheap good mike, not a "clone" of u47.
I have enough different parts which laying around, so why not
Right now it is little bit mixed thing - it use single 6028 with seperate heaters.
Since yesterday,  when i realized how stupid i am, it use similar arragement of cathode - like in Oliver circuit.
Other thing is that  it will be three polar pattern mike.
If you will have any ideas for that circuit - you are welcome 

 

[Banzai]

Link?

Thanks!

Btw. there's a thread of my (future) build based on u47/48 circuit.

 

[ln76d]

Link is not worth anything i abandoned that project because typical u47/48 circuit can't use 408a/6028 (after tests) - i don't know how tele us (if this true) can use single 408a for their 47.
I changed the circuit for something much more suitable for this tube and full optimized - microphone is really great, so if you are interested to use this tube - try it! Worth.

http://groupdiy.com/index.php?topic=62423.0

BTW.  please remember about psu photos and rest of info

 

[Pip]

Link is not worth anything i abandoned that project because typical u47/48 circuit can't use 408a/6028 (after tests) - i don't know how tele us (if this true) can use single 408a for their 47.
I changed the circuit for something much more suitable for this tube and full optimized - microphone is really great, so if you are interested to use this tube - try it! Worth.

http://groupdiy.com/index.php?topic=62423.0

BTW.  please remember about psu photos and rest of info

They don't! They do use the 407a! It may not have the characteristics of a VF14 but then again nothing really does. The bottom line is if you parallel the plates and series the filaments it gets close enough for government work or IMO to dupe the mic buying public. The meat of any mic for my money is the Capsule and the transformer. The impedance converter (tube) can be substituted with good if not better results.

Lets be real for a moment about the VF14 no matter how good a U47 sounds with an M designation VF14. The VF14 was chosen not for its of the assembly line ready characteristics but for its at the time mass production and that it worked well in a single voltage supply schematic. They went through hundreds to find the hand full of VF14's that made it to the M class. At one point in time almost every radio receiver in Germany used two of them. That meant tons could be tested. It is also a fairly microphonic tube thus the damping ring was employed. It is in this DIYers view a ship that has sailed and ain't coming back.

 

[ln76d]

Link is not worth anything i abandoned that project because typical u47/48 circuit can't use 408a/6028 (after tests) - i don't know how tele us (if this true) can use single 408a for their 47.
I changed the circuit for something much more suitable for this tube and full optimized - microphone is really great, so if you are interested to use this tube - try it! Worth.

http://groupdiy.com/index.php?topic=62423.0

BTW.  please remember about psu photos and rest of info

They don't! They do use the 407a! It may not have the characteristics of a VF14 but then again nothing really does. The bottom line is if you parallel the plates and series the filaments it gets close enough for government work or IMO to dupe the mic buying public. The meat of any mic for my money is the Capsule and the transformer. The impedance converter (tube) can be substituted with good if not better results.

Lets be real for a moment about the VF14 no matter how good a U47 sounds with an M designation VF14. The VF14 was chosen not for its of the assembly line ready characteristics but for its at the time mass production and that it worked well in a single voltage supply schematic. They went through hundreds to find the hand full of VF14's that made it to the M class. At one point in time almost every radio receiver in Germany used two of them. That meant tons could be tested. It is also a fairly microphonic tube thus the damping ring was employed. It is in this DIYers view a ship that has sailed and ain't coming back.

