OPEN SOURCE DIY Mic Project - ORS 87 - Stripped Down u87

[micolas]

OK, how do I wire the cartridge to accomplish this? Do i only connect the front side of the diaphragm and a ground? or is the rear lead grounded?

I haven't landed the contacts for the cartridge yes because I wasn't sure. I've got a ground lead connected using one of the mounting screws for the cartridge (seemed like a good path not requiring removing one of the cartridge assembly screws) but not fully sure how to proceed.

Thanks

eso

I proceed like this:
In the completed microphone, adjusted BIAS, etc., in perfect working order,
I mount the capsule, the wire from one diaphragm to the jFET input, the backplate to the circuit and the wire from the other diaphragm I leave it free.
I test the mic on vocals, guitar, other instruments, etc.
I disconnect the wire from the tested diaphragm and connect the other diaphragm. I test under the same conditions, on the same sources.
The side I like best will become Front.
I mark it with F. The other will be rear R.
Front remains active.
I connect the rear diaphragm wire to GND.

 

[eso]

... Front remains active.
I connect the rear diaphragm wire to GND.

So no additional ground to the cartridge body?

eso

 

[micolas]

So no additional ground to the cartridge body?

eso

There are 2 capsules back to back. Both backplates are common, galvanically connected by assembly, they are not electrically isolated.
As capsule K870, K67.
It has only 3 wires:
Front Diaphragm
Rear Diaphragm
Backplate - common
To GND you only connect the rear diaphragm.
*
The black wire is connected to both backplates.
*
https://groupdiy.com/threads/open-source-diy-mic-project-ors-87-stripped-down-u87.86814/post-1156263

 

[eso]

There are 2 capsules back to back. Both backplates are common, galvanically connected by assembly, they are not electrically isolated.
As capsule K870, K67.
It has only 3 wires:
Front Diaphragm
Rear Diaphragm
Backplate - common
To GND you only connect the rear diaphragm.
*
The black wire is connected to both backplates.
*
https://groupdiy.com/threads/open-source-diy-mic-project-ors-87-stripped-down-u87.86814/post-1156263

I received these cartridges with only two leads attached, front and back. There was also a bag supplied that had ground leads and mounting screws.

While I typically see grounds attached to these at one to the face screws around the perimeter, since the whole body looks like a chunk of brass I've connected the ground using one of the mounting screws. It's grounding to the entire body this way, isn't it? It just seems like a cleaner way to route the ground this way too.

You can sort of see the ground connection in this photo.

 

[Khron]

PS: Anyone interested in a 53.5x38mm (~2.1"x1.5"), single-layer, multi-donor-body-compatible, etch-at-home ORS87, with pad & high-pass?

View attachment 131370

Although truth be told, it's not all that much of a "stripped-down U87" anymore...

 

[micolas]

I received these cartridges with only two leads attached, front and back. There was also a bag supplied that had ground leads and mounting screws.

While I typically see grounds attached to these at one to the face screws around the perimeter, since the whole body looks like a chunk of brass I've connected the ground using one of the mounting screws. It's grounding to the entire body this way, isn't it? It just seems like a cleaner way to route the ground this way too.

You can sort of see the ground connection in this photo.

The 'chunk of brass' is actually the two electrically connected backplates
I have explained in detail previously.
The capsule normally has no GND.

So,the white wire in front is the Front Diaphragm and connects to the gate of the jFET
The blue wire is the backplate and is connected to the polarization voltage through the 1Mohm resistor. (and to the 33nF capacitor)

The white wire from the rear diaphragm connects to GND. Some leave it free but it can cause problems.
Follow the previous directions, choose the part that sounds best as Front.

 

[micolas]

View attachment 131481

Wow!
@Khron +1

 

[micolas]

While I typically see grounds attached to these at one to the face screws around the perimeter, since the whole body looks like a chunk of brass I've connected the ground using one of the mounting screws. It's grounding to the entire body this way, isn't it? It just seems like a cleaner way to route the ground this way too.

@eso
this is how a K87 capsule is built (here in the picture is the Arienne capsule):

I repeat, constructively this type of capsule does not have GND.

 

[Khron]

the whole body looks like a chunk of brass I've connected the ground using one of the mounting screws.

I really don't think the blue capsule mount is conductive, so you've only "connected the ground" if the end of the wire connected with that mounting screw to the backplate(s), ended up getting soldered to a pad on the PCB that's connected to ground.

 

[micolas]

I really don't think the blue capsule mount is conductive, so you've only "connected the ground" if the end of the wire connected with that mounting screw to the backplate(s), ended up getting soldered to a pad on the PCB that's connected to ground.

If the screw with the blue wire is long enough and also served to fix the capsule in the saddle, then it has contact with the backplate. If you connect it to GND, the ORS87 circuit scheme is not respected, it will not work.

And then @Khron will have to explain to eso one more time what's wrong

 

[AdamFrisen]

View attachment 131481

Any way to buy these somehow?

 

[micolas]

Any way to buy these somehow?

If @Khron doesn't decide sooner to produce them for sale, next week they will be for sale on Ali...ready populated with components. Free shipping.
Summer Offer!

 

[Khron]

Any way to buy these somehow?

Well......

https://www.pcbway.com/project/shareproject/ORS87_Plus_Open_source_U87_mic_project_2922baaf.html

That being said, BOMs for Mouser and Digikey are still in progress (close to being done), but i'll only get to scrape together a build guide in a few weeks, after i get some blank boards made

 

[micolas]

Well......

https://www.pcbway.com/project/shareproject/ORS87_Plus_Open_source_U87_mic_project_2922baaf.html

That being said, BOMs for Mouser and Digikey are still in progress (close to being done), but i'll only get to scrape together a build guide in a few weeks, after i get some blank boards made

So the wannabes order PCBs directly on PCBWay and the project author's work will be rewarded with a sales commission?

 

[Khron]

So the wannabes order PCBs directly on PCBWay and the project author's work will be rewarded with a sales commission?

Apparently so Seems to be the standard way PCBway operates, with these "shared projects"... Not sure there's any way to deactivate that, unless it's linked to the type of license the project is listed under..?

Edit: Nope, it's just their way.

https://www.pcbway.com/blog/help_ce...y_PCBWay_Website_Exploration_05_17c562d8.html

Note: If others place an order through your shared project, PCBWay will donate 10% of the order amount (PCB/ assembly cost /3D Printing /CNC cost) to you for your contribution to the Open-Source Community. The commission will be put into your PCBWay account, and you can choose to withdraw it or just leave it in your account balance. Also, you can get beans through sharing creative projects. Beans can be used to redeem products or coupons from our gift store, which we will introduce more in our next video, just stay tuned!

 

[micolas]

@Khron
Something tells me this is just the beginning
Am I right to believe that other extremely interesting projects will follow?

 

[Khron]

@Khron
Something tells me this is just the beginning
Am I right to believe that other extremely interesting projects will follow?

Well, i didn't put that feeler thread up just for fun But those won't be on PCBway...

 

[micolas]

@Khron
Connecting BP to the gate of the jFET does not change the polarity of the signal or the overall operation of the circuit.
Is it just elegant avoidance of any possible licensing controversy?

 

[Jedias]

Hey guys, I made this version of the circuit in stripboard. I'll share here so that anyone can use it.

 

[Khron]

@Khron
Connecting BP to the gate of the jFET does not change the polarity of the signal or the overall operation of the circuit.
Is it just elegant avoidance of any possible licensing controversy?

If it is, it's not intentional Nah, it's more like a "leftover" from other projects, that's all.