D-EF47 Tribute To Oliver Archut U47 Build Thread.

[soliloqueen]

What is the beef with Mic & Mod?

selling off the shelf parts at 2-5x markups with work scraped from this site without credit. Borderline scam. Outrageous lies about part origin. If you want basically anything M&M sells, make a WTB thread in sales or contact chunger, or anyone else who does business with the same companies at volume. Even Dachman, who has similar issues, has more fair pricing than M&M. He's got literally the same parts up for less than half that price! Even that's still a bit high.

 

[mrgrooves666]

Finishing up this great mic project, thanks Dan and Mr Archut up there. Powering up the PSU without mic connected or dummy load, I get B+ 105, H+ 30V, If I move the polar pattern switch to the other position, B+ goes to the roof 250+ or so. I've read the thread and I get some sense this might be normal and that I need to get the mic plugged or use dummy load 150K 1/2 watt for B+ and 30 ohm 4 watt for heater, to get more proper readings?
I went through every component value, orientation (for those that matter) and it seems I have everything up to spec. I don't have those resistors handy, so its either plug the mic and see if it explodes or somethin' or wait a couple of days for resistors...?

 

[Purplenoise]

Finishing up this great mic project, thanks Dan and Mr Archut up there. Powering up the PSU without mic connected or dummy load, I get B+ 105, H+ 30V, If I move the polar pattern switch to the other position, B+ goes to the roof 250+ or so. I've read the thread and I get some sense this might be normal and that I need to get the mic plugged or use dummy load 150K 1/2 watt for B+ and 30 ohm 4 watt for heater, to get more proper readings?
I went through every component value, orientation (for those that matter) and it seems I have everything up to spec. I don't have those resistors handy, so its either plug the mic and see if it explodes or somethin' or wait a couple of days for resistors...?

It’s not safe to have the psu on without a load…and in order to have proper readings you need of course a proper load or the mic connected. Wait for the right resistors

 

[mrgrooves666]

Well got anxious and plugged the mic. I was able to dial B+105V and Heater 5.05V nicely. Mic is finished and sounding gorgeous

 

[wstratton]

I decided to sell my trusty D-EF47 in pursuit of building another microphone, and I put together a quick demo video, in case anyone reading this thread in the future wants to hear what one idiosyncratic variation of this mic sounds like:

If anyone is interested in purchasing it, feel free to send me a message.

 

[innercityman]

Hi all,

I've finished building my second D-EF47 PSU and did a rough calibration inserting dummy loads, and I can't get 105VDC on B+ with trimmer fully clockwise, the most I can get is 102V no more. I guess it comes from my power transformer which has a 200VAC secondary. So should I change the trimmer resistor with a lower value ? Or should I change the power trafo ?


Thanks for your advices

 

[innercityman]

Forgot to say that I used a 150K resistor for B+ dummy load so maybe with the mic plugged in it will be fine. Otherwise, I suppose that if the trimmer is fully clockwise there is no resistance so changing it for another value will change nothing I guess.

 

[innercityman]

Mic plugged in today and no problem to get 105Vdc. I guess a 150k resistor is probably a little too much for B+ dummy load

 

[TLRT]

Hi all,

I've finished building my second D-EF47 PSU and did a rough calibration inserting dummy loads, and I can't get 105VDC on B+ with trimmer fully clockwise, the most I can get is 102V no more. I guess it comes from my power transformer which has a 200VAC secondary. So should I change the trimmer resistor with a lower value ? Or should I change the power trafo ?


Thanks for your advice

Lower the 2x20k B+ resistors to 12k

 

[mihi_fuchs]

Hi all,

I'd have one question concerning the PSU. If I'm in Europe I have 230V AC from the socket - do I still need the Toroidal Transformer? As it would actually transform 230V AC to 230V AC?

Probably that's a stupid question, but thanks in advance already for any help ...

Looking forward to the first tryout of the mic,
Thanks a lot for the design!

Best regards
michael

 

[rock soderstrom]

This question comes up every now and then. The answer is - don't do it!
It is dangerous not to have a galavanic separation between the electric device and the mains voltage.
It threatens the life of the user and is forbidden (in at least Europe). If it comes to an incident you will be fully liable for it.

 

[mihi_fuchs]

This question comes up every now and then. The answer is - don't do it!
It is dangerous not to have a galavanic separation between the electric device and the mains voltage.
It threatens the life of the user and is forbidden in (at least) Europe. If it comes to an incident you will be fully liable for it.

thanks a lot for the quick reply. very much appreciated!

