Advice for building a U47 clone

[Eike]

Hi folks,
I'm more and more interested in building an U47 Clone. I helped a friend building a U47 kit and that's how I first got into contact with the subject. Financial resources are limited (I know, I know..), but after months of G.A.S. I need it.

My idea was to use these parts:
Alibaba U47 body
Arienne Audio or Maiku K47-Capsule
UTM 0547 Transformer
Gyraf G7 schematic + Power supply
EF86+socket
Small parts from mouser+donaudio

One big question is the microphone PCB. The G7 Gerber file is made for the Lundahl Transformer and I need a solution to fit the UTM transformer into the body. What I expect is that many people had the same thoughts as I had and already made solutions. But the sheer amount of information makes it hard to find the ones I need. Any hints?

Best
Eike

 

[Khron]

How big of a hurry are you in? And would you have something against using a t.Bone SCT700 / SCT2000 as a donor body?

 

[garp]

Please forget the Maiku, Heisermann or any other "K47" clones and go for the Arienne, you will not regret it, the capsule is one crucial element in this build. The gyraf pcb is cool but maybe a bit "far" from the original design. Personnaly i went to the double 408a solution and was tempted to do a ef800 "archut" version. Long long time ago I made 3 clones, two with Dale Ullan M7's and one with K47 that i recently updated with a K47 from Arienne and despite my affection for the M7 (i also have several original neumann and gefell with M7) , this one is now my favorite. Another important point is the power supply that i choosed to make "point to point" because i ifound it easier to build and tweak. Last thing, if you are planning to have an intensive use of this mic, avoid those ugly and undersized 7 pin XLR and prefer 7 pins grosstuchel or binder 23 series (cheaper) much more designed to withstand the voltages and intensities involved here. You can find binder 23 for nearly the price of "hi end" 7 pins XLR's. Also invest in a good cable (Old Belden's are gems and will last forever but gotham, mogami made good ones )

 

[Eike]

Alright! I had a look at soliloqueens Thread- she makes the Arienne capsules, right? So I will go with them. Regarding the schematics it seems I have to dig deeper.. Hard for somebody who is not really into electronics but can solder really well.
Yeah, I already hate the 5 pin XLRs mostly used on DMX cables. Using the Binder 7 pin connectors is a good idea, but I have to find the right parts. Maybe this is an option when the mic prooves it works. And I'm totally with you, no shitty cables.

 

[garp]

I used this serie but with 9 pins

 

[garp]

The cable and PSU are so important that i always begin by this job in a build. I also try to avoid arbitrary solutions that i will regret later, then once something is done, it's done and so i am sure that this part will not cause me problems later ! There are loads of solutions to properly mount a transformer, i sometimes choose to build a separate board to fit the transformer appart from the rest of the circuit like here : (should i mention that moby's transformers are dope ?)

 

[Eike]

I will do that! A stable power supply is a must.

Could I go with that? https://vintagemicrophonepcbkit.com/D-EF47.html
Am I right that this schematic uses a relay to disconnect the back capsule to switch between omni and cardioid? Is it possible to go without the relay and mount a switch in the original position?

I heard a lot of people telling nice stuff about moby transformers. Is the difference between UTM and Moby so big?

 

[tomas.borgstrom]

I would go for EF12, EF14 or EF800. I prefer M7 in U47. Thiersch red line or 3U Audio are my current recommendations. Arienne K47 flat is another alternative. Moby is great, AMI is high quality as well. I have no experience with UTM. Some prefer FAB. I will soon test it myself. Not so much info from DIY:ers when you search.
The circiut is so simple that a printed PCB is not really necessary. You can solder many resistors on the tube socket or just use an experiment PCB.

 

[Delta Sigma]

EF800s or EF802s are relatively affordable, the circuit is easy to build and troubleshoot, and it sounds fine. You might prefer a different tube, but a high quality capsule, Moby iron, and a decent mic body will get you most of the way to what you want. To me, the tube is less important than those three. Especially the capsule.

A good case for the power supply will make your life easier. Dany's EF47 PCB kit includes the PSU PCB.

In general though, mics are hard to build without electronics knowledge. One bad ground can make your life miserable. Might be a good opportunity to learn. Not sure anyone else agrees, but I don't see DIY as a way to save money. I see it as a way to learn, and a way to make the mic sound exactly how I want it to sound. It's a lot cheaper to buy a Warm Audio mic. Maybe even cheaper to buy a Beesneez or Flea, depending on how many component orders you put in trying to tweak the sound.

