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

[Khron]

sort like star GND?

Sort of, but like the complete opposite. But I'd rather let the designer himself explain.

 

[homero.leal]

Direct quote from LNPrimer.doc, by @ricardo The doc can be found on the MicBuilders forum.

"PCB layout is critical for low noise. The first rule is to be very clear what your earths are doing. I always define 3 earths; Clean, Dirty and Chassis. I won’t talk about evil Digital earths but see the above link on www.planetanalog.com Consider carefully what you are doing when you connect anything to an earth. If you connect supply decoupling capacitors to an earth line, you make it Dirty. In our simple circuit, Clean earth is used ONLY for input / output earths and feedback components. The 10k input resistor is taken to BP so this line must be treated like Clean earth. BP is joined to Clean earth via a single 47u right at the input sockets. Dirty earth carries our supply decoupling currents. The 3 earths are joined ONLY at one point, at the output in our simple circuit. Output current does not upset the Clean input and feedback paths; a common source of instability. Some of you will recognise this as similar to "Star Point" earthing in power amplifiers."

 

[Khron]

That may very well apply to line-level circuits powered from the mains grid, that interact with other equipment powered from the mains grid. Some appropriate context for that quote would have helped..?

Found @ricardo 's quote on this forum as well, but as expected from the wording, it refers to preamplifiers, NOT microphone impedance converters...

https://groupdiy.com/threads/ina134-and-drv134-supply-bypassing.56079/post-715735

Unless you have special mic cables that have a separate shield that connects ONLY to the mic chassis, and the circuit ground of the circuitry connects ONLY to XLR pin 1.

As far as I'm concerned, a phantom-powered microphone might as well be a "floating" system, since it ONLY connects to the preamp you plug it into (tube mics could have a ground-lift on the output XLR, but that's a different issue).

Really no idea how and what "ground loops" you can achieve inside a mic, but i haven't managed that yet, despite my "careless" and "unwise" use of ground planes

PS. I would also slightly object to there being multiple "earths" there - i've been taught "earth" is (strictly) mains earth; anything else is a (circuit) ground. If only to try to avoid confusion...

 

[Juan Vargas]

hi guys at the moment I got this layout that will fit into this cheapo Temu mic that please don't laugh at the tiny PCB , ok so I add an opening for the NTE10-3 transformer that can be secure with zip ties the PCB size will fit only on this type of body that looks like those real Telefunken microphones body style I want it to add this data here so the screws mounting for the frame top PCB fastening are about 28.5 mm wide the next screws down are about 28 mm and from this screw mounts down is about 52 mm PCB size is 37 mm x 90 mm I'm gonna continue checking the layout to make sure that there are no bugs I've been doing this for many years but there is always one "oh no I forgot to..." you know what I mean the only thing different that I add to the layout is another R* so to combine different value resistors after FET is adjusted and get the trim pot resistance value to R* final value good day guys

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[Korablev]

hi guys at the moment I got this layout that will fit into this cheapo Temu mic that please don't laugh at the tiny PCB , ok so I add an opening for the NTE10-3 transformer that can be secure with zip ties the PCB size will fit only on this type of body that looks like those real Telefunken microphones body style I want it to add this data here so the screws mounting for the frame top PCB fastening are about 28.5 mm wide the next screws down are about 28 mm and from this screw mounts down is about 52 mm PCB size is 37 mm x 90 mm I'm gonna continue checking the layout to make sure that there are no bugs I've been doing this for many years but there is always one "oh no I forgot to..." you know what I mean the only thing different that I add to the layout is another R* so to combine different value resistors after FET is adjusted and get the trim pot resistance value to R* final value good day guys

​

Dear Juan Vargas.
Are you planning to make the gerber file available for free use or sell it so that I can order a PCB of your version on Aliexpress?
The thing is that the bolt pattern of your board version is ideal for my case, which I recently purchased on Aliexpress.
https://aliexpress.ru/item/10050064...l.0.0.20204aa6XU8jLw&sku_id=12000037309239239
I would like to take this opportunity to say a big thank you to everyone who actively worked on this project. This is simply a wonderful opportunity to try to assemble a clone of the U87.

 

[Khron]

Are you planning to make the gerber file available for free use or sell it so that I can order a PCB of your version on Aliexpress?

Do none of the mounting holes on the ORS87-Plus on PCBway fit your intended mic body?

 

[Juan Vargas]

I just check the link and I don't think this mic body will fit the ORS 87 the V1.1 that they do have the link to order on PCBWay


oh by the way I don't sell things I just do for personal use and learning new things, OK, so if you have that mic body then measure with the vernier caliper you have top screws distance in millimeters then the metal frame width then front top screws to the last screw mounting also how long the PCB can be with that frame there are other option to fastening the tiny transformer PCB openings but for the mic body I have only I can use the NTE10-3 from Mouser the Ali one will not fit the mic body I have not sure about your mic body you got that one look like a really nice heavy duty mic shell

 

[Khron]

I just check the link and I don't think this mic body will fit the ORS 87 the V1.1 that they do have the link to order on PCBWay

Do none of the mounting holes on the ORS87-Plus on PCBway fit your intended mic body?

It helps if you read (all of) what is actually written, not what you might imagine is written...

 

[Korablev]

Do none of the mounting holes on the ORS87-Plus on PCBway fit your intended mic body?

Suitable. Can be secured with ties, but. PCBway services are unfortunately not available in my country.

 

[Korablev]

I just check the link and I don't think this mic body will fit the ORS 87 the V1.1 that they do have the link to order on PCBWay


oh by the way I don't sell things I just do for personal use and learning new things, OK, so if you have that mic body then measure with the vernier caliper you have top screws distance in millimeters then the metal frame width then front top screws to the last screw mounting also how long the PCB can be with that frame there are other option to fastening the tiny transformer PCB openings but for the mic body I have only I can use the NTE10-3 from Mouser the Ali one will not fit the mic body I have not sure about your mic body you got that one look like a really nice heavy duty mic shell

The dimensions between the holes are 28mm x 80mm. And I will order the same transformer as you: NTE10/3, Audio Transformers / Signal Transformers 1:3:10 MIC. https://www.chipdip.ru/product0/8004895384
I can redraw the board according to your drawing, but my main specialty is 3D modeling, I work in Rnino 3D, and I do not really understand the programs for developing printed circuit boards. But if necessary, I will figure it out. Just why, if you have a 1 in 1 layout suitable for my case. In other words, I would be grateful.

 

[homero.leal]

hi guys at the moment I got this layout that will fit into this cheapo Temu mic that please don't laugh at the tiny PCB , ok so I add an opening for the NTE10-3 transformer that can be secure with zip ties the PCB size will fit only on this type of body that looks like those real Telefunken microphones body style I want it to add this data here so the screws mounting for the frame top PCB fastening are about 28.5 mm wide the next screws down are about 28 mm and from this screw mounts down is about 52 mm PCB size is 37 mm x 90 mm I'm gonna continue checking the layout to make sure that there are no bugs I've been doing this for many years but there is always one "oh no I forgot to..." you know what I mean the only thing different that I add to the layout is another R* so to combine different value resistors after FET is adjusted and get the trim pot resistance value to R* final value good day guys

​

Congrats Juan, great work!!!

Quick question: Is the capsule of the TF22 a real LDC? From the pictures, it seems to be an electret.

Just wondering...

Cheers! Keep up the good work!

HL