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

[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

 

[Juan Vargas]

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

hi homero I think it is electret , oh thank you

 

[Juan Vargas]

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.

oh ok ok so 28 mm top then bottom 80 mm for screw mountings, I can then adjusted to fit that, how much PCB length you can have on this mic body you got there or better say how long it can be? the width and the length take your time that is what I'm doing making sure all is correct you can do JLCPCB? I order from them many times

 

[Korablev]

oh ok ok so 28 mm top then bottom 80 mm for screw mountings, I can then adjusted to fit that, how much PCB length you can have on this mic body you got there or better say how long it can be? the width and the length take your time that is what I'm doing making sure all is correct you can do JLCPCB? I order from them many times

Thank you for your help. I measured more precisely. And quickly drew a 3D model of the HL-95 microphone. If someone is going to buy this case, it is sold here: https://aliexpress.ru/item/10050064...l.0.0.16244aa6VfUE5X&sku_id=12000037309239239

The thing is that the most convenient board manufacturing for me would be the NextPCB service https://aliexpress.ru/item/10050075...st.14.15c44aa6ARFKy8&sku_id=12000041381203745

But the Chinese manufacturer asks for a Gerber file.

JLCPCB is available to me through intermediaries with a headache, and I think it will take a very long time.

Could you share your gerber file? It doesn't even require any changes, our landing places and free space inside the cases coincided amazingly.

 

[Juan Vargas]

I'm glad that I brainstormed this a bit more if the transformer is installed with zip ties then how the other two wires will find a path? on the image "middle one" of the transformer has the zip ties and the example of the 3 wires what I did is to add more holes so the wire can then find it place

 

[Juan Vargas]

Thank you for your help. I measured more precisely. And quickly drew a 3D model of the HL-95 microphone. If someone is going to buy this case, it is sold here: https://aliexpress.ru/item/10050064...l.0.0.16244aa6VfUE5X&sku_id=12000037309239239

The thing is that the most convenient board manufacturing for me would be the NextPCB service https://aliexpress.ru/item/10050075...st.14.15c44aa6ARFKy8&sku_id=12000041381203745

But the Chinese manufacturer asks for a Gerber file.

JLCPCB is available to me through intermediaries with a headache, and I think it will take a very long time.

Could you share your gerber file? It doesn't even require any changes, our landing places and free space inside the cases coincided amazingly.

this is really value information you put here nice I can share the gerbers then you can use Sprint Layout 6 to modified if you need to I'm not sure if I'm allow to share links here, ok so top 28.5 mm x 80 mm I see that you can use maybe M3 screws with nuts for fastening, the hole size of the PCB now are 3.00 mm in diameter you notice that I post about the transformer other wire they are 5 of them and I didn't notice the other two or 3 on the other size need to find it patch for the TX? connections so I add more holes so wire can you know be connected

 

[Korablev]

this is really value information you put here nice I can share the gerbers then you can use Sprint Layout 6 to modified if you need to I'm not sure if I'm allow to share links here, ok so top 28.5 mm x 80 mm I see that you can use maybe M3 screws with nuts for fastening, the hole size of the PCB now are 3.00 mm in diameter you notice that I post about the transformer other wire they are 5 of them and I didn't notice the other two or 3 on the other size need to find it patch for the TX? connections so I add more holes so wire can you know be connected

Yes, I have Sprint Layout 6. I think I can figure out how to work with it. Here are my thoughts on NTE10/3, audio converters. Please note that there is a large gap of 2mm around the entire perimeter between the printed circuit board and the transformer. It is possible that additional holes are not needed. Well, as an option, the two lower wires can be soldered from the bottom of the printed circuit board. If you can't post files here, could you send me your project for Sprint Layout 6 to my email? tv-6 dog mail.ru

 

[Juan Vargas]

oh ok you right I will send you the files to your e-mail, ok so the holes are not really need it then?, oh yes you right there is a large gap and wire can be solder under the PCB, I think in my case my mic frame doesn't have not enough space at the bottom, you made the transformer way too tick I think lol I saw a video of a gentlemen that was using this NTE-3 former see image, also if you can check the layout to be sure all is correct I check it many times but a second pair of eyes can also help too let me know if all is in order.

