Neumann Vintage U87 Clone : Build Thread.

[DUDE GUY]

Can you verify that you xlr pin out is good ,
number 1 on pcb=  is hot  pin 2 xlr
number 2 on pcb= is cold pin 3 xlr
number 3 on pcb = gnd

verify on the silk screen if this is correct, it is labeled there ,

Dany,

Everything looks good, 1=pin 2, 2=pin 3, 3=ground

Correct me if I'm wrong, but if my voltages are good without the T13 and then my voltages go bad with it installed, doesn't that imply that there's an issue with my T13?

Thanks,

-DUDE GUY

 

[poctop]

where do you connect the traffo,  wich pad on the PCB you connect it  ,  could you measure the DC resistance of the coil and compare with a collegue here ,  if someone has a T13 available for measuring that would be extra so we could compare them , for T13 user

what is the configuration of the color code for it ? i just dont have on at the moment,

thanks for you precious input.,

Dan,

 

[Matador]

According to the spec sheet, the T13 primary is the two yellow wires, and the secondary is black.

With the transformer removed, you should show continuity between the two yellow wires.  You should also have continuity between the two blacks.  However there should not be continuity between any yellow and any black (with the transformer removed).  It almost sounds like there is a primary to secondary short, and since the primary is ground referenced, that would cause a short on the secondary side through the 2K2 resistors (and collapse the phantom voltage as well).

 

[DUDE GUY]

According to the spec sheet, the T13 primary is the two yellow wires, and the secondary is black.

With the transformer removed, you should show continuity between the two yellow wires.  You should also have continuity between the two blacks.  However there should not be continuity between any yellow and any black (with the transformer removed).  It almost sounds like there is a primary to secondary short, and since the primary is ground referenced, that would cause a short on the secondary side through the 2K2 resistors (and collapse the phantom voltage as well).

Hit the nail on the head, Matador! I have a short between my primary and secondary. That'll ruin your day! I'm going to contact AMI for a replacement ASAP. At least now I'll have two AMI stickers, double bonus! Ha.

Thanks for your help everyone, specifically matador, poctop, magnetosound, and wave. This is really an efficient and productive forum. I'll post my progress once I get a new T13.

-DUDE GUY

 

[wave]

Dudeguy,
For reference when you get your new AMI T-13





Dave

 

[DUDE GUY]

Awesome! Well done, thanks Dave.

 

[poctop]

Thanks For the Pointer Dave ,
Dan.,

 

[poctop]

I finally had a chance to put my RK-87 in the U1621 and compare it to my real Vintage Neumann , i have to say that i was lucky enough to be able to use the original traffo that a bought on ebay a while ago and the final results are that the RK-87 is pretty close to the original K-87 subtile differene in the top end wich the RK-87 has a bit higher top end and the transient were a bit sharper,  in the low end it would react pretty much the same, i did like the openess of the RK-87 as well,  Overall i would say that for the money the RK-87 is a very good investement , I had also the chance to compare the Modern flavor with film and electro instead of tantalum and polystyrene and i have to say that it did behave better with the tantalum and polystyrene flavor ,it was much closer to the real thing than the other combination ,  i really hope for those using the T13 with their build will be able to achieve comparable results with pairing the RK-87 to this project. 

Sincerly ,  ;D
Dan,

 

[berkleystudios]

i have been waiting for weeks for my CM2480 ??? how long does it take cinemag to make these things? im surprised i haven't heard anything yet. normally i would pay any mind but im trying to finish my testing of the RK87 for Matt and post results for everyone.

 

[sr1200]

NEVER send email to cinemag. Call them, you'll have it in less than a week.

 

[poctop]

I usually call and asked for invoice straight out  ;D that works great too.
D

 

[rmaier]

Yes. terrible email service, awesome phone service.

 

[Matador]

I finally had a chance to put my RK-87 in the U1621 and compare it to my real Vintage Neumann....

I wonder how much of the difference is due to the 3 micron Mylar (RK-87) vs. 6 micron (I believe the original)?

Here's a quick experiment:  increase the value of C6 (220pF) up to the 270pF to 330pF range and try the RK-87 again.  It will shave a few db off the high end in the 7k-10k range and not effect the gain too much.

 

[berkleystudios]

i already paid my invoice. is it possible they forgot? ill give them a call tomorrow.

 

[mparts]

I wonder how much of the difference is due to the 3 micron Mylar (RK-87) vs. 6 micron (I believe the original)?

The thinner film affects the high-frequency response, as you suggest, but it will have faster transient response, too, which is not something (IMO) Dan's vocal test would have revealed.

Historical note - Large-diaphragm capsules with thin film diaphragms (thinner than 6 micron) were pioneered by the late Stephen Paul. His eponymous firm lives on, and still provides capsule rebuilding and tuning with ultra-thin films, down to 0.9 micron (!).

 

[tskguy]

The thinner films also stretch out over time, Thats what I was told by some pretty well known capsule experts. I honestly havent been able to A B the difference  so I have no opinion on what sounds better. I think the Lawson microphone capsules use 3 micron skins as well. 

Eric

 

[wave]

[size=14pt]EXTREMELY HUGE NEWS!!!![/size]

I went to Guitar Center to get a shockmount for my mic. Whenever I have to buy anything from GC I buy from the GC Pro sales person at my local store as he can give me much better discounts than the regular staff.

So I called him up to see if they had a mount I could use and they did. I asked if he wanted me to bring the mic in to have a listen. He did.
I showed him the mic and I could tell, since it's still the bare brass and no logo yet, that he was a little unimpressed.
He showed it to a couple other sales people there and they decided that not only did they want to listen but they wanted to A/B my mic with a brand new Neumann U87 AI.
So we all go into the studio room where they have their computer recording gear set up and they plugged in the Neumann to a Focusrite Saffire.
We did some checks and some singing into the mic. Sounds like a U87 because it is.
Then we plugged in my mic.
Their faces showed astonishment. All 3 GC guys liked my mic way better. They commented on how warm and silky it sounded. "It sounds like a tube mic" was the phrase associated with my mic.
Now they want me to do a limited production of them and sell them in the store. I said I had to think about that.
They all want me to build them one!
I am sold on the RK-87. I think the capsule is intrinsic to the sound I'm getting. That and the combo of the styrenes and T-13 has yielded one very sweet mic and now I have the experience of putting it up side by side with a real U-87.

Great project Dany. You have given us the ability to make a great sounding unique microphone!

Also, I explained to them how I could use different components (capsule, trafo, caps..etc) to shape the sound of the mic differently and they all agreed that I should change nothing.



Dave

 

[saxmonster]

So did you get the shockmounth that is the important part here right?  HAHAHAHA Excellent news!!!!!!!!!!! 

 

[wave]

HAHA! I did get the shock mount. I also got some acoustic guitar strings so I can do some tests with my guitar (which was the other reason for going)

Dave

 

[saxmonster]

How does the pattern selection work on the PCB.  If I short pins 1 and 2 I get what? 2 and 3?  then is it 1 and 3?  I will just have to open the mic and do it by hand with the shuter/jumper clip thingy.

-Scott

Indeed,
No Jumper = Cardiod
Jumper (pin1-pin-2) = figure 8
Jumper (pin 2- pin-3)  = Omni,

Cheers,
Dan,

So without the jumper its Hyper Cardioid?  Not just cardioid right?

Also does anyone know what size screw are used for the transformer housing area.  There are 6 of them down there and one keeps coming loose and I think it might be the screw that is stripped not the hole.