Neumann Vintage U87 Clone : Build Thread.

[GhostlyStudio]

Hmm. I have a JLI TSC-2 that I just ordered and am wondering how to make this work since the backplates aren’t isolated. Ideas? Ripped off by the JLI?

I went with JLI after watching @Wordsushi 's YouTube vid recommending them and I suspect that in the past they've maybe had different capsules and have changed supplier maybe? I can definitely say that their capsule isn't a Takstar for sure.

 

[joulupukki]

I went with JLI after watching @Wordsushi 's YouTube vid recommending them and I suspect that in the past they've maybe had different capsules and have changed supplier maybe? I can definitely say that their capsule isn't a Takstar for sure.

Yeah, the capsule looks different from the picture they show on their website. If I could figure out how to eke out some more sensitivity so I wouldn’t have to turn my preamp up so high, that’d make it better, for sure. I mostly use cardioid and so not having Fig8 isn’t a huge downer. I’m going to try changing the Zener from 24V to 33V first and see if sensitivity improves a little.

 

[deanrichard]

I̶'v̶e̶ j̶u̶s̶t̶ f̶i̶n̶i̶s̶h̶e̶d̶ m̶y̶ U̶8̶7̶ b̶u̶i̶l̶d̶ u̶s̶i̶n̶g̶ D̶a̶n̶n̶y̶'s̶ b̶l̶u̶e̶ p̶c̶b̶'s̶ a̶n̶d̶ B̶O̶M̶, a̶s̶ w̶e̶l̶l̶ a̶s̶ a̶n̶ A̶M̶I̶ T̶1̶3̶ t̶r̶a̶n̶s̶f̶o̶r̶m̶e̶r̶, a̶n̶d̶ f̶o̶l̶l̶o̶w̶e̶d̶ t̶h̶e̶ b̶u̶i̶l̶d̶ g̶u̶i̶d̶e̶ o̶n̶ h̶i̶s̶ w̶e̶b̶s̶i̶t̶e̶. C̶h̶u̶c̶k̶e̶d̶ i̶n̶ a̶ T̶S̶C̶-̶2̶ c̶a̶p̶s̶u̶l̶e̶ f̶r̶o̶m̶ J̶L̶I̶ t̶o̶ c̶h̶e̶c̶k̶ e̶v̶e̶r̶y̶t̶h̶i̶n̶g̶ w̶o̶r̶k̶s̶ f̶i̶n̶e̶ w̶h̶i̶l̶s̶t̶ I̶ w̶a̶i̶t̶ f̶o̶r̶ o̶n̶e̶ o̶f̶ A̶r̶i̶e̶n̶n̶e̶'s̶ K̶8̶7̶'s̶ t̶o̶ a̶r̶r̶i̶v̶e̶ a̶n̶d̶ e̶v̶e̶r̶y̶t̶h̶i̶n̶g̶ a̶p̶p̶e̶a̶r̶s̶ t̶o̶ w̶o̶r̶k̶ a̶s̶ e̶x̶p̶e̶c̶t̶e̶d̶, b̶u̶t̶ t̶h̶e̶ o̶u̶t̶p̶u̶t̶ s̶e̶e̶m̶s̶ q̶u̶i̶t̶e̶ l̶o̶w̶?̶ P̶l̶u̶g̶g̶e̶d̶ i̶n̶ m̶y̶ A̶K̶G̶ P̶4̶2̶0̶ i̶n̶t̶o̶ t̶h̶e̶ s̶a̶m̶e̶ a̶u̶d̶i̶o̶ i̶n̶t̶e̶r̶f̶a̶c̶e̶ a̶n̶d̶ t̶h̶e̶ d̶i̶f̶f̶e̶r̶e̶n̶c̶e̶ i̶n̶ v̶o̶l̶u̶m̶e̶ i̶s̶ n̶o̶t̶i̶c̶e̶a̶b̶l̶e̶. I̶s̶ t̶h̶e̶r̶e̶ a̶ g̶o̶o̶d̶ p̶l̶a̶c̶e̶ t̶o̶ s̶t̶a̶r̶t̶ i̶n̶ t̶e̶r̶m̶s̶ o̶f̶ d̶e̶b̶u̶g̶g̶i̶n̶g̶ w̶h̶e̶r̶e̶ I̶'v̶e̶ l̶i̶k̶e̶l̶y̶ g̶o̶n̶e̶ w̶r̶o̶n̶g̶?̶

Sorry, cancel that... I think I misunderstood that the original U87 circuit has less output compared to the U87ai (which the P420 is modelled off). I'm able to give more gain and speaking normally into the Mic comes out fine / clean.

