The Ultimate DIY U47 - Build Thread (And some PSU questions)

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StormsofVogue

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Yes Dan's AKA Poctop's bodies are the best I know of. The Phaedrus Audio tube solutions are excellent IMO and their customer service is quite good.

I have used the Phaedrus solution in multiple builds and I am quite happy with the result. The EF800 is IMO the best actual vacuum tube alternative to the VF14K. The EF800 does require filament voltage and obviously is a totally different socket. One nice thing about the Phaedrus approach is that if you ever stumble across an actual usable (now unobtainium) VF14K you can just pop it in the mic.

The phaedrus is not the only FET based solution on the market for VF14 replacement. Andreas Grosser makes one but at last inquiry would not sell it unless you let him install it in the mic. Their are also Tube solutions by Telefunken, and Saturn sound are made I only mention them as they are there IMO these are not the answer.

Two notes that I noticed in your build photos. In your PSU the resistors you are using in the filter circuit are they the right wattage they look rather small to me. They get very warm. I myself use wire wound types in this area and use a case that acts as a heat sink. The drop down resistor that gives the filament voltage gets warm and needs to be properly installed so that its heat is dissipated into the mic body. The Phaedrus VF14M does not like excessive heat. I built a copy that is overstuffed with vintage parts and had to move the drop down resistor into the PSU as I could no longer get the heat to a low enough level to not cause problems. My website has some info in the blog section

Accopean power supplies makes a regulated UL listed PSU that I use and it works great. Yes I know part of the sound is down to the unregulated nature of the supply but I opted for safety and consistent voltage and I have not noticed a truly tangible sonic difference. If anything IMO the regulated supply makes for a bit more presence in the sound.



Glad to hear more praise of the Phaedrus tube!

Yeah, I'll be using 5w resistors. If you're referring to the 4th picture down, that just an example of what I was thinking for how I might build the PCB.

Good to know about the heat issue. Dan uses these 10w HS10 style heat-sinked resistors in his builds and my mic body even comes with a block pre-drilled and tapped for one. The issue I'm having is that I can only find a 1.5k. In fact, I've noticed Dan has a 1.5k in his examples. No idea how he's making that work or what tube he's even using. I may need to just email him and ask.

Oh man. That regulated PSU is really tempting. I like the idea of building my own, but I also like the idea of a regulated and consistent power supply. Which model did you purchase? Since it's regulated, I'm assuming I don't have to worry about the volage spec changing under load, so 105v?
 

Andresound

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Slightly off topic…, but has anyone used the 3Cm tube in a 47 style build? I have currently inherited a few and looking to do a 47 style project
 

TLRT

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I'm making those vintage style PSU's for my clones and original u47's(all passive RLC style, voltage adjustment on front panel):
 

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There will never be an "ultimate" U47 clone, but using a high quality body, head, transformer, tube and most important capsule is an inevitable start. In my experience cheap parts is a bad investment. To me M7 work better than K47. Unregulated PSU and carbon film resistors helps getting a few percentage closer to the "right" sound. With only three capacitors you can easily experiment with different types and brands.
When you use another tube and circuit I actually don't think it's a true clone, rather U47 inspired. I think the original design with the simple PSU and single voltage is what makes U47 special.

I've repaired and installed Phaedrus in two vintage U47 and compared them directly to a few with VF14 and VF14M. To me the the "frequency response" sounds right but dynamically I can hear the solid state qualities which not necessary is bad. It has less "swell" and a tighter bass. I've only tested/analyzed those microphones and not really used them in recording situations meant for a final product. I think that aspect is really important. A microphone that sounds good is not always a great tool in the studio.

I've built, heard and worked with many U47 "clones" with EF12. They are not in any way direct replacements of an original since EF12 have a different tone than VF14 but they have the right dynamic qualities, sound really nice and work superbly in the studio. I've never heard one with EF800. I'd love hear Telefunken USA and both of Grossers VF14 substitutes.
 

StormsofVogue

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Slightly off topic…, but has anyone used the 3Cm tube in a 47 style build? I have currently inherited a few and looking to do a 47 style project

I've never heard of that tube. Google didn't get me anywhere either. As you can tell by reading this thread, deviating from an established circuit even a little is not simple. If you want to do a U47 build, I'd suggest getting Dan's EF-800 PCB's and starting there. I wouldn't bother with the tube you have.

I'm making those vintage style PSU's for my clones and original u47's(all passive RLC style, voltage adjustment on front panel):

Beautiful!

There will never be an "ultimate" U47 clone, but using a high quality body, head, transformer, tube and most important capsule is an inevitable start. In my experience cheap parts is a bad investment. To me M7 work better than K47. Unregulated PSU and carbon film resistors helps getting a few percentage closer to the "right" sound. With only three capacitors you can easily experiment with different types and brands.
When you use another tube and circuit I actually don't think it's a true clone, rather U47 inspired. I think the original design with the simple PSU and single voltage is what makes U47 special.