Again (i think) - show me the proof for 407a.
In my opinion and what i know (all my links gone with a hard drive) they use single pentode not a double triode.
It's not about any magic of VF14 or any other bulshit - only basic specs (impedance for example) which don't fit the circuit without changing resistors values, transformer ratio and other conditions.
Despite all the fake u47 and which tube telefunken use - single 408a isn't proper for 7:1 ratio transformer due to higher impedance and even two tubes in parallel.
Impedance converter matters as hell - need to be properly tuned to work well or any other equivalent tube  need to fit with similar specs or circuit condition need to be changed.
Someone other said here that most important is headbasket in U47, you are sayng about capsule and transformer.
Both opinions are not worth anything for me  - to be honest.
Everything matters.
Try two-three different arrangements of the tube input/capsule output - you will get different sensitivity - different sounding microphone. Different type of biasing, cathode capacitor or without and much much more.
For transformer - due to fashion (easy to change, especially for people which build microphones or kits like a monkey with a blocks) there's a hype for transformer sound. Make A/B with let say BV08 and any other good transformer (doesn't mean expensive) which have same ratio and similar frequency response  - you want a bet that you don't hear the difference??
Different thing are transformers with drop in frequency or saturating easily.
My two cents.

 

[Pip]

I think we agree, it does not work. I don't think that either the 407a or 408a really replace a VF14M in a U47 but the only point I am making is that that hasn't stopped these manufacturers from using them or from people using them in U47 copies/wannabies (I hate the term clone). And as I said before I think that some of these companies IMO are duping the mic buying public.

I myself have built many copies from alternate schematics put forward by other people, most significantly Oliver Archut of Tab-Funkenwerk and Max Kircher of IOaudio. Oliver touted the EF80 and EF800 both cousins to the VF/EF14 as very suitable replacements for VF14. I have had both good and bad results. Some of them have been great tools for recording and others are sitting on shelves.

There are over the course of the U47 life span at least three major variants on circuit and body that I am aware of not to mention the evolution of components both electronic and aesthetic. Read Allen Sides comments on the headbasket plating variant. He claims it makes a massive sonic difference.  And you have read the Moxtone contribution.

The only point I  was trying to make is that of course it is a holistic approach but that the maths don't always trump the sonics.

From the Telefunken US website:

After considerable research, TELEFUNKEN Elektroakustik located a glass tube, of obscure origin, originally manufactured for use in transoceanic telephone transmission. This tube captures all of the “ magic", "vibe" and "mojo" of the original tube. This is not a Nuvistor tube, nor an EF86, both of which have been previously used as substitutes for original VF14's. By carefully modifying by hand the actual physical shape of the tube, it is able to be placed inside an enclosure with identical pin orientation as an original VF14. The resulting sonic characteristics are extremely close to the original VF14, with nearly identical gain and distortion measurements.

Count the pins that are visible I think that there are 9 but it might be 7 it does look like a single plate as well so you might be right. But it is hard to tell.

 

[micaddict]

IIRW according to Max, an original U47 PSU (without alterations) will work on the MK47.

Any comments?

 

[ln76d]

And?

 

[ln76d]

Some of them have been great tools for recording and others are sitting on shelves.

Probably few changes in circuity and they will work good

There are over the course of the U47 life span at least three major variants on circuit and body that I am aware of not to mention the evolution of components both electronic and aesthetic. Read Allen Sides comments on the headbasket plating variant. He claims it makes a massive sonic difference.  And you have read the Moxtone contribution.

I didn't say it have no impact - i said that all have the impact
It's much more related to all these kit-ers - which believes that if someone call anything  U47 - they will get U47...
This is sad.

The only point I  was trying to make is that of course it is a holistic approach but that the maths don't always trump the sonics.

It's not about the math either - but if something doesn't fit specs - it's not equivalent, if something doesn't sound right - it's not equivalent. It's like you will use tractor wheels in the porsche.

From the Telefunken US website:

After considerable research, TELEFUNKEN Elektroakustik located a glass tube, of obscure origin, originally manufactured for use in transoceanic telephone transmission. This tube captures all of the “ magic", "vibe" and "mojo" of the original tube. This is not a Nuvistor tube, nor an EF86, both of which have been previously used as substitutes for original VF14's. By carefully modifying by hand the actual physical shape of the tube, it is able to be placed inside an enclosure with identical pin orientation as an original VF14. The resulting sonic characteristics are extremely close to the original VF14, with nearly identical gain and distortion measurements.

