D-EF47 Tribute To Oliver Archut U47 Build Thread.

[AB_Music]

But please check with a DMM the ground connection.

I will check with DMM. Two questions…first…Do I connect the xlr pin 1 only to ground pin of the xlr connector or also to the ground terminal for xlr on the pcb?

second…if I don’t use the ground lift switch where do I connect the starground? To the 0V terminal or the pin 3 terminal?

 

[TillM]

The XLR 1 pin just to the xlr connector. No other connection. You can also leave your wiring from pcb to pin 2 and 3 at the XLR connector, but make sure you cut the pin 1 wire and just connect pin 1 to XLR ground pin.
The starground to the case.
Don't connect it to 0v terminal or pin 3 !!!

 

[AB_Music]

The XLR 1 pin just to the xlr connector. No other connection. You can also leave your wiring from pcb to pin 2 and 3 at the XLR connector, but make sure you cut the pin 1 wire and just connect pin 1 to XLR ground pin.
The starground to the case.
Don't connect it to 0v terminal or pin 3 !!!

Ok…so the pcb is only getting ground via the microphone? But why the connection from pcb to pin 3? Pin 3 in the microphone isn‘t connected to anything. Ground and shield are both on pin 7…or do I need to change that?

 

[TillM]

Please check with your DMM the ground connection from pin 3 microphone pcb to ground from from xlr 1.
It should be connected, if you do it right.
Just connect the mic with the tube cable to psu, but don’t start the psu.
Then check the ground from mic pcb pin 3 to xlr pin 1 and psu pcb 3 and 7. Don’t forget to use the jumper on the psu, as recommended.

 

[mrgrooves666]

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

Thanks! Even though I don't have issues, I want to implement this scheme. You never now when it could result handy. I guess its valid for all these neumann tube projects from Dany (67,49,47) as they all share similar grounding guidelines?

 

[TillM]

I Used it in all my builds. (M49, U47)
Get it from David (@TLRT), never had any issue with hum since I used it.

 

[AB_Music]

I Used it in all my builds. (M49, U47)
Get it from David (@TLRT), never had any issue with hum since I used it.

Tried it today…sadly makes no difference….hum is still there.

 

[Delta Sigma]

Tried it today…sadly makes no difference….hum is still there.

Are your audio connections still going to the PCB? Your audio pair should leave the 7 pin connector, then travel directly to the 3 pin XLR. The pair should be twisted tightly. If you can, route the audio pair away from the PCB.

 

[AB_Music]

Are your audio connections still going to the PCB? Your audio pair should leave the 7 pin connector, then travel directly to the 3 pin XLR. The pair should be twisted tightly. If you can, route the audio pair away from the PCB.

No, audio connections are not going to the pcb…they are going directly from 7 pin connector to the xlr. There seems to be some interference between the audio cables and the pcb. I’ve noticed some changes in the hum when I move the cables around in the psu case. I‘ve also tried using a shielded mic cable for the audio connections inside the psu. Not really a difference. But there is also a hum when the psu is turned of that doesn‘t change at all…no matter where I‘m moving the cables. I‘ve also made an interesting observation…when I turn off the psu, the hum gets more quite for the first 10 seconds and the slowly gets louder again.

 

[TillM]

Leave the jumper out at PSU pub and see what happens.

 

[AB_Music]

Leave the jumper out at PSU pub and see what happens.

You mean this jumper?
Had a quick look at the psu schematic...as far as I can read it, this jumper connects pin 3 of the 7 pin connector to ground...right? But pin 3 isn't connected to the mic anyway...my 7 pin connector in the mic leaves out pin 3 completely.
Pin 1 is A+
Pin 2 is A-
Pin 3 is (no wire connected)
Pin 4 is H+
Pin 5 is B+
Pin 6 is PTRN
Pin 7 is Ground

So, I've just tried it....removed the jumper....no difference.
I was expecting this...because it is't connected to the mic anyway.
Should I connect it to ground in mic? So pin 7 and pin 3 are both soldered to the ground pad in the mic?

