Making My U47

Tab-Funkenwork has a schematic online for the U47 circuit using an EF14 instead of a VF14. Very useful you guys. Very.

Schematic Link

Skylar’s EQU47 mic bodies are almost (or already) in the mail! There’s been a lot of… complications… with the factory in China. As such, the mic bodies will arrive slightly less than perfect. The top portion of the head basket doesn’t have the correct “mesh biasing” which is a fancy way of saying the inner mesh isn’t rotated 45° to the outer meshes. It’s rotated 0°. There’s some debate as to whether this will have an effect. The way I see it, every active (read: electronic) part of this microphone won’t be a genuine original Neumann part from 1947, so it’ll be okay for the passive (read: mic body) parts to be negligibly different as well.

I’m sure it’s going to sound amazing regardless.

Admittedly, I’m a ponce. I don’t really know what I’m doing with this whole U47 business. I’m just a graphic/interaction designer with a silly dream: A dream to kick ass at building recording equipment. That being said, I’ve been boning up on my solder slinging by working on another project. 

Over the course of this summer, I’ve been working on the classic Royer microphone mod. For those unfamiliar: click here. Back in 2001, David Royer of Royer Microphones put together an article for Tape Op magazine (the only magazine I subscribe to). In it, he detailed how to turn really shitty chinese condenser mics like the MXL 2001—or my Apex430—into grade “A” pieces of tubular class. Once I discovered my Apex 430 had essentially the same body as the MXL 2001 I decided to go for it.

Normally I’m a New Yorker, but I’ve spent the last 3 months in San Francisco interning for a popular computer company. As soon as my plane hit the tarmac I was on Mouser.com ordering parts off the BOM (Bill Of Materials).

This weekend I finished, just shy of 3 months later. Most of that time was spent waiting for parts. The US post office lost one of my original orders from Mouser, so I spent the better part of a month waiting for it to get unlost, only to finally give up and re-order everything. Once I got the initial boards populated and most of the power station completed, I ordered a microphone output transformer from Sowter (the 4935f for those interested). It was a smart choice in retrospect, but I had to wait a month for them to hand-wind and ship it to me from Ipswitch England. It’s a special thing.

I nearly electrocuted myself a dozen times in a single day when trying to debug the power supply, but when all was said and done the microphone sounds fantastic, and burn marks will heal. I learned a ton.

I set it up alongside my Soundelux U195 and I have to admit… it sounds better. It’s less hyped in the highs and more transparent, and I haven’t even replaced the capsule yet! I’ll be putting in a Peluso capsule in the near future and may add a polarity switch for the extra zing.

Oh, the thrill of victory.

… and man is it gorgeous. I’ve already pre-ordered mine! You should do the same.

- David Pogue on the iPad.

The concept of “consuming” vs. “creating” and a device built for one rather than both was particularly interesting. How can begin to disperse the needs of “creating”? How can we free creation from the tyrannical cyclops known as the computer?

The Telefunken VF14 Tube used in the original U 47s has become incredibly scarce. To purchase a NOS (New Old Stock - a 70 year old tube kept in a deep freeze) VF14 can cost between $1500-$2000… if you’re lucky, and that price is only going to go up as the years march on.

So, you’re faced with some options in building your “new” “U 47” microphone. You can plop down $2000 and get your true-to-life original VF14, or you can find a suitable substitute like the EF14, UF14, or… dare I say it… even the EF86.

The VF14 was made by Telefunken in the era of the tube based AC/DC radio receiver. Sadly Georg Neumann chose this tube for his fated microphone just as that market was beginning to dry up. Telefunken shortly thereafter chose to discontinue the production of the tube due to cost issues. Since the VF14 wasn’t made for use in microphones, it wasn’t quite suited for the spec, so a high percentage of the tubes were ill-matched for use in the U 47. Those suited for use in microphones were marked with an “M.” So if you’re buying a VF14, look for the VF14M.

Disclaimer: If you’re restoring a true U 47, get a VF14. Just do it. The amount of value your mic will lose with another tube + the alternate wiring you’ll need to compensate will equal far more than just plopping down the $2000. It’s egregious, but what can you do?

Now, you must understand that ANYthing other than an original VF14 will make your U 47 a bastard child in the eyes of the purists. And absolutely… it will not be a “true” U 47. So, purists… read no further! Turn back now! Abandon all hope, ye with sticks up your butt!

I’m not restoring a true U47. I’m building a mic from scratch. I have no inherent value to lose. So I’m going to use a different tube, and—if you’re building your mic from scratch as well—I think you should join me. My top choice is an EF14, which is identical to the VF14 in every regard, except for two. Number one: it requires 6V instead of 60V for the heater. Number two: it costs about $1800 less than a VF14. Why am I sure that the sun will still rise tomorrow if I use an EF14 and not a VF14? Well, Wunder Microphones, which makes fantastic U 47 replicas, specifically states that they use EF14s in their remakes and that the use of a VF14 isn’t worth the increase in cost. I’m sold. How about you?

Now, if you’ve been studying up like I have, your next question will be: “Russ, the original VF14 heater was notably underpowered for its application in the microphone. If the heater voltage is different in the EF14, do we still have to underpower it?” The answer is yes! power the heater of your EF14 with only 4.95V instead of the 6V indicated in the spec sheet. All else should take care of itself.

The other benefit of the EF14 is that it is shaped exactly like a VF14. In fact, if it weren’t for the “EF 14” marked on the top, you couldn’t tell the difference. This means, that if at some point down the road you go all Daddy Warbucks and purchase a VF14, you can slide it right into the EF14s place, make a couple mods in your circuit, and you’re good to go.

Bueno.

From Skylar:

I’ve just started production, so the pre-ordering will begin late January at the earliest or February.

Stay tuned.

Did I mention I was excited? I am.

In light of this, I think I can effectively cross the body off of my list of things to make. Rad. After thinking about it, I think I’ll be attempting to put together the power station unit and see if I can get that all together. Now, to source some PSU plans!

Skylar Gray’s early Solidworks mock-up of the u 47 body. Nice.

In doing my research on the body of the U 47 microphone I stumbled upon something amazing. I was looking for rough information the bodies dimensions, the mesh, any insights into how one might construct one from scratch, as well as if anyone was currently making a hollow shell resembling a U 47, etc. etc. Anywho… I stumbled upon this tome of a forum thread:

http://www.prodigy-pro.com/diy/index.php?topic=30742.0

HOLY CRAP! It took me two days off and on to read through the whole thing. If you’re interested, it reads a bit like a novel, the conclusion of course being that this group of people (with the help of a brilliant designer named Skylar Gray out of Oklahoma—image at left) seems to have pooled their resources to create a near perfect replica of U 47 body, down to the wire mesh, the metals used, and the screws used to hold it together.

The post was created almost a year ago, so as soon as they started talking about making their own body I thought, “this can end one of two ways. Either this project isn’t possible and fizzles out or they’ve somehow made this already and my opportunity to get one has come and gone.”

Lo and behold! I get to the end of the post (which has been exactly one year in the making!) and find that the project is still ongoing and that I may have a slight chance of getting one of these short run mic bodies! Needless to say this would be an amazing step forward. The grill / headbasket is one of the 4 most important pieces in the sound of the u 47.

I’ve contacted Skylar and asked if there are any spare bodies left unspoken for. Cross your fingers!