I've repaired and installed Phaedrus in two vintage U47 and compared them directly to a few with VF14 and VF14M. To me the the "frequency response" sounds right but dynamically I can hear the solid state qualities which not necessary is bad. It has less "swell" and a tighter bass. I've only tested/analyzed those microphones and not really used them in recording situations meant for a final product. I think that aspect is really important. A microphone that sounds good is not always a great tool in the studio.

I've built, heard and worked with many U47 "clones" with EF12. They are not in any way direct replacements of an original since EF12 have a different tone than VF14 but they have the right dynamic qualities, sound really nice and work superbly in the studio. I've never heard one with EF800. I'd love hear Telefunken USA and both of Grossers VF14 substitutes.

Yeah, but "ultimate" makes for a better thread title. ;) Also, while "ultimate" may be subjective, there is indeed quite vast difference between a low-grade clone and a high-end one. I'm trying to build one that doesn't just work, but also looks like art, both inside and out... we'll see how that goes.

I agree, U47 inspired is a good description.

Interesting take on the Phaedrus. Given their claims on the accuracy of the frequency response (which I assumed were probably correct), the tube dynamics are exactly what I might have expected to be missing from such a device.
 

Recording Engineer

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I have the Phaedrus, new Telefunken, and a socketed 5906 from Barbaric Amplification. I can put them in 2 different 47-types; one with a Thiersch M7 Redline in an AMI body and an AMI supply, the other in a Beesneez body with a Barbaric supply -inspired by AMI, Neumann K47, both with AMI BV08s. I find the Phaedrus more open and modern, the 5906 more rolled-off and vintage. I still have played with the Telefunken enough. I don’t have an EF800 version. Barbaric was doing that before doing the socketed-5906.

I’ve got all the BV08s to try (other than Beesneez that I still need to grab). Whenever I get to it, my next 47-project will be trying them all. I’ve already got enough of all the parts for a few more finished 47s.

Not a C3m (maybe that’s what you meant), but once Mark at Samar Audio ever gets to making the choke for me, I have a C3g for a Ronin Applied Science Pegasus -inspired mic!
 
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StormsofVogue

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Alright guys! After about 30 hours of research, decision making, and part hunting, I just placed my Mouser part order. I'm gonna do a custom turret board for the PSU, but I'll lay it all out in KiCad first. I've got an AMI BV8R on the way as well.

I really appreciate everyone's input! I wouldn't have been able to get to this point without it. I'll keep this thread updated as I make progress.

I have the Phaedrus, new Telefunken, and a socketed 5906 from Barbaric Amplification. I can put them in 2 different 47-types; one with a Thiersch M7 Redline in an AMI body and an AMI supply, the other in a Beesneez body with a Barbaric supply -inspired by AMI, Neumann K47, both with AMI BV08s. I find the Phaedrus more open and modern, the 5906 more rolled-off and vintage. I still have played with the Telefunken enough. I don’t have an EF800 version. Barbaric was doing that before doing the socketed-5906.

I’ve got all the BV08s to try (other than Beesneez that I still need to grab). Whenever I get to it, my next 47-project will be trying them all. I’ve already got enough of all the parts for a few more finished 47s.

Not a C3m (maybe that’s what you meant), but once Mark at Samar Audio ever gets to making the choke for me, I have a C3g for a Ronin Applied Science Pegasus -inspired mic!

Random question. How is the fit and finish of your Beesneez body? I purchased one back at the peak of the pandemic and the unit seemed like it was a B-stock. All the large chrome parts had small dents on them and some of the non-threaded mount holes were slightly oversized and non-concentric. I initially tried to get a replacement, but shipping to and from Australia took months due to the pandemic. I struggled to get consistent communication with Ben. If there were any production or pandemic related issues on his end, he didn't say so (although it's quite possible there were). After 6 months I ultimately had to get a refund. I really liked the body. Finish issues aside, it was built like a tank. I'd buy again if I knew I could get one in good shape.
 

Recording Engineer

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My Beesneez 60mm body (the version before they went to the connector/mount combo version), 51mm body, and M49/50 body pair are all absolutely perfect; fit and finish. Beesneez has been through some trying and extremely devastating periods though, so who knows what went on with your body during this pandemic time. I’m waiting for a pair of BV12s from them that they said would be very-quick when I ordered them. But, whatever, I’m extremely-patient to a fault and they’ve always always always come through for me eventually.

