Roman you're such a legend with your posts for the EU groupdiy'ers. all that import stuff really makes things so hard to build.I am really happy to help!
For everyone: There's another Euro supplier of rare audio parts, which does international shipping. Expensive, but they have things that are hard to get anywhere else. As I came across this site too late, I had bought my Haufe there (currently out of stock and quite pricey)
Online-Shop for daka-ware knobs, trafos, shielding sheets, inductors, frontpanels, iec-jacks and more
And if you guys are done fiddling around with colourful electronic ants and lemon drops and want a traditional version of a U47 that really looks, feels and sounds like one, simply drop 6 grand (instead of 25-30k on the market) and buy Andreas Grosser's masterpiece (don't get mislead by the partly disturbing picture selection, it's high-end, faithful to the original all the way)
Hello, I've been researching the great task of building a U47 clone. First off, I am no greenhorn when it comes to building DIY projects. I have many under my belt I am however, new to the mic DIY side of things. I've seen kits on numerous websites that go from 799 on up. I've seen BOMs, capsules, mic bodies, PCBs, etc etc on different websites. Many are from 10+ years ago to more current Mic & Mod type deals. Needless to say its all very confusing. I'm convinced that I personally would like to just gather all the parts myself and just build. I wish there was just a current PDF of what exactly is needed and where to source. I just seen what you have posted and would be very interested in going this route. Any help, guidance, BOMs, Websites, contacts, etc would be greatly appreciated. As a side note, I am not an electronics engineer just a guy that loves to solder and use what I put together in my project studio.
I had issues with hum in my M49b. I had the PSU circuit board grounded by the 0V connection by the transformer at one of the PCB standoffs' chassis hole. If I moved the ground near the choke the hum would increase. I thought the case was too crowded (Hammond enclosure) so I rebuilt it in a larger case from dandeurloo. Same issue.
I turned out to be a ground loop because I grounded the PCB from the transformer side of the PCB to roughly centre of the chassis. I moved it to the mic cable connection to the PCB and grounded it on the 7 pin XLR mounting screw and the hum was gone.
Grounding is hard to describe so I made a rough sketch. I made a forum member mad once for suggesting a ground lift as shown in Neumann schematics; so to be clear:
1) the power supply chassis is always bonded to earth ground via ground connection at IEC outlet
2) the mic body is always bonded to the power supply chassis via mic cable shield (and sometimes extra "screen" conductor bonded to shield)
3) the Neumann grounding scheme (see U67/NU67 schematic) has 0V, screen/shield and mic body all bonded inside the mic
4) the U67/NU67 has a switch on the screen (pin 3) which is probably preferred over switching 0V
5) I put the switch on the 0V because the shield will always be bonded to the power supply chassis via XLR housing and I omitted the screen (pin 3 in U67 schematic) on my M49 to add relay control over omni only mode
Best resistors for U47 are both 100M . 60M resistor was used with 0.5uF coupling capacitor in U47. This 60M-0.5uF version was built for radio broadcasts , it has less low end than 100M-1uF version. Sometimes, 60M-0.5uF version even better: for vocal or other instruments ( natural low cut). Grid resistor ( as a part of the highpass filter of the first order) and coupling capacitor (as part of a second-order highpass filter) affect on cutting of low frequencies. But, already a grid leak resistor 100 M you have 3 Hz filter cutoff. It is sufficient to apply the microphone in a studio.1G - too high value(!!!!) for most of old tubes. It is believed that higher grid resistor value may increase low end. But in reality, you will not hear marked increase low end in comparison with 100M. Even smallest fluctuations temperature or humidity will cause fluctuations of 1G resistors value, - it is not good. Of course, you can use laquer for avoiding of humidity influence. But that, huge grid resistor may also affect on stability of work of the tube. Use normal value- 100M, believe me. I tried 220M grid resistor with a few types of old German steell tubes (including VF14M), for example, and I did not hear any pleasant improvement in sound.
There were no big differences between historical BV08 transformers concerning its parameters , inductance, impedance etc. So, there was no other reason for decreasing of coupling cap from 1uF to 0.5uF,- only to reduce low end, which was undesirable for usage of U47 in radio broadcasts. With simple program- simulator you can find that with 1uF you will get ~30Hz resonance . When you use grid resistor 100M ( first-order high pass filter), frequency response is linear with 1uF cap. If you reduce grid resistor value to 60M, than with 1uF cap you will find decrease of useful low frequencies from 100 Hz, already. it is not good. That's why, if you use 60M you should also decrease coupling cap value to 0.5 uF. 0.5uF cap produces resonance~40Hz. Linearity with 60M-0.5uF will be recovered.
So, with 100M-1uF and 60M-0.5uF you will have linear freq. response, but in first case you will have low end a bit deeper in very low frequencies.
I'm a little late, but it took me a while to gather everything. Looks like you got some other good responses in the mean time.
I spent a good year+ researching my build and changing my mind on stuff repeatedly as I became more informed. There's a TON of ways to go about this. Nothing's right or wrong, so long as it works in the end. I'll start with some options for the build, and then some general "good to knows" that I picked up as I went along... also, yes, my build is now finished (and working well!). Shame on me for not updating this thread.