 

[Korablev]

oh ok you right I will send you the files to your e-mail, ok so the holes are not really need it then?, oh yes you right there is a large gap and wire can be solder under the PCB, I think in my case my mic frame doesn't have not enough space at the bottom, you made the transformer way too tick I think lol I saw a video of a gentlemen that was using this NTE-3 former see image, also if you can check the layout to be sure all is correct I check it many times but a second pair of eyes can also help too let me know if all is in order.

Thank you! I'm sure there will be plenty of space in your case, but only if you remove this board.

And here is information on the transformer: https://static.chipdip.ru/lib/759/DOC029759077.pdf

 

[Juan Vargas]

Yes, I have Sprint Layout 6. I think I can figure out how to work with it. Here are my thoughts on NTE10/3, audio converters. Please note that there is a large gap of 2mm around the entire perimeter between the printed circuit board and the transformer. It is possible that additional holes are not needed. Well, as an option, the two lower wires can be soldered from the bottom of the printed circuit board. If you can't post files here, could you send me your project for Sprint Layout 6 to my email? tv-6 dog mail.ru

hi I try to send the file to your e-mail and is not working ? no worries , here are the gerber files please check from schematic to layout to see if all is in order and for what I read here the NTE-3 transformer connections are like this:

TXI- red wire
TXI+ black wire
TX0- yellow wire
TX0+ white wire
on the NTE-3 tiny transformer the blue wire is not in use

the PTFE insulator part number is 534-11154 Mouser the hole diameter is 3.20 mm you can change this one they are other ones,
the orientation of the transformer would be with the 3 wire down and the good thing is that they will align just fine, the gerber files can be imported to Sprint Layout 6 software if you need to do some adjustments to fit the microphone frame you have if need it.

Today adding more information on C7 1uF capacitor the pitch distances are 34.5 mm, 22.5 mm, 10 mm, 5 mm, and the last one 2.54 mm, I add and extra R* so in series you can get the value you need after Q1 FET final adjustment. The electrolytic caps C8,10,12 are 5 mm in diameter size and PD 2.54 mm, the top insulators have two options of part number Mouser# 534-11154 3.18 mm diameter on the PCB the hole is 3.20 mm the other one Mouser# 534-11150 1.90 mm diameter and hole diameter on the PCB are 2.00 mm "I'm not sure how tight they need to be" Korablev there it is

 

[Korablev]

hi I try to send the file to your e-mail and is not working ? no worries , here are the gerber files please check from schematic to layout to see if all is in order and for what I read here the NTE-3 transformer connections are like this:

TXI- red wire
TXI+ black wire
TX0- yellow wire
TX0+ white wire
on the NTE-3 tiny transformer the blue wire is not in use

the PTFE insulator part number is 534-11154 Mouser the hole diameter is 3.20 mm you can change this one they are other ones,
the orientation of the transformer would be with the 3 wire down and the good thing is that they will align just fine, the gerber files can be imported to Sprint Layout 6 software if you need to do some adjustments to fit the microphone frame you have if need it.

Today adding more information on C7 1uF capacitor the pitch distances are 34.5 mm, 22.5 mm, 10 mm, 5 mm, and the last one 2.54 mm, I add and extra R* so in series you can get the value you need after Q1 FET final adjustment. The electrolytic caps C8,10,12 are 5 mm in diameter size and PD 2.54 mm, the top insulators have two options of part number Mouser# 534-11154 3.18 mm diameter on the PCB the hole is 3.20 mm the other one Mouser# 534-11150 1.90 mm diameter and hole diameter on the PCB are 2.00 mm "I'm not sure how tight they need to be" Korablev there it is

Thank you very much Juan Vargas! Today I will order the production of boards from Chinese comrades, as well as those parts that are indicated in the BOM of the project. I will definitely write later about how my assembly of this magnificent ORS 87 project is going. Many thanks to the community for this opportunity. Assembling a microphone with your own hands is wonderful! Juan, if you need help with 3D modeling, be sure to contact me, I will help.