And I will eventually be ordering another of their 47 bodies for that Pegasus-inspired one; as it deserves the best I can get since I fell in love with the real one after using one quite a few times and absolutely kick myself that I didn’t preorder one of the ten ever made for extremely-reasonable money at the time. But, that’s how it’s been for a number of things now. Oh well. I still haven’t learned.
 

StormsofVogue

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My Beesneez 60mm body (the version before they went to the connector/mount combo version), 51mm body, and M49/50 body pair are all absolutely perfect; fit and finish. Beesneez has been through some trying and extremely devastating periods though, so who knows what went on with your body during this pandemic time. I’m waiting for a pair of BV12s from them that they said would be very-quick when I ordered them. But, whatever, I’m extremely-patient to a fault and they’ve always always always come through for me eventually.

And I will eventually be ordering another of their 47 bodies for that Pegasus-inspired one; as it deserves the best I can get since I fell in love with the real one after using one quite a few times and absolutely kick myself that I didn’t preorder one of the ten ever made for extremely-reasonable money at the time. But, that’s how it’s been for a number of things now. Oh well. I still haven’t learned.

Good to hear. I may try to order one again at some point. I just wasn't willing to wait passed the 6 month mark (2.5 of which were shipping) since my PayPal protection expired after that. Fingers crossed I get a good one next time.

That Pegasus mic sounds like a super interesting project. I assume the choke you mentioned earlier is the custom toroidal transformer for the microphone? I'm curious as to how you were able to get the transformer specs, and schematic info... or are you just building something of similar design theory to the Pegasus?
 

Recording Engineer

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The choke is used in place of the plate resistor. The toroid you’re thinking of is actually the output transformer. Mark actually designed and built the later, and he has extras laying around, so I picked that up from him already. The former was designed and built by someone else, so Mark is just doing what he would do.

As for a schematic, no, but based on pictures and Dimitri’s details, posted here for example, I’m just going for something inspired-by:
 
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StormsofVogue

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The choke is used in place of the plate resistor. The toroid you’re thinking of is actually the output transformer. Mark actually designed and built the later, and he has extras laying around, so I picked that up from him already. The former was designed and built by someone else, so Mark is just doing what he would do.

As for a schematic, no, but based on pictures and Dimitri’s details, posted here for example, I’m just going for something inspired-by:

Super interesting. That's gonna be quite a mic!
 
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I've never heard of that tube. Google didn't get me anywhere either. As you can tell by reading this thread, deviating from an established circuit even a little is not simple. If you want to do a U47 build, I'd suggest getting Dan's EF-800 PCB's and starting there. I wouldn't bother with the tube you have.



Beautiful!



Yeah, but "ultimate" makes for a better thread title. ;) Also, while "ultimate" may be subjective, there is indeed quite vast difference between a low-grade clone and a high-end one. I'm trying to build one that doesn't just work, but also looks like art, both inside and out... we'll see how that goes.

I agree, U47 inspired is a good description.

Interesting take on the Phaedrus. Given their claims on the accuracy of the frequency response (which I assumed were probably correct), the tube dynamics are exactly what I might have expected to be missing from such a device.
Hehe, with all the DIY U47 threads out there it's important to have an appealing title. Actually for years I have myself done a lot of work to find out how to build the "ultimate" U47, U67, M49, C12 etc. If you are stubborn and ready to spend some money I'm sure you will end up with a great microphone. There are a lot of details that influence the final result and that's both the charm and frustration when building microphones. It took me five years between my first working microphone and my first microphone that sounded really good. That was a TLM49 to M49 conversion with AC701 and Neumann K47. But I always try to push things to the limit and I have modified that microphone a lot of times since then...

The last years I've had the advantage to hear quite a lot of vintage originals. That has helped me much to raise the quality of my own builds.

Getting back to U47 I'm currently building drop in replacements with a single 408a and I'm getting really promising results. The 408a solution has been discussed (and discarded) many times and noise seem to be a big issue for most. I have 10 Ericsson and 9 are noisy, all of them microphonic. I have two Philips that were selected when I got them, low noise and sound really good but microphonic. I have five Western Electric that all have acceptable noise levels. Two of them are not microphonic at all and one of those sound really close to VF14 when I test with acoustic guitar. My initial aim was to have a drop in replacement to offer when I repair U47 but now I'm considering rebuilding one of my DIY 47 with EF12.
 

Pip

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I appreciate your attention to detail and the desire to do it all from scratch my early builds adhered to this approach. I started using the Accopean PSU because of safety concerns and ease of use.