Vintagemicrophonepcbkit.com is probably the best u47 source to start with. Dan offers PCB kits, a Mouser bill of materials, and a number of specialized parts... including the highly accurate reproduction u47 body I used for my build.
Be careful not to just copy and paste Dan’s bill of materials. Of course, you’ll have to swap out-of stock-parts, but more importantly it’s good to really understand what parts you’re buying and why. Otherwise, you’ll buy everything twice (don’t ask me how I know).
D-47 - This is a PCB kit for a 6028/408A based u47 along with a classic style 105vdc PSU. Even if you don't use the mic PCB, this kit is worth it's price just for the PSU PCB.
D-EF47 - Similar style of kit to the one above, but based on an EF800 tube. This power supply works differently than the classic style: it sends two different voltages to the tube instead of just one. This is to accommodate the 5v heater in the EF800 (vs 35v for a VF14).
Dan's u47 Mic Body Kit - I'd suggest emailing Dan before placing an order on this page. He'll let you know what the wait time is going to be. It took a couple months for mine to be ready. Totally worth it. Cost was somewhere around $900 when I purchased, so this is if you want to go high end.
AMI Body Kits - I have no experience with these, but they seem legit.
Beesneez body kits - These things are built like a damn tank. Quality control kinda sucks in my limited experience though. Ended up sending mine back and choosing a different route. It was pandemic times and I suspect Beesneez was struggling to keep the business working, so I'll refrain from judgement.
Studio 939 MK47 Body - This body was already mentioned in a previous comment, but I’ll include it here as well. Too cheap for my taste, but if budget is your priority, this will do the trick.
Dan's D7 Microphone Capsule - This is the capsule I'd buy if I was starting again.
Beesneez K47 - This is the capsule I used. No complains about it, but I wasn't as aware of other options at the time.
BV8R is the one I chose. They'll all do the job. Make sure to factor in the physical dimensions of these and plan how you’re going to mount them.
AMI BV8R - Enhanced response, 4 screw mount holes.
AMI BV8Classic - Original response, 2 screw mount holes.
CM-2461NiCo - Enhanced response, no screw mount holes.
You can't really find an original VF14 tube. In fact, it's pretty hard to find any similar variant (EF14, UF14, etc) that isn't microphonic or noisy. The most common solutions to this problem are to utilize twin 6028/408As or an EF800. These of course require some slight modifications to the microphone circuit. The other option - and the one I chose - is the Phaedrus Audio VF14M. It's a solid state design, but it retains the tone and footprint of an original VF14 with no changes required to the microphone itself.
In summary, you're options are:
- Twin 6028/408A
- VF14 (lol, good luck)
Analog Vibes PSU Chassis - This one's better and is pre-drilled for Dan's PCBs.
Collective Cases PSU - I used this one.
Teflon insulated silver plated wire - This is the wire I used inside my microphone. It’s about as high quality of hookup wire as you can get. End stripping is a bit of a pain with teflon. A thermal wire stripper helps a lot. The wire is also available by the foot at TubeDepot in 20 gauge and 18 gauge.
Gotham Cable GAC-7 Tube - A very high quality tube microphone cable.
PSU Schematic - I struggled to find a proper schematic for a u47 PSU. This schematic was suggested to me earlier in this thread, and it’s what I referenced during my build.
Telescoping is a grounding scheme for shielded wires where you ground one end of the shield, but not the other. This helps avoid ground loops. The concept applies to the chassis as well and your grounding scheme is extremely important to avoid noise. Really take the time to think through this part and understand your grounding path. You don’t want a bunch of different paths to ground. Here's a post on the topic that I found quite useful.
View attachment 112907
Resistors and Coupling Caps
I found the following useful in understanding R1, R2 and C2, C3 coupling capacitor values.
Hopefully some of that info ends up being helpful. To finish, here's a few pictures of my completed build.
View attachment 112918
View attachment 112920
View attachment 112915
View attachment 112911
View attachment 112914
View attachment 112923
View attachment 112922
Could you possibly let me know what exact PCB's you went with? Also, I reached out to Dan, a very nice gentlemen. Unfortunately, I was left with more questions than answers. I mentioned that I was trying to emulate your build. I shared a link to this post. However, without knowing the exact components it's pretty much a shot in the dark
so far I have:
1 - Haufe BV08 (Vox-O-Rama)
I want to purchase the VF14M from Phaedrus
Thanks in advance!!
Understood, thanks again for your very informative postsAssuming you're using the Phaedrus, I'd go with the this PCB kit. You'll just be using the PSU PCB, not the mic PCB. I'd suggest the Analog Vibes PSU chassis as well to minimize fabrication. Dan's mic body comes with a PCB that doubles as a transformer mount. I'm pretty sure his version for the AMI BV8Classic would be compatible with the Haufe that your purchased.
As for mine, it's all custom. I designed a custom turret board instead of a PCB for the PSU. The microphone itself is pretty custom as well. I had a bracket milled for the transformer mount and I fabricated custom brackets to side-mount the little turret PCBs. Those turret PCBs are custom as well; I had them manufactured by JLC PCB. There's a reason this project took me like 3 years. I'd strongly suggest not following my lead. lol.