Neumann Vintage U87 Clone : Build Thread.

I have built 5 of these successfully, however now I have one that is noisy only on the Figure 8 pattern. Sounds like a rushing wind sound when set to Figure 8. It does pass audio, just has constant noise. Ive gone through and thoroughly cleaned up all of the high impedance connections and nothing changed.

I was then thinking it must be on the rear board. I had the parts on hand to build a new rear board and drop it in, but it didn't resolve the issue.

Has anyone has encountered this before?

Could it actually be the switch I am using? Using the switches from the SYT-5 kit.

Lots of info in this thread, hopefully someone can help me out. I just finished my build and followed Andrews instructions.

The only part I used thats different is the FET. I used an NTE312 (Dany suggested it earlier to someone else)  instead of the other one thats been discontinued.

My mic doesn't output anything but hiss when it is cranked all the way up.

Also, when measuring the drain, do i want my multimeter set to AC or DC?

When set to AC, I can set it to 11.5, but DC doesn't let me get that high of a value, not even close.

Any help is appreciated.

tsd80 said:

Lots of info in this thread, hopefully someone can help me out. I just finished my build and followed Andrews instructions.

The only part I used thats different is the FET. I used an NTE312 (Dany suggested it earlier to someone else)  instead of the other one thats been discontinued.

My mic doesn't output anything but hiss when it is cranked all the way up.

When set to AC, I can set it to 11.5, but DC doesn't let me get that high of a value, not even close.

Any help is appreciated.

Also, when measuring the drain, do i want my multimeter set to AC or DC?

Click to expand...

What voltage at drain do you get with meter set in dc? Also what is source voltage?

I have some of these NTE 312's as well but put one in a mic and wasn't right so swapped it out for another FET that I got form Fred.

PG_Sax said:

What voltage at drain do you get with meter set in dc? Also what is source voltage?

I have some of these NTE 312's as well but put one in a mic and wasn't right so swapped it out for another FET that I got form Fred.

Click to expand...

5.7v in DC mode, 11.5v in AC

source volt is 45.5v

tsd80 said:

5.7v in DC mode, 11.5v in AC

source volt is 45.5v

Click to expand...

Ok something is definitely not right if source leg of FET is 45.5v? Are you definitely measuring from source leg of JFET?

If possible post some pictures of boards?

PG_Sax said:

Ok something is definitely not right if source leg of FET is 45.5v? Are you definitely measuring from source leg of JFET?

If possible post some pictures of boards?

Click to expand...

PG_Sax said:

Ok something is definitely not right if source leg of FET is 45.5v? Are you definitely measuring from source leg of JFET?

If possible post some pictures of boards?

Click to expand...

oh sorry i misunderstood, i thought you meant my phantom power voltage.

how can i measure the source of the FET? Multimeter on source pin and ground?

Also the pinout on this FET is G S D and the S i have going to the ground pin instead of the board per the instructions i followed. I wonder if the other FET has a different pin out?

Indeed it is a different pinout, I'm going to try to move some things around.

ugh, well I've tried what i thought was connecting  the gate lead to ground pin, the drain lead to drain side of pcb and the source lead to the opposite. No matter what i do, i either get a  loud hum, or nothing at all.

Im over it for the night, try again tomorrow. Am i reading the leads wrong? whats the proper way to orient the FET to identify the leads?

thanks

Is this the jfet you are using?

Can you post a picture of Board 1?

Also the jfet maybe dead now if you hooked it up wrong, so best to try a fresh one. Looks like you need to put jfet in the other way round (flat side away from pin) then your drain will be in right place but the gate is not in the middle and that needs to connect to pin, middle pin needs to connect to board as its source.

PG_Sax said:

Is this the jfet you are using?

Can you post a picture of Board 1?

Also the jfet maybe dead now if you hooked it up wrong, so best to try a fresh one. Looks like you need to put jfet in the other way round (flat side away from ground pin) then your drain will be in right place but the gate is not in the middle and that needs to connect to ground pin, middle pin needs to connect to board as its source.

Click to expand...

Yes that is the fet  I have. I've tried 2 different ones and I have one more that is unused. 

I'm fairly certain I connected it the way you describe first and it just hummed loudly.

I ordered some of the fairchild jfets but it will be a while til they get here since they are coming from the UK.