Also check out Zayance in White Pages


 

Pip

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Hehe, with all the DIY U47 threads out there it's important to have an appealing title. Actually for years I have myself done a lot of work to find out how to build the "ultimate" U47, U67, M49, C12 etc. If you are stubborn and ready to spend some money I'm sure you will end up with a great microphone. There are a lot of details that influence the final result and that's both the charm and frustration when building microphones. It took me five years between my first working microphone and my first microphone that sounded really good. That was a TLM49 to M49 conversion with AC701 and Neumann K47. But I always try to push things to the limit and I have modified that microphone a lot of times since then...

The last years I've had the advantage to hear quite a lot of vintage originals. That has helped me much to raise the quality of my own builds.

Getting back to U47 I'm currently building drop in replacements with a single 408a and I'm getting really promising results. The 408a solution has been discussed (and discarded) many times and noise seem to be a big issue for most. I have 10 Ericsson and 9 are noisy, all of them microphonic. I have two Philips that were selected when I got them, low noise and sound really good but microphonic. I have five Western Electric that all have acceptable noise levels. Two of them are not microphonic at all and one of those sound really close to VF14 when I test with acoustic guitar. My initial aim was to have a drop in replacement to offer when I repair U47 but now I'm considering rebuilding one of my DIY 47 with EF12.
I believe so is Telefunken and Saturn Sound among others, that being said I have written about my feelings regarding the noise issues of the 407a and 408a approaches. IMO they just don't have the reliability that is necessary for a microphone impedance circuit. They were never a low noise option to begin with, I believe they were used in Telco Circuits and they also do not have, IMO, consistent sonic qualities, the sound varies greatly between types (JAN) and manufacturers also country of manufacture effects results I have noticed.

My favorite for the two tube 408a method is this type; Philips MINIWATT TS62 / 408a / 6028.
They are the most musical sounding of the lot and quiet, the downside they are very microphonic so they need damping. They are also expensive.
 

Purplenoise

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The closest I have gotten to the “u47” sound was using the 13cw4 nuvistor. I have build two ptp 47s, one with all proper components but different bias for the nuvistor suggested by Andreas Grosser and Moby and the other one with the Neumann bias but bv11 transformer ( David Bock suggestion)
 

StormsofVogue

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I appreciate your attention to detail and the desire to do it all from scratch my early builds adhered to this approach. I started using the Accopean PSU because of safety concerns and ease of use.

Also check out Zayance in White Pages



I was thinking I would build out a custom, more traditional PSU for now, and possibly put together an Accopean based PSU at a later date if I felt I wanted the added safety and voltage stability for regular use.

Thanks for that link to the MK47 PSU doc! I could only find that one image of the MK47 schematic.

I also grabbed a cheap variac. Figured it would be useful for the initial build process, and for manually keeping a consistent wall voltage for the mic when it's eventually put into action. I'm gonna put a more accurate digital volage readout on it as outlined in this tutorial.

variac.jpg
 

mhelin

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Couldn't you just use PV cell(s) with a LED(s) to use the B+ supply as heater supply for regular 4-6.3V heaters, stuffed with a glass tube inside a metal (or plastic) bottle (VF14 kind of with the 8-pin base).
 
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I believe so is Telefunken and Saturn Sound among others, that being said I have written about my feelings regarding the noise issues of the 407a and 408a approaches. IMO they just don't have the reliability that is necessary for a microphone impedance circuit. They were never a low noise option to begin with, I believe they were used in Telco Circuits and they also do not have, IMO, consistent sonic qualities, the sound varies greatly between types (JAN) and manufacturers also country of manufacture effects results I have noticed.

My favorite for the two tube 408a method is this type; Philips MINIWATT TS62 / 408a / 6028.
They are the most musical sounding of the lot and quiet, the downside they are very microphonic so they need damping. They are also expensive.
Thanks for your input. The other day I ordered a couple of those Philips Miniwatt TS62, will be very interesting to hear them. I can clearly hear the differences between the manufacturers and also individual tubes. I have not heard enough healthy VF14 to tell if the individual tubes sound different but it's clear that a worn out VF14 that hardly reaches over 30V at the anode doesn't sound as intended. Noisy (noisier than most 408a), hard mid and bass shy. I've only heard 408a in original U47's and if you for a while let go of how the tube "should" sound you can hear that a selected 408a makes a great microphone. I'm a bit worried about the reliability in the long term because the microphone gets really hot.

Until someone comes up with something better I will use this tube (as I said before I haven't heard Grosser and Telefunken USA and I can't buy them). My VF14M is currently getting a bit of rest and I will see how it works in the studio with 408a in my U47. I'm definitely converting my EF12 DIY in the near future.

Does anybody know the voltages at the anode, cathode and the filament in the Telefunken USA U47?
 

shabtek

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there was discussion maybe here and definitely at guru fora about 'thermal biasing'--part of the sound of the original comes from the heat; the mic circuit system performs as it does due in part to the components being hot...
 
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