 

[robinhuntmusic]

HI Guys,

I just completed this project. Have to say, am super happy with the sound. Really nice texture and dead silent! I will put it through its paces with proper vocal recordings. Thanks to @poctop for the great PCB, @wrentema for his insights and help. My dad for the (electronic) guardian angel he is and of course Oliver...<3

I went roughly the same way wrentema did. The body I got from Aliexpress. Well build and finished. From the inside a bit simple though. I had to be a bit creative getting the pcb in there and make it tight. The t47 transformer I got from AML, I bought some nos Telefunken EF800's and the Blueline M7 capsule from Thiersch.

The shockmount I also got from Tab Funkenwerk. For the clips to close the spider I had to made a solution as the Aliexpress body is a bit thicker. I fixed this with simple iron wire with a shrink tube over it

Some difficulties I had with the build was the PSU, I bought the beautiful PSU housing from Tab Funkenwerk but it was made for an original point to point wiring I guess (?) there was a metal sheet in there with holes for caps or something. I had to put the multitool to use and get it out. Then I had to arrange the custom big screened Torroid (from audiophonics), choke and pcb in a way it made sense. I made sure the 5W 50 Ohm Heater voltage potmeter made contact with the housing so that it could transfer it's heat easier.

I made sure the grounding was tight: 1 star point in the PSU where the powersocket ground is connected to, the screen of the torroid, the housing and the 7 pin XLR ground. The 3 pin XLR I connected straight to the 7 pin. In the mic I made sure there was one point where I connected the housing to the pcb. Of the PSU-PCB I did not connect the 0V line. (as this is ground and I thought it better to use just 1 connection from the pcb to the ground which is connection "7". On both the XLR plugs I connected the 'sleeve' with the ground pin.

Another difficulty I had was calibrating: With the 30 Ohm test-load resistor I never got get the H+ to 5.05v. It was always too high (lowest I got was around 6.5V). With the mic plugged in this was easier. I made sure to let the mic heat up for about an hour or so to make final adjustments, then I got easily to 105V on B+ and 5.05V on H+ (here with 240V so all resistor values are cool). It takes a serious amount of time to stabilize. The 150k resistor worked well to get into the ballpark.

I was pretty secure with making sure the 7 pin XLR connector had the right signals / voltages going over them:

1: Audio -
2: Audio +
3: Extra ground.
4: H+ (the thick wire in my Sommer cable Octave Tube)
5: B+
6: Pattern
7: Ground (the other thick wire in the Sommer tube cable)

Other info:

The little polar pattern badge I got from Ebay (opus1374), switches and lights from Conrad, The Mic case from [email protected]

Thats about it. Can't wait to record Thanks everybody for their info and insights!

 

[AB_Music]

Hi guys, I've finished my U47 mic build with a Thiersch M7 capsul and EF800 tube...I've also built my own psu and cable. The Mic works and sounds great and all voltages are fine but I have a problem with a ground hum. It starts as soon as I plug in the power cable connected to the mains power...even if the psu is turned off. It disappears when I disconnect the mic from the psu.
I've also done a few checks to locate the problem...here is what I've checked.
- checked all connections to ground with multimeter (they all seem to be fine)
- connected an additional ground from mic body to psu (the hum gets a little louder)
- removed ground from xlr out (the hum gets much louder)
- disconnect mic from psu (hum disappears)
- manually connected pin 7 (ground) on the cable with with A+ or A- (with cable connected to psu, no mic connected) produces the same hum as the connected microphone
- maybe good to know...I've soldered the ground wire and the shield of the cable both to pin 7

Any idea what could be the problem and how to solve it?

 

[mrgrooves666]

How is the layout in your PSU? My first attempt was in a pretty tight case, and I had hum. After breaking my head revising and trying different grounding scenarios I concluded it was interference from traffos to pcb. Moved to a bigger case, placed pcb to the xlr side, traffos and choke to power side, scenario as suggested by Dany and hum was gone for good.

 

[TillM]

Try this grounding scheme. It worked perfect for my ef800 build.

 

[AB_Music]

How is the layout in your PSU? My first attempt was in a pretty tight case, and I had hum. After breaking my head revising and trying different grounding scenarios I concluded it was interference from traffos to pcb. Moved to a bigger case, placed pcb to the xlr side, traffos and choke to power side, scenario as suggested by Dany and hum was gone for good.

Layout is relatively tight but xlr‘s and pcb is on one side and all trafos, choke and power + switches on the other side. I‘ve also removed all trafos and choke from the case and placed it as far away as possible from each other. No difference….hum was stil there.

 

[AB_Music]

Try this grounding scheme. It worked perfect for my ef800 build.
View attachment 94571

Alright…that looks smart. Have to get a DPDT switch, but I will definitely try this. Thanks man

 

[TillM]

I don’t needed the switch. Just try it.

 

[TillM]

But please check with a DMM the ground connection.