Neumann Vintage U87 Clone : Build Thread.

[FarisElek]

Found a link to Chunger's build and I think my transformer is wired opposite to the colors on the datasheet like this. If the ohm is 430r-ish between the two black wires, that means they're the secondary? I figured the bigger number meant primary.

 

[FarisElek]

YO! I finally got sound passing. I have to crank my pre ALL THE WAY. Getting 23v at Zener diode.  Help.

 

[FarisElek]

My voltages:
R18 - 45.58VDC (shematic: 46.6VDC)
R19 - 45.22VDC (shematic: 46.6VDC)
Zener -  22.82VDC (shematic: 23.6VDC)
R12 - 4.144vdc
R14 - 19.53vdc
C10 - 42VDC on right side, 38 VDC on left (shematic: 20.62VDC)
C5 - 42VDC on right side 0 VDC on left (shematic: 40VDC)
FC - 5.93v on FD, 38.24vdc on FBK (shematic: 40VDC)

 

[FarisElek]

Welp, I got it to work. Not sure what I did different but it's working. It does seem to be a bit quiet and the proximity effect is pretty crazy. I feel like you kind of have to sing up on the mic for it to sound good and for the gain settings to not be cranked too hot. But I've never used a Neumann u87 so maybe this is normal? I ordered another PCB so now that I know what I'm doing and I don't have to unsolder a million times I can compare and see if maybe there is something wrong with this build.


Ryan

 

[Ricardus]

Do you have any other condenser mics? In other words is it in the gain ballpark compared to other mics? Because it's a clone of the original U87 it actually should have LESS gain than most modern condensers, but is it close to any other LDCs you have?

Proximity effect isn't really about how well it picks up from 3 ft away as compared to 6 inches away. Proximity effect is about the mic putting out more low end the closer you get the diaphragm. This is a phenomenon common in all mics that aren't true Omnis.

According to the Neumann web site:

"The proximity effect is a phenomenon that leads to an increase in low frequency response as you move the mic closer to the source. The closer you get, the bigger the bass boost. This can create problems, but at the same time it opens up ways to shape the sound."

So you say you did nothing and it started to work?

 

[FarisElek]

It's not really within ballpark. It's probably about 10-15db lower than any of my other mics. I rarely go as high as I am right not on my preamp. Although, it's not THAT crazy high, just more than usual. The 10db cut makes it 10db even lower, so it's not that. What I meant about my statement is that I'd resoldered and desoldered several components several times and suddenly this time worked. I haven't yet tried to properly bias the fet. I only did a rough bias  hitting 11.5 and tested. I'm going to go back and scope it out. I think it wouldn't be a bad idea to unsolder the polystyrene and give the PCB a scrub as I'm sure I got flux everywhere.

However, if there is anything else I should look out for besides what I mentioned above to deal with the lower than usual output, I'd love to get your expert opinion. 

Kind Regards,
Ryan

 

[FarisElek]

Do you have any other condenser mics? In other words is it in the gain ballpark compared to other mics? Because it's a clone of the original U87 it actually should have LESS gain than most modern condensers, but is it close to any other LDCs you have?

Proximity effect isn't really about how well it picks up from 3 ft away as compared to 6 inches away. Proximity effect is about the mic putting out more low end the closer you get the diaphragm. This is a phenomenon common in all mics that aren't true Omnis.

According to the Neumann web site:

"The proximity effect is a phenomenon that leads to an increase in low frequency response as you move the mic closer to the source. The closer you get, the bigger the bass boost. This can create problems, but at the same time it opens up ways to shape the sound."

So you say you did nothing and it started to work?

Also, Omni isn't working, but figure 8 is. I'm assuming this has something to do with messy flux.

 

[FarisElek]

Ok new problem. Went back and did the best I could to clean the PCB and installed everything with gloves. Now the Low-cut doesn't work and the crystal clear and clean sound coming through cuts in and out. Anyone have any idea and what's happening now? I feel like I'm going to be an expert in this thing in no time 

Ryan

 

[FarisElek]

Welp, went back in and resoldered some of the things i disconnected during cleaning and now I've got everything working perfectly besides polar patterns. Cardioid only for now. I think I can assume that it's probably cold solder joints somewhere. I feel overall humbled by this experience and it sounds honestly amazing.

Thank y'all.

 

[FarisElek]

Ok last question:

Figure 8 is VERY much brighter on front than on back. Figure 8 is also louder on front than in cardioid mode. Is this normal becasue of the sound picking up on both sides?

Ryan

 

[FarisElek]

Reheated the solder (again) on all the points on the PCB's and now I have the same volume on all patterns. Very clear and loud now too. I don't have to push the gain at all. Really happy about that. Downside is that the capsule rear is still very weak on figure 8 and omni. I'm going to look at the schematic and see everything in the rear capsule signal path and try to reheat it, or maybe even pull the solder out and resolder it.

 

[FarisElek]

Spent the last week over-reading everything and studying the schematic. About to start all over as I'm fairly certain I fried some components or. At this point ONLY figure 8 works perfectly  .

 

[Ricardus]

Oh my.

What is starting over? Replacing every component on the boards?

 

[FarisElek]

I redid the entire 2nd PCB with the polystyrenes because every time I reheated solder on that side something different happened to the mic. I un-soldered the entire board an cleaned it and found a couple components that weren't working. right probably due to excessive heat from my clumpy as heck solder not melting and the excessive amount of time I was holding the iron to it. Picked up some new solder, some other tools, worked with gloves, and got a  couple replacement caps and resistors and now it's working 100%.


Note to any build mic newbs: Read this forum deeply before starting, wear powdlerless nitrile gloves, keep 91% isopropyl alcohol nearby to clean off flux (but not after installing the polystyrenes because it will mess with them and I think that may have been one of my problems too), IMO use small 0.5mm solder so it doesn't get clumpy and melts quickly without having to apply heat for too long on the pcb. Also, consider having some sort of vise nearby, the extra hand is invaluable. Oh, and make wires from switch PCB not too long. Too long and too little are both the worst for all this mic's wiring, especially if you have pretty rigid wires like I do. All of my answers were answered before I asked them but I was too lazy to read this entire forum and it made me learn the hard way, so do a lot of thoughtful consideration before starting. It's not like building a pre or pedal. It's pretty damn delicate.


Ryan

 

[Ricardus]

I actually use the 99.5% alcohol, but I had to special order it.

So does it work now?

 

[FarisElek]

Yeah, it's works good now! I feel like I can build one with my eyes closed after reading this forum for hours and studying the schematic. Going to build another now. Hopefully I'll never have to post again haha.

Ryan

 

[Ricardus]

Post pics!

 

[FarisElek]

I should have time to post pics on Monday or Tuesday!

 

[FarisElek]

Here is one half

 

[FarisElek]

Here is the other. As you can see I had to trim down the switch PCB so it would fit in this tiny BM600 body.

It's not perfect looking but it doesn't even pop when I use the switches. I learned so so so much. Thank you for creating the PCB Dan, it's been a blast.