 

[Juan Vargas]

my pleasure! have fun please check layout and schematic make sure all is in order before order good day
by the way C12 is C7 from schematic but I change it the ID to C12 22uF 63V cap

 

[Juan Vargas]

hi guys got a question is a good idea to have one of the PCB support to be connected to microphone GND to chassis? I trace a connection to screw support to P1

 

[rankot]

As an aid to troubleshooting, here's some information about the ORS87-Plus testbed I built.

Schematic​

Here's the schematic with the component values used. The changes from the ORS87+ schematic were mostly to follow the original U87/U87A values more closely.

View attachment 138270

For testing, the U87's 'calibration input' arrangement was rigged up by replacing R15 with 560R + 6K8 in series, and the input wired to the midpoint. (I understand the V1.1 PCB has space for 2 resistors). I didn't implement a pad or bass-cut switch. Feedback capacitor C4 was 2.7pF, made by putting 5pF and 6pF caps in series.

To simulate a single cardioid K87-style capsule, there's a 47pF capacitor (Ccap) connected between the FD and BP inputs (the Neumann test procedure includes a fixture which does exactly this).

The BF256B JFET was chosen after a shootout (here) between various types: it's nearly the best by various measures, and cheap and readily available. Biasing the FET was done by adjusting trimmer R7 for minimum THD at the output, when fed with a 100mV, 1KHz sine wave at the calibration input. Values in blue are DC measurements at the bias point, and in red are the measured AC values.

The input stage looks like this:

View attachment 138271

Results​

Results are pretty close to the reported values for the U87A:

Measurement	Value
Overall gain, CAL to Vout, 1KHz (measured at 100mV in)	-1.6dB (0.83x)
JFET open-loop gain (1KHz)	+19dB (9.0x)
THD, 100mV RMS in, 1KHz	0.013%
Max input voltage. THD < 0.5%, 1KHz (RMS)	530mV
Drain current at optimum bias	0.38mA
Polarization voltage	45.0V

I also did a frequency response and distortion plot using REW. This is with a 100mV RMS input level.

View attachment 138272

We're getting a moderate 3-4dB dropoff at 15KHz, and a stronger rolloff after that. Obviously some of the distortion is coming from the transformer, which is relatively cheap compared to many alternatives.

If I understand this schematic well, you removed high pass and pad switches. What was the purpose of Rh/Ch anyway, since you removed them too?

 

[Juan Vargas]

anyway I add then an extra pad to solder a chassis GND if need it also since I know that measure hole distance with a none digital vernier caliper I change the holes shape so it will have a bit more play

 

[Voyager10]

If I understand this schematic well, you removed high pass and pad switches. What was the purpose of Rh/Ch anyway, since you removed them too?

Do you mean R9 and C5? They are an alternative way of achieving a high-frequency roll-off, instead of the C12/C13/R14/R15 feedback network. Nothing wrong with using them, it's just not how the U87 circuit does it.

 

[Екатерина]

I tried many different transformers from Ali and literally everything is better than T13, only T8 is worse,

the best is bv8, but it is very big

Good day, by a fortuitous coincidence, I acquired the adorable little transformer located on the right side of T13. Have you conducted any measurements on its frequency response?

 

[eso]

I haven't posted on this thread for a bit. This thread sent me off on a serious tangent.

I started off with Homero's board on PCBway, and then picked up khron's boards. I got 3 ORS 87s built and then went off the rails. The picture here is before I installed the Cinemag transformers. Cinemag is a local company that makes great products and I like to support them.

I've since completed a pair of U67 mics and power supplies and am getting started on a pair of U47s with parts on hand for a couple of C12s right behind those. For added fun I'm going point-to-point on these newer projects. I happen to have a friend here that I met 50+ years ago who is pretty well known in the mic world and so I've got some excellent tech back up when I need it.

And the members here are amazing. This is an awesome community and an excellent resouce for those of us who like making things.

I've been looking for a link to order some of the boards Juan Vargas modeled a few pages back that includes the mounting for the transformers. Is there such a link? I'd like to rebuild my U87s with such boards if available.

Thanks all,
eso