Regarding your low output, I can't speak to the TSC-2 capsule, but I have installed two of the TSC-1's in MCA SP-1 mics, and they seem very high output to me. They are maybe 2-3 db hotter than the JLI-103 and the Baifeili L81 that I put in my other two MCA SP-1's. Now I don't have a U87 for reference, and I wasn't trying to build a U87, just improve the sound of the old MCA SP1's I had laying around. For that purpose, I am very pleased with the TSC-1 capsules. I don't have any measurements to back up my opinion, but they sound good to me.

 

[joulupukki]

I wonder if it could be that it doesn’t have isolated backplates and I connected the backplate wire to the PCB using the RBK terminal and maybe it needs to be on the FBK instead?

Would there be a way with Dany’s PCB to make it so all three polar patterns (Omni/Cardioid/Fig8) would work on the TSC-2 since it has non-isolated backplates? Seems like I remember seeing a discussion on the Fuchs 87A board where you could make all polar patterns work regardless of whether the capsule had isolated backplates or not.

 

[OneRoomStudio]

If you use a DC step-up circuit, "AI" style, you can generated all patterns without isolated backplates (U87AI didn't use isolated backplates).


If you want to stick to phantom power, it's a little trickier. You could try putting half-voltage (~24V) on the backplate and 48V on the front diaphragm, then switch the rear diaphragm between 0V (giving you figure-8), 24V (giving you cardioid), and 48V (giving you omni). Since you'd only have a 24V differential between the backplate and the diaphragms, you'd loose about 6dB of signal compared to a "standard" U87.

 

[joulupukki]

If you use a DC step-up circuit, "AI" style, you can generated all patterns without isolated backplates (U87AI didn't use isolated backplates).
View attachment 138660

If you want to stick to phantom power, it's a little trickier. You could try putting half-voltage (~24V) on the backplate and 48V on the front diaphragm, then switch the rear diaphragm between 0V (giving you figure-8), 24V (giving you cardioid), and 48V (giving you omni). Since you'd only have a 24V differential between the backplate and the diaphragms, you'd loose about 6dB of signal compared to a "standard" U87.

Gotcha. I care more about a stronger signal in Cardioid. I can live without Fig8 on this mic.

 

[OneRoomStudio]

Gotcha. I care more about a stronger signal in Cardioid. I can live without Fig8 on this mic.

If that's the case, it's easy to get only cardioid and omni (figure-8 is the tricky one). Keep the front diaphragm at ground potential (feeding directly into the FET), put your polarizing voltage (P48) on the backplate, and then use a switch to either disconnect the rear diaphragm (putting you in true cardioid), or connect the read diaphragm to the font diaphragm (putting both at ground potential, giving you omni).

 

[joulupukki]

If that's the case, it's easy to get only cardioid and omni (figure-8 is the tricky one). Keep the front diaphragm at ground potential (feeding directly into the FET), put your polarizing voltage (P48) on the backplate, and then use a switch to either disconnect the rear diaphragm (putting you in true cardioid), or connect the read diaphragm to the font diaphragm (putting both at ground potential, giving you omni).

Yep. That’s how it’s working currently. It just suffers from lower output levels with the JLI TSC-2 compared with the Arienne Audio K87 v1 capsule. I ordered a 33V Zener and will swap out the 24V Zener just to see. Even just a few more dB would help it be a more usable mic so I wouldn’t have to turn the preamp up so high.

 

[jBam]

[EDIT: I've decided not to clean or use headers... i figure i'll assume the no clean flux does what it says for at least the foreseeable future ]

Hi gang - side topic, as I finally begin these (paired) builds... two quick questions for anyone who may be able to assist:

No-clean solder: I've paused the build prior to polystyrene caps. I'm using Kester 275 (Sn63Pb37) No CLean... Just wanting to get a solid thought on whether i should clean or not clean. i.e. "no need to clean"; or "cleaning is fine, but could actually cause issues if you're not thorough enough - don't bother because no clean is fine"; or "yeah, you should still clean "no clean"."

