U87 (Revision A) in BM800 microphone donor body

[antocu]

Hi Ross, I got it from aliexpress, here's the link 26.64US $ 56% di SCONTO|HISINGWELL microfono di registrazione capacitivo interamente in metallo per Laptop Windows Cardioid Studio, musica vocale|Microphones| - AliExpress
There's a little issue with the central screw mountings as they are threaded only on one side, but in my case it wasn't a problem as the pcbs are kept together by the pins. If you need some photos just let me know

Bye
Gabriele

 

[c1184701]

Hi Ross, I got it from aliexpress, here's the link 26.64US $ 56% di SCONTO|HISINGWELL microfono di registrazione capacitivo interamente in metallo per Laptop Windows Cardioid Studio, musica vocale|Microphones| - AliExpress
There's a little issue with the central screw mountings as they are threaded only on one side, but in my case it wasn't a problem as the pcbs are kept together by the pins. If you need some photos just let me know

Bye
Gabriele

Thanks for the link Gabriele.

So the two-pin connectors at the top and bottom of the pcb will keep them held together, if only one of the pcbs can be screwed into the central mounting?

 

[antocu]

Exactly

 

[antocu]

Hello, I've recently done a recording for a friend and I'd like to share a little excerpt with you, here is the drive
The mics are in AB configuration with a cardiod pattern. Recorded into a zoomh6 with no eq or fx. Hope you enjoy

 

[MicMaven]

The mics are in AB configuration with a cardiod pattern. Recorded into a zoomh6 with no eq or fx. Hope you enjoy

Nice. Novice Question: How far were the microphones from the instrument? Thanks. James - K8JHR

 

[k brown]

The significant resonances of the thin, light BM-800 bodies really need to be addressed for the mic sound it's best. At the very least, a layer of self-adhesive craft foam sheet; even better is as much of this sort of material as can be packed inside. I also do the inner frame and bottom of the capsule mounting plate.
https://www.amazon.com/Fittings-Uni...671389952&sprefix=coax+sealant,aps,430&sr=8-3

 

[MicMaven]

Right. I wrapped a strip of foam packing material around the internal frame and circuit board of my last BM-800 build to dampen body vibration. It made a big difference. A little extra open cell (different type) foam minimized deleterious resonance in the head basket. Sounds good ... now.

Parenthetically, Coax Seal is useful, but rather expensive for what is, essentially, automotive sound dampening material. 5 feet of Coax Seal usually costs $13 - while 15 meters/30ft automotive sealer costs about the same. (I drive a hard bargain.) Ham radio operators weather seal outdoor PL-259 coax connectors. (Mentioned just in case you wondered ...) / James

 

[k brown]

This stuff is cheaper, but a little less dense:
https://www.amazon.com/Skywalker-Si...7&sr=1-1-f0029781-b79b-4b60-9cb0-eeda4dea34d6

 

[c1184701]

The significant resonances of the thin, light BM-800 bodies really need to be addressed for the mic sound it's best. At the very least, a layer of self-adhesive craft foam sheet; even better is as much of this sort of material as can be packed inside. I also do the inner frame and bottom of the capsule mounting plate.
https://www.amazon.com/Fittings-Uni...671389952&sprefix=coax+sealant,aps,430&sr=8-3

Right. I wrapped a strip of foam packing material around the internal frame and circuit board of my last BM-800 build to dampen body vibration. It made a big difference. A little extra open cell (different type) foam minimized deleterious resonance in the head basket. Sounds good ... now.

Parenthetically, Coax Seal is useful, but rather expensive for what is, essentially, automotive sound dampening material. 5 feet of Coax Seal usually costs $13 - while 15 meters/30ft automotive sealer costs about the same. (I drive a hard bargain.) Ham radio operators weather seal outdoor PL-259 coax connectors. (Mentioned just in case you wondered ...) / James

Useful information thanks guys. I have 4 BM-800 bodies that I am planning to build out soon, and I was concerned about the nasty pingy resonances they have around 1kHz. If you have any pics of the dampening you have done to your mics I'd love to see them

 

[antocu]

Nice. Novice Question: How far were the microphones from the instrument? Thanks. James - K8JHR

I would say 1.20 meters away from the guitar pointing to the 12 fret and the bridge..

The significant resonances of the thin, light BM-800 bodies really need to be addressed for the mic sound it's best. At the very least, a layer of self-adhesive craft foam sheet; even better is as much of this sort of material as can be packed inside. I also do the inner frame and bottom of the capsule mounting plate.
https://www.amazon.com/Fittings-Uni...671389952&sprefix=coax+sealant,aps,430&sr=8-3

You're right for the Bm800 body, but I didn't have this problem with the u87 style body I bought from Aliexpress which are more robust. I'm curious to see some pics of the dampening too as for some projects I'm going to use the Bm800 body and probably consider doing what you suggested.