I've just tried to make a ground connection to a few spots in the mic and see what's happening.
As I've connected P+ with the ground, the hum disappears completely. Just tried it with psu unpowered.
What does that say? Maybe the BV8 isn't working properly?

 

[TillM]

Yes I mean that jumper.
It seams to be, that you don’t have proper grounding in your microphone.
Connect pin 3 and 7.
How do you solder your mic cable?

 

[AB_Music]

Yes I mean that jumper.
It seams to be, that you don’t have proper grounding in your microphone.
Connect pin 3 and 7.
How do you solder your mic cable?

I've used the SC Octave Tube by Sommer Cables.
In the cable all wires are connected.
White = Pin 1
Red = Pin 2
Violet = Pin 3
Blue = Pin 4
Orange = Pin 5
Black = Pin 6
Shield and green = Pin 7

I've just tried connecting pin 7 and pin 3...no change...hum still there.
It's only gone when I connect ground to P+
Probably the problem is located there...because as far as I can read the schematic P- is connected to ground,
so P+ is the other side of the primary winding of the BV8 and should be connected to P- with some resistance between them (am I right?) but I can't measure a connection between P+ and P- and also can't measure a connection from P+ to ground.
Could that be the problem?....maybe a faulty BV8? Would the mic work like mine with a faulty BV8 or would it be totally quiet when the BV8 is defective?

 

[TillM]

When the hum is gone, then change p- and p+.
Which transformer do you use ?

 

[AB_Music]

When the hum is gone, then change p- and p+.
Which transformer do you use ?

I use the BV8 by Replica Microphones…bought at Mic&Mod

 

[TillM]

Oh no. Don’t tell me, that you pay so much for a cheap Chinese transformer.
Do you get a wiring schematic for the transformer? When you change the wires from p+ and p- do you also have hum?
Could you do a test, when you put your power transformer outside the psu?
Is your mic with a body, when you do the the tests for hum?

 

[AB_Music]

Oh no. Don’t tell me, that you pay so much for a cheap Chinese transformer.
Do you get a wiring schematic for the transformer? When you change the wires from p+ and p- do you also have hum?
Could you do a test, when you put your power transformer outside the psu?
Is your mic with a body, when you do the the tests for hum?

I haven't payed a lot for the transformer...bought it on sale.
No, I don't have wiring schematic for the transformer.
No difference in the hum after changing P+ and P-
I've done a test where I removed all transformers from the psu case and placed them as far away as possible from each other and the pcb...but hum was still there.
Mic is always in fully closed body when testing.
I just noticed, the hum is getting so much louder when I move the mic closer to the psu.
Almost sounds like a lightsaber when moving it above the psu.
Also cut the heater voltage while the mic is running, just to see if the hum will disappear while the tube is dying....but no, it is still there. And I've checked if removing the tube does anything when psu is turned off....nothing...hum is still there.
Same for the capsule...I've removed it from the circuit but hum is still there.
Can't find anything that looks faulty in the mic...even the grounds seem to be all good...I've checked them all with DMM.

 

[TLRT]

Check Neumann u67's psu as a good grounding reference. And I really recommend to protect your mic with zeners as this design has a big flaw, the pattern switch is powered from the B+ Line, so if the reed relay dies (it happens sometimes) your pattern switch will be a voltage doubler without the relay's internal resistance,so say goodbye to your capsule.

 

[mrgrooves666]

Check Neumann u67's psu as a good grounding reference. And I really recommend to protect your mic with zeners as this design has a big flaw, the pattern switch is powered from the B+ Line, so if the reed relay dies (it happens sometimes) your pattern switch will be a voltage doubler without the relay's internal resistance,so say goodbye to your capsule.

Could you share/describe how? Tnx!

 

[TLRT]

Could you share/describe how? Tnx!

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