 

[Delta Sigma]

I found it easy to modify the circuit for variable patterns and use a relay or switch for "cardioid only". Switch vs relay doesn't matter too much. Easy change to make.

Also, why U47?

My DIY U67 is (to me) my most versatile vocal mic and a great instrument mic. My DIY C12 (to me) is my most versatile instrument mic and a great vocal mic. My favourite vocal mic is my DIY M49b with a Beesneez M7. My DIY EF-U47 (Arienne Flat K47, previously Beesneez K7) is great, and has a certain front of mix pop sound, but it doesn't excel as often as the M49 and isn't as versatile as the U67/C12.

 

[mihi_fuchs]

I will do that! A stable power supply is a must.

Could I go with that? https://vintagemicrophonepcbkit.com/D-EF47.html
Am I right that this schematic uses a relay to disconnect the back capsule to switch between omni and cardioid? Is it possible to go without the relay and mount a switch in the original position?

I heard a lot of people telling nice stuff about moby transformers. Is the difference between UTM and Moby so big?

Dany's PCBs work just fine. If you use additionally a cathode bypass cap you can actually even work with the regulated PSUs here based on LM3xx regulators.
I used UTM a lot. I am very happy with them. I think I even have somewhere a comparison of those to the 3u audio transformers (some white noise files). I'm not sure if they are in the ElaM251 or C12 thread of mine - check - if you need the audio I can provide it via dropbox or google drive.

The relay is exactly as you pointed out for the capsule diaphragm's connection. I don't see a point why you cannot replace it by a switch. Just connect the switch to the apropriate pin holes of the relay on your PCB.
If you use a regulated PSU you can also use the heater voltage for the relay and use a 6V relay.

I guess you know already, but none of the mentioned PCBs/schematics is really a clone of the U47. they use different tubes and the G7 is a (undoubtfully ver nice) mixture of three different microphone designs. But that info is clearly outlined on gyraf's homepage.

I have made a PCB for one of the U47-like mics with the cathode bypass cap and UTM transformer footprint. But none available at the moment. Guess by July could be ready (depending on my motivation for spending money on them ;-) which depends again on the negotiations with my wife ... hahaha). You can check the pdf file here: https://groupdiy.com/threads/u67-psu-from-standard-tube-microphone-psu-for-sct800.87319/post-1152843

Hope that helped, just post if you have more questions ...
Best regards
Michael

 

[elmolemon]

How big of a hurry are you in? And would you have something against using a t.Bone SCT700 / SCT2000 as a donor body?

Wow, are there even more mic projects in the pipeline? Do you plan to also offer a U47 style PCB?

 

[Khron]

Wow, are there even more mic projects in the pipeline? Do you plan to also offer a U47 style PCB?

Yes and no... Some tube stuff yes, but not quite so straight-forward.

What even is "U47 style" though, by the way? Fixed bias triode? Or the no-separate-heater-supply aspect? Or..???

 

[elmolemon]

Yes and no... Some tube stuff yes, but not quite so straight-forward.

What even is "U47 style" though, by the way? Fixed bias triode? Or the no-separate-heater-supply aspect? Or..???

Great! I was already looking forward to your announced mic projects. Additional tube stuff sounds interesting, too.

Re U47 style: I’d love to be able to discuss circuits on a technical level, but I’m new to DIY still trying to learn and understand basics. As “true” U47 clones can hardly be built due to the VF14 steel tube shortage, I would imagine a “U47 style” mic to approach the classic “larger than life” sound with an alternative tube circuit, while still going with a M7/K47 capsule, a BV-08 transformer and a big mic body / head. Beyond that you’re the expert for sure.

 

[tomas.borgstrom]

Also, why U47?

My DIY U67 is (to me) my most versatile vocal mic and a great instrument mic. My DIY C12 (to me) is my most versatile instrument mic and a great vocal mic. My favourite vocal mic is my DIY M49b with a Beesneez M7. My DIY EF-U47 (Arienne Flat K47, previously Beesneez K7) is great, and has a certain front of mix pop sound, but it doesn't excel as often as the M49 and isn't as versatile as the U67/C12.

I agree!