 

[k brown]

Useful information thanks guys. I have 4 BM-800 bodies that I am planning to build out soon, and I was concerned about the nasty pingy resonances they have around 1kHz. If you have any pics of the dampening you have done to your mics I'd love to see them

Nuthin' too fancy -

Not a lot space in those BM bodies between the frame and shell; the craft foam just fits - the coax seal, I covered with painter's tape so it can 'shimmy' past the frame's bottom disc more easily. Last pic shows a couple of blobs of 3M Mastic Tape (much denser/more deadening than Coax Seal, but expensive and not as easily malleable) underneath the capsule plate.

Of course, everybody knows blue is the most sound-deadening color ; - )

 

[MicMaven]

... If you have any pics of the dampening you have done to your mics I'd love to see them ...

These photos depict how I have damped body tubes. Sometimes I past rubber like pads, and other times I wrap the internal frames with packing foam sheets cut to size. They pads do not touch the internal frames. The packing foam is paced so it touches both frame and outer tube at once. Just they way I do it. Happy Trails y'all. James /K8JHR

 

[Dimon]

Hi, of course, schematics are in your mailbox ;-) ...

Please send me all the schematics and specifications of components and photos for made a printed circuit board to create your wonderful version of the U87 microphone? if I may.

 

[mihi_fuchs]

Please send me all the schematics and specifications of components and photos for made a printed circuit board to create your wonderful version of the U87 microphone? if I may.

all the infos you‘re asking for are in this post already. just check page 1 ;-) …

 

[Dimon]

all the infos you‘re asking for are in this post already. just check page 1 ;-) …

Thank you, yes I saw a circuit scheme and an assembly manual, list parts there, but there is no how to make a PСB.

Of course, i can make the PCB in program, but I think it will not be perfect like yours. Or do I need to buy an assembly kit in the store? Which one?

 

[soundwave]

I started DIY three years ago right before all the lock down action started and as it provided quite some nice distraction I had quite some projects going. In the dropbox link below you can find my attempt on transferring a U87 based layout to the BM-800 donor body.
The donor body is particularly cheap and does the job well in my opinion.

In the link below you can find the BOM, a detailed building guide and some sound samples recording OH and some vocals with the mic. The sound samples are unprocessed unless otherwise stated (the vocals are also presented once with EQ). Both instruments were recorded by the U87-based clone in the BM800 body, with the Dachmann K87 capsule.

Here is the link:
https://www.dropbox.com/sh/70et2o4atzujc6x/AAAJNY-4vQnjCFEDbcRLeHWla?dl=0
View attachment 83620View attachment 83621View attachment 83623

I had to split the curcuit part into two because of the limited space. I used a Dachmann K87 with non-isolated backplates and a MAIKU K87 capsule with isolated backplates (both worked fine), a 3u audio GZT-87 transformer (ratio 9.5 : 1) and a 3D printed capsule holder. Most parts were obtained from mouser, the styroflex capacitors were purchased from reichelt.at and budgetronics (for details see the BOM in the dropbox folder).

Last but not least the project has been highly influenced and some solutions were simply copied from members of this forum (e.g. matador, khron, poctop, chunger, and others) - thanks for all of their posts, ideas and solutions that they have shared over the times. The FET biasing has been adopted from Mic&Mod as well as the additional connector for a sine wave to adjust the bias via a tone generator.

As there has been already a discussion about the BM-800 donor body maybe the sound samples prove helpful to some forum members.

As for the previous post I'll make some of the spare PCBs available on the black market for anyone interested

Thanks again for all the nice hours I spent browsing through this forum,
all the best
mike

Hi Michael,
do you have PCB's (latest version) of the project leftover for sale?
I would like to buy a set.
Thank you!
HERB

 

[mihi_fuchs]

Hi Michael,
do you have PCB's (latest version) of the project leftover for sale?
I would like to buy a set.
Thank you!
HERB

Hi Herb,
yes, still got few pieces laying around here. PM sent ;-)

 

[Dimon]

Hi Herb,
yes, still got few pieces laying around here. PM sent ;-)

I would like to buy a set too.

 

[c1184701]

I've just bought some parts from Mouser, and I discovered that the keystone turrets listed in the BOM have continuity from end to end. Wouldn't this negate the point of using them?

I ordered these ones, which are also listed on the BOM for the D-U87 project with the big thread.

Keystone 11218 at Mouser

 

[mihi_fuchs]

I've just bought some parts from Mouser, and I discovered that the keystone turrets listed in the BOM have continuity from end to end. Wouldn't this negate the point of using them?

I ordered these ones, which are also listed on the BOM for the D-U87 project with the big thread.

Keystone 11218 at Mouser

yes they do. but you isolate them via the teflon part. the hole in the pcb fits the teflon ring leading to no contact to the pcb. top and bottom part are conducting, but no contact to the pcb is there as the teflon parts isolates.