Reading extensively online it seems there's applications where No Clean can still cause issues (unless thoroughly cleaned); but those are "extreme" conditions or scenarios. I bought the stuff to avoid cleaning of course, because, even with gloves, I want minimum board handling with the intent of best performance

The other questions is about the various headers in the BOM... sorry if I'm not in far enough, but I can't seem to see where I would actually use these... are they "optional" for wiring purposes...?? I might be confused, but keep running through example builds and am not seeing them used. I'm happy to use them, happy to leave them out. Not sure if they're for "push together" assembly in a particular body? I have SYT-5.

Thanks in advance

 

[kantaro]

Hi all, would this Aluminum Electrolytic Capacitors - Axial Leaded 10uF 63V 20% be a suitable replacement for the now obsolete one in the original BOM

replacement
https://www.mouser.com/ProductDetail/CDE-Illinois-Capacitor/106TTA063M?qs=3tP%2BN51vMXf8RloM9VWWPQ==

original now obsolete
https://www.mouser.com/ProductDetail/?qs=EVG5pHsmE1wcsUbS6ZU0wg==

 

[doggy6812]

I believe that it will work.

 

[Potato Cakes]

Does anyone have a part number for the standoffs shown in the opening thread that attach the switch PCB to the bottom of plate under the head basket?

Thanks!

Paul

 

[Potato Cakes]

I found out that I the tapered PCB sets that I bought and built did not fit the SYT-5 bodies I had on hand and had installed Arienne's k87 capsules. So instead of building another set of boards that were the correct dimensions and selling these off, I went the harder route, which was to figure out how to fit these in a body that is too small for the boards.

I picked up a pair of new/open box MXL 2003a's for less that $100 each, so I went ahead and ordered another set of transformers and capsules. From the photos of the MXL, it looked like the tapered PCBs would fit directly but I did not realize how much narrower it was until it arrived. However, the alternations to make these boards work is not that bad.

First, the sides of the boards have to be cut to the outer edge of the original screw mounting hole position. Then new holes need to be drilled. On the board with the capsule and switch connections, one of the hole goes right against one of the traces for the rear capsule connection (circled in red). This particular one did not make continuity however the other one did, so I went ahead and cut the traces around this new screw hole just to be certain and used some wire to remake those connections. With the preamp PCB I had one of the drill positions very close to the positive primary connection. I elongated the hole slightly just so I could see the smallest amount of solder mask between the screw head and the solder pad. I did not have the correct size nylon washer or this would have not been a consideration.

What I would to have liked to have done differently was the switch PCB. The MXL comes with two switches that do a high pass filter and -10dB pad. I had it in my mind that I wanted to use the switch PCB I got from Danny, and for some reason during test fitting I did not notice that the switches stuck out too far and that I only need to make a new cut out for the polarity switch. Not until made all of the new cuts did I realize they were sticking out further than I would have liked. I should have just kept the original switch board and then put a right angled toggle directly on the PCB for pattern switching. I had done this very thing on another build but it didn't dawn on me until it was too late.

The other issue with using the three switch board is that the head basket is held in place with the same screws that hold the control PCB in place. One of the mounting holes is directly underneath the pattern switch, so only one of the screws can be used to attach the board in place. I do not have a good way of drilling and tapping a threaded hole that small, so I glued the other stand off to the board and then to the plate under the head basket. Once the body is fully assembled the switches don't move around.

Both calibrate to 11.5VDC per build guide on Danny's website, so it seems that everything should be good once the capsules arrive.

Also, the transformer had to be hot glued in place as there was no good place to zip tie it. Now I'm just waiting on some capsules.

I should have also thought to use CAD GXL3000's. I think the body dimensions are similar and it already has all three switched in it's design.

All in all this was a fun little afternoon project to fit a full U87 circuit in a body that is noticeably smaller than the SYT-5 style units.

Thanks!

Paul

 

[Potato Cakes]

Also of note, for the mXL2003a it seems the ribs are bent in a little to work with the factory PCB. These should be straightened to allow for as much room as possible for Danny's tapered PCBs.

Thanks!

Paul