D-EF47 Tribute To Oliver Archut U47 Build Thread.

[AB_Music]

I posted here a grounding diagram. Make switchable the audio gnd and avoid ground loops. Use stargrounding.

@mrgrooves666 probably means how to protect the capsule with the zeners.
I would also be interested how to do that

 

[mrgrooves666]

yeah yeah, I'm interested for that precisely, got mine dressed up with a vintage neumann k49 that I was lucky to score in mint condition, don't want to fry it or something lol . Any pointers for impementing the zeners to protect the capsule are greatly appreciated

 

[Bonnie1]

@mrgrooves666 probably means how to protect the capsule with the zeners.
I would also be interested how to do that

Highly recommend powering the relay via the filament supply, like it should be.

Regarding grounding issues,
-You mentioned the mic cable shield and Ov are tied together on pin 7. Is the cable shield also connected to the connector chassis on both ends of the cable?

-Inside your PSU, IEC ground pin should be connected to the PSU chassis, as well as Ov. Ideally the resistance between chassis and Ov is the same as your DMM leads resistance. (There's also another grounding schem..., however I don't want to cause confusion)

Hopefully there's enough info. above to get your issues sorted.

-Cheers

 

[TLRT]

Highly recommend powering the relay via the filament supply, like it should be.

Regarding grounding issues,
-You mentioned the mic cable shield and Ov are tied together on pin 7. Is the cable shield also connected to the connector chassis on both ends of the cable?

-Inside your PSU, IEC ground pin should be connected to the PSU chassis, as well as Ov. Ideally the resistance between chassis and Ov is the same as your DMM leads resistance. (There's also another grounding schem..., however I don't want to cause confusion)

Hopefully there's enough info. above to get your issues sorted.

-Cheers

Rs relays are either 12v or 48v for this project so you cannot run from the 5v heaters. Zener calculations are easy guys you need a limiting voltage,and add a loading resistors to gnd, thats all. Use a zener with a bit higher voltage, so it wont add noise when the mic is working properly. Add zener to the pattern 50v too. Problem with this design is that the relay consume equal or more power than the mic tube. Vintage mics derived the pattern from b+, (see c12, or m49 patterns schemos) but there is no consumption at all (capsule needs pAmps maybe)

 

[TillM]

That’s why I chose Dan’s u47 mic kit body, when I build it with ef800 tube.
The relay for the pattern switch is too faulty.

 

[AB_Music]

Highly recommend powering the relay via the filament supply, like it should be.

Regarding grounding issues,
-You mentioned the mic cable shield and Ov are tied together on pin 7. Is the cable shield also connected to the connector chassis on both ends of the cable?

-Inside your PSU, IEC ground pin should be connected to the PSU chassis, as well as Ov. Ideally the resistance between chassis and Ov is the same as your DMM leads resistance. (There's also another grounding schem..., however I don't want to cause confusion)

Hopefully there's enough info. above to get your issues sorted.

-Cheers

I haven‘t changed anything in the design of the provided pcb, so the relay is powered how it was designed. Also don‘t have the electrical knowledge to change it…I can just build these things like a „sort of“ Lego set.

Anyway…yes shield and ground wire of the cable is tied together…they are also both connected to pin 7 and the ground terminal of the 7 pin connector on the psu side…on the mic side the connector has no extra pin for grounding the housing (see pics)…so shield and ground wire are only connected to pin 7 on this side of the cable.

In the psu ground goes to pcb and chassis.
DMM reads good connection for both ground points. But it was my next idea to redo these connections.

 

[robinhuntmusic]

I build it with the cheaper chinese body. Surprisingly well build. Just the insides could be a bit better.

 

[oongbac]

I haven‘t changed anything in the design of the provided pcb, so the relay is powered how it was designed. Also don‘t have the electrical knowledge to change it…I can just build these things like a „sort of“ Lego set.

Anyway…yes shield and ground wire of the cable is tied together…they are also both connected to pin 7 and the ground terminal of the 7 pin connector on the psu side…on the mic side the connector has no extra pin for grounding the housing (see pics)…so shield and ground wire are only connected to pin 7 on this side of the cable.