Ok it will hum loudly if you don't have the body of the mic on when you test it. You will get a lot of ground noise

It may not be the fet at all, I would check the orientation of the capacitors that have polarity and also go over the board and check continuity of wiring with your meter.

Did you check the voltages at the various other points on the board? There is a list somewhere on this thread I think.

I would buy some jfets from fsalter. I bought some from him and they have been great.

PG_Sax said:

Ok it will hum loudly if you don't have the body of the mic on when you test it. You will get a lot of ground noise

It may not be the fet at all, I would check the orientation of the capacitors that have polarity and also go over the board and check continuity of wiring with your meter.

Did you check the voltages at the various other points on the board? There is a list somewhere on this thread I think.

I would buy some jfets from fsalter. I bought some from him and they have been great.

Click to expand...

I did double check the polarity of the caps, those look good.  + symbol on the positive lead. I took my time so I shouldnt have mucked things up too badly but the different pinout of the fet definitely got me.

I did have the fet installed how we discussed when I got the hum but yes the body was not on the mic so maybe I'll try my last fet in the proper orientation and put the body on and see what happens.

Thanks

Well I'll be a monkeys uncle. It works.

Things I noticed from a quick listen. Filter and pad work. Omni and cardioid sound good.

Figure 8 is a slight mismatch in levels from one side to the other.  Does this have to do with the 2.2k resistors not being matched close enough? Or should I just make sure my capsule wiring is making a good connection.

It sounds clean. No hiss, hum, or distortion of any kind.

Now that I'm thinking about it maybe I should check the switch wiring... tomorrow is another day  :

Hi guys,

I started my build yesterday. I am pretty new to this so having some trouble figuring out what components go where.
I can't find L1 and L2 on the schematic, and also not in the build logs, also I don't seem to have parts that look like the ones I see in the photos here. Are they resistors? Diodes?

Thanks!

Chris

tsd80 said:

Well I'll be a monkeys uncle. It works.

Things I noticed from a quick listen. Filter and pad work. Omni and cardioid sound good.

Figure 8 is a slight mismatch in levels from one side to the other.  Does this have to do with the 2.2k resistors not being matched close enough? Or should I just make sure my capsule wiring is making a good connection.

It sounds clean. No hiss, hum, or distortion of any kind.

Now that I'm thinking about it maybe I should check the switch wiring... tomorrow is another day  :

Click to expand...

Great! Glad you got it working. Figure of 8 may sound different as the rear is inverted so if you are listening on headphones you will get a slight difference in sound from one side to the other.

Out of interest what is omni like? Are the levels evenly matched from the front and back?

Duizels said:

Hi guys,

I started my build yesterday. I am pretty new to this so having some trouble figuring out what components go where.
I can't find L1 and L2 on the schematic, and also not in the build logs, also I don't seem to have parts that look like the ones I see in the photos here. Are they resistors? Diodes?

Thanks!

Chris

Click to expand...

L1 and L2 are on board 1 Schematic next to xlr input. If I remember rightly they are chokes. There is a spreadsheet of all the different components on page 1 of this thread I think.

PG_Sax said:

Great! Glad you got it working. Figure of 8 may sound different as the rear is inverted so if you are listening on headphones you will get a slight difference in sound from one side to the other.

Out of interest what is omni like? Are the levels evenly matched from the front and back?

Click to expand...

Omni is indiscernible from one another.

I was listening on headphones so that makes sense about 8.

Thanks for taking the time to help me out!

To anyone using the NTE312, THE LEADS ARE IN A DIFFERENT ORDER!

Cheers!

Hey guys,

Another question: The Jfet. The instructions say I need to connect the Drain leg to the ground pin.
When I google the jFet it seems the Drain leg is one of the outer pins, not the middle one. But when I look at several build photos, it looks as if the middle leg is connected to the ground teflon pin.

What should I do?

Thanks!

Chris

Which instructions are you looking at? If you look at page 1 you will see a picture of board 1 with an arrow showing you were you measure the drain calibration voltage from. The gate of the fet should connect to the pin, this could be the middle one depending on the fet. It depends on what JFET you are using as to which pin is which. The source and drain connect to board.

tsd80 said:

Omni is indiscernible from one another.

I was listening on headphones so that makes sense about 8.

Thanks for taking the time to help me out!

To anyone using the NTE312, THE LEADS ARE IN A DIFFERENT ORDER!

Cheers!

Click to expand...

No worries. Glad you got it working.