Count the pins that are visible I think that there are 9 but it might be 7 it does look like a single plate as well so you might be right. But it is hard to tell.

Previously they make statement that this is full metal body tube made by them...
They had to change that statement when fraud was discovered
I love the words  “ magic", "vibe" and "mojo" - this what people buying, not the microphone but exactly “ magic", "vibe" and "mojo".
With an emphasis on "magic" - real hocus pocus,
People will believe anything, even the greatest nonsense.


" By carefully modifying by hand the actual physical shape of the tube " - my translator translate this as:
We had to cut off pins and the tip of the cheap tube to fit it to our cheap fake housing to sell you it as something valuable and rare.

"The resulting sonic characteristics are extremely close to the original VF14, with nearly identical gain and distortion measurements." - this part i commented before.

407a have thicker bulb than 408a so the fake VF14 looks much more like 408a.
Compare also shape of the top and base of these tubes.
http://www.radiomuseum.org/images/tubephoto_klein/407a.jpg
http://www.radiomuseum.org/images/tubephoto_klein/408apix.jpg

407a in parallel is the 20V same as 408a.
Lets look for current.
408a - 50mA
407a - 100mA
With additional 160ohm resistor inside fake housing:
408a - around 18V heaters
407a - around 10V heaters
10V would be too risky for commercial purpose for little glass tube and the heat would be insane - with the real VF14 heat is high as hell so imagine drop to 10V.
So if the 407a - they will need to use it in series - then 40V and 50mA - so what for additional 160ohm resistor?
Without it - heaters around 33V and with  - around 31V.
Deosn't make sense.

 

[granger.frederic]

TFK  vf14k is a 408a with a dropping heather resistor
works quite fine but ....

i'm not a big fan till the beginning even if Max's work is very respectable, there are some issues...
i debated about it in many posts for a  long time , attracting the attention of various interested membrers ,if you know what i mean...  :

i'm a bit lazy to write again the explanations thus they do the job for me ,

look and read carefully : http://phaedrus-audio.com/VF14M_story.htm

even if they'are in the business , everything makes sense to me

regards
Fred

 

[Pip]

I am working with the Phaedrus product right now. I am waiting to discuss what the results are until I am done. I have a good feeling about this though. It is built quite nicely.

 

[JessJackson]

I have a u87ai here and I swapped the tiny 1uf elect for a nos tantalum drop, massive difference. elec is main reason u87ai sounds harsh and spitty.

 

[micaddict]

I have a u87ai here and I swapped the tiny 1uf elect for a nos tantalum drop, massive difference. elec is main reason u87ai sounds harsh and spitty.

Interesting.

 

[ln76d]

I have a u87ai here and I swapped the tiny 1uf elect for a nos tantalum drop, massive difference. elec is main reason u87ai sounds harsh and spitty.

Same way i changed girlfriend - massive difference, previously was harsh and spitty.
Anyway how this is related to the topic here?

 

[Pip]

I have a u87ai here and I swapped the tiny 1uf elect for a nos tantalum drop, massive difference. elec is main reason u87ai sounds harsh and spitty.

Same way i changed girlfriend - massive difference, previously was harsh and spitty.
Anyway how this is related to the topic here?

Ouch!

There are those that would say that tantalum makes the mic sound "tubby" as in fat around the middle. For everything you give you get if you know what I mean.

I an attempt to go back on topic.

The MK47 is layout and circuit wise very different then the AMI(Archut) variations and IOaudios MK-U47 much more in line with AMI variants as both try to be very close to a U47. MK47 all PCB layout others PTP. Read the threads. Most significantly the MK47 uses a transformer that is not a multi-bobbin design like the Bv8. Also remote relay for pattern. 

 

[JessJackson]

I have a u87ai here and I swapped the tiny 1uf elect for a nos tantalum drop, massive difference. elec is main reason u87ai sounds harsh and spitty.

Same way i changed girlfriend - massive difference, previously was harsh and spitty.
Anyway how this is related to the topic here?

Related like you and your girlfriend