In the psu ground goes to pcb and chassis.
DMM reads good connection for both ground points. But it was my next idea to redo these connections.

Maybe it's a bit late reply, I had some buzz issue with my first try. After I saw some thread, tried cut shield connection and also cut connection of chassis and connector of PSU side, the buzz was gone. On mic side pin7(cable shield)connected with microphone body. And I also cut ground and shield connection(pin3-7). I'm a newbie for a mic build, so it may not that helpful with your situation, but it worked for me.

Take a look this page.

https://groupdiy.com/threads/neuman...yle-tlm49-conversion-to-m49-b-c.51862/page-14

 

[oongbac]

Hi guys,

I thought I killed the buzz, but as I attached, there's still small buzz(hum) in the background. I set mic preamp gain to 50dB and add some HPF in 80Hz. Preamp and EQ is AML ez1073. In this setting my normal speaking voice goes -6~-1dBFS.

I can remove this with Izotope RX without defects(I think), but it's a bit annoying.

Is this acceptable? or should I do something to eliminate this background noise.

Please leave comments about it.
View attachment Background noise.wav

 

[oongbac]

I applied @TillM's grounding scheme.

Removed 0v to chassis connection, connect pin7(mic, shield)-pin3(PSU, chassis) / pin3(mic)-pin7(PSU) and hum gets smaller.

I think I've got the best result by far. I attached noise profile. You can see some differences above 1KHz. Picture in the right is after change. Same preamp and EQ setting with above.

I still can hear little buzz anyway...

View attachment noise test01.wav

 

[oongbac]

Maybe I tested in a bit extreme environment. Set my preamp gain to 35, the background noise is barely noticeable. I think I can stop fixing now. Of course keep trying remove little noise, but I think it can be from my wall power. My place is quite old house.

Thank you for the sharing your knowledge. Ground scheme from @TillM and @TLRT is definitely working. Really appreciate.

Here's a sample in more realistic usage. I didn't do any noise suppression.

View attachment noise test_1.wav

 

[oongbac]

Sorry for the too many replies, but for less experienced builders like me, please let me share my case.

I used smaller one than the usual toggle switch for a power switch, because of spacing.

I thought it can be faulty, so I changed that one to bigger one, the buzz was finally all gone.

I don't know exact reason but you should use regular, big toggle for a power switch although small one has enough power load.

Now I have fully functional tube microphone. Thank you all Group DIY builders who are sharing their knowledge and experience.

 

[C12VR]

How do you wire up the pattern switch? I assumed com to the center lug of the switch in the BOM and omni and cardioid to the other two lugs respectively.

 

[C12VR]

bump

 

[C12VR]

For such a fantastic project there isn't much documentation on the assembly of the psu

 

[innercityman]

How do you wire up the pattern switch? I assumed com to the center lug of the switch in the BOM and omni and cardioid to the other two lugs respectively.

You can wire it up as you want, com in center lug obviously. Up to you to choose to have cardioid in left or right position.

 

[Silas]

Hi All,
I’m thinking of building the DEF47 in the UK - I wondered if anyone on here might know - are there any alterations I need to make to the PSU transformer to work with the UK voltage?
Many thanks
Silas

 

[C12VR]

You can wire it up as you want, com in center lug obviously. Up to you to choose to have cardioid in left or right position.

What confuses me is the diagram at the top of page 16 which has cardiod and omni wired together on one of the outside lugs and a connection to 0v on the other lug. Is this malarkey or should I wire it this way?

 

[oongbac]

Hi All,
I’m thinking of building the DEF47 in the UK - I wondered if anyone on here might know - are there any alterations I need to make to the PSU transformer to work with the UK voltage?
Many thanks
Silas

You can find the informations about it on page 15. And in the BOM, there are both transformers(115/230), so you can select one for you.

 

[oongbac]

What confuses me is the diagram at the top of page 16 which has cardiod and omni wired together on one of the outside lugs and a connection to 0v on the other lug. Is this malarkey or should I wire it this way?View attachment 96723

I wired com to center tap, crd to left and om to right. It works flawlessly. Of course you can swap left and right.