 

[Eike]

How big of a hurry are you in? And would you have something against using a t.Bone SCT700 / SCT2000 as a donor body?

I'm not in a hurry!

EF800s or EF802s are relatively affordable, the circuit is easy to build and troubleshoot, and it sounds fine. You might prefer a different tube, but a high quality capsule, Moby iron, and a decent mic body will get you most of the way to what you want. To me, the tube is less important than those three. Especially the capsule.

A good case for the power supply will make your life easier. Dany's EF47 PCB kit includes the PSU PCB.

In general though, mics are hard to build without electronics knowledge. One bad ground can make your life miserable. Might be a good opportunity to learn. Not sure anyone else agrees, but I don't see DIY as a way to save money. I see it as a way to learn, and a way to make the mic sound exactly how I want it to sound. It's a lot cheaper to buy a Warm Audio mic. Maybe even cheaper to buy a Beesneez or Flea, depending on how many component orders you put in trying to tweak the sound.

I'm totally with you. But the experiences I made told me that building an own mix is worthy investing time and money because the results can be quite stunning! I'd like to build a U47 because of the extensive use in the Beatles era. I currently work on reenacting Beatles stuff for research purposes, and it would be nice to use a U47 for vocals, guitars. A U67 build is planned- but as a stereo pair.

Dany's PCBs work just fine. If you use additionally a cathode bypass cap you can actually even work with the regulated PSUs here based on LM3xx regulators.
I used UTM a lot. I am very happy with them. I think I even have somewhere a comparison of those to the 3u audio transformers (some white noise files). I'm not sure if they are in the ElaM251 or C12 thread of mine - check - if you need the audio I can provide it via dropbox or google drive.

The relay is exactly as you pointed out for the capsule diaphragm's connection. I don't see a point why you cannot replace it by a switch. Just connect the switch to the apropriate pin holes of the relay on your PCB.
If you use a regulated PSU you can also use the heater voltage for the relay and use a 6V relay.

I guess you know already, but none of the mentioned PCBs/schematics is really a clone of the U47. they use different tubes and the G7 is a (undoubtfully ver nice) mixture of three different microphone designs. But that info is clearly outlined on gyraf's homepage.

I have made a PCB for one of the U47-like mics with the cathode bypass cap and UTM transformer footprint. But none available at the moment. Guess by July could be ready (depending on my motivation for spending money on them ;-) which depends again on the negotiations with my wife ... hahaha). You can check the pdf file here: https://groupdiy.com/threads/u67-psu-from-standard-tube-microphone-psu-for-sct800.87319/post-1152843

Hope that helped, just post if you have more questions ...
Best regards
Michael

I know it's not possible to rebuild the U47 because of the lack of V14 tubes. Sounds like we could get in touch later this summer, I'm from Germany, so Austria is not really a problem I like the idea of using an existing power supply, SCT 700/800/2000 are quite easy to get here.

Great! I was already looking forward to your announced mic projects. Additional tube stuff sounds interesting, too.

Re U47 style: I’d love to be able to discuss circuits on a technical level, but I’m new to DIY still trying to learn and understand basics. As “true” U47 clones can hardly be built due to the VF14 steel tube shortage, I would imagine a “U47 style” mic to approach the classic “larger than life” sound with an alternative tube circuit, while still going with a M7/K47 capsule, a BV-08 transformer and a big mic body / head. Beyond that you’re the expert for sure.

I'm also still new in that topic. But what I learned over the past few years is that it's easier to learn something in practice than just thinkering around.

 

[garp]

The moment of you are planning to use another design than the double 408a, the mic will be far from a U47 (different power supply etc ...) all of this will certainly lead to very good tube microphone, maybe better ... but not a U47 clone IMHO (and i have build several ones).

 

[Eike]

The moment of you are planning to use another design than the double 408a, the mic will be far from a U47 (different power supply etc ...) all of this will certainly lead to very good tube microphone, maybe better ... but not a U47 clone IMHO (and i have build several ones).

So the vintagemicrophonepcbkit D47 fits the best? I know Max Kirchners Kits aren't available anymore.

 

[garp]

IMHO ... yes !

 

[ElSmurf]

+1 on most of what's been said here. Dany's EF-47, Arienne flat K47, Moby BV-08. That way you'll probably have more work with the PSU than the mic itself, which is a good thing IMHO. And end up with a killer tube mic.