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

[Juan Vargas]

hi guys I'm posting this data of the layout I was afraid that you guys think that I'm a "lunatic " but I say why not right? a measure the mic body that I got again and I was able to fit the layout ones again I still gonna put together the first board anyway but here how it looks now also I add an extra option of resistor R7 Mouser 580-MHR0422SA108F70 20.42 mm PD but still has the macro for a regular resistor and I laid down the D1 and no I'm not crazy good day

 

[Khron]

hi guys I'm posting this data of the layout

I understood why the two sizes; i was "only" asking why two of each size would be needed...

I see my question remains unanswered... Once again I'll say, my problem/question was NOT about why there were two different sizes for the teflon pins, but why there were two PAIRS

 

[Juan Vargas]

only one is need it right for the SGNL? anyway on the first PCB the extra holes I can use them to feed the capsule wires now that the extra option is not really need it let just leave it like that Khron

 

[ZHOUJUN]

I bought a set of U87AI circuit boards, and a set of brass bodies, including all the switch accessories, and a replica transformer. I haven't received the goods yet. This is what the seller showed me. They are very cheap, less than 200 US dollars in total. I want to experiment and install a Neumann K87 capsule. I don't know how much difference it will have with the real U87AI.

 

[Korablev]

Recently received the boards that I ordered from Chinese comrades here:
https://aliexpress.ru/item/10050075...l.0.0.1ace4aa66dWHla&sku_id=12000041381203745
Excellent quality of manufacture! This is not an advertisement.
And once again many thanks to comrade Juan Vargas for providing the Gerber files!
Now I will wait for a scattering of separately ordered parts to begin assembly. I will definitely report the results here.

 

[Екатерина]

I bought a set of U87AI circuit boards, and a set of brass bodies, including all the switch accessories, and a replica transformer. I haven't received the goods yet. This is what the seller showed me. They are very cheap, less than 200 US dollars in total. I want to experiment and install a Neumann K87 capsule. I don't know how much difference it will have with the real U87AI.

I have tried that transformer, and there is a big difference between it and Neumann. The frequency band is narrower and it attenuates more at high frequencies

 

[ZHOUJUN]

I have tried that transformer, and there is a big difference between it and Neumann. The frequency band is narrower and it attenuates more at high frequencies

Is that so? I haven't got it yet, I will test the detailed parameters, to be honest, I don't have high expectations for it, because I have tried many low-priced transformers, and few of them meet the performance standards.

 

[micolas]

I have tried that transformer, and there is a big difference between it and Neumann. The frequency band is narrower and it attenuates more at high frequencies

If this transformer attenuates the high frequencies, then it is ideal for cheap capsules with exaggerated highs. It will take over some of the task of the de-emphasis circuit
'The end justifies the means'
We are the DIY guys

 

[micolas]

@Екатерина did you measure its transformation ratio?​

Does the core seem to have more nickel or is it another alloy?

 

[Екатерина]

Is that so? I haven't got it yet, I will test the detailed parameters, to be honest, I don't have high expectations for it, because I have tried many low-priced transformers, and few of them meet the performance standards.
View attachment 143085
Yes, it looks like this. There is some attenuation in both high and low frequencies

@Екатерина did you measure its transformation ratio?​

Does the core seem to have more nickel or is it another alloy?

I'm sorry, I can't confirm the nickel content as I don't have the relevant equipment，It has a frequency response attenuation of over 6dB in the range of 20-20KHz, which has lost my interest. I think this may be an adjustment made to attenuate high frequencies. Please forgive this translator, as it may seem confusing

 

[micolas]

I'm sorry, I can't confirm the nickel content as I don't have the relevant equipment，It has a frequency response attenuation of over 6dB in the range of 20-20KHz, which has lost my interest. I think this may be an adjustment made to attenuate high frequencies. Please forgive this translator, as it may seem confusing

Ekaterina, don't worry, I also use an online translator that always hijacks the context of messages, especially in technical language, ha ha!
And I think that the attenuation produced by the transformer is intended to tame the exaggerated highs. In fact, this transformer is manufactured by Desheng, which has a lot of experience in the field of electronics.
http://www.zgdes.com/product/908.html

 

[ZHOUJUN]

I'm sorry, I can't confirm the nickel content as I don't have the relevant equipment，It has a frequency response attenuation of over 6dB in the range of 20-20KHz, which has lost my interest. I think this may be an adjustment made to attenuate high frequencies. Please forgive this translator, as it may seem confusing

Cheap capsules produce harsh high frequencies that cannot be leveled with a transformer, and some capsules even remove the high frequencies altogether.

 

[micolas]

Cheap capsules produce harsh high frequencies that cannot be leveled with a transformer, and some capsules even remove the high frequencies altogether.

Not all cheap capsules have the same FR. On the contrary, there is a large dispersion of parameters. So we don't generalize, some cheap capsules have a pretty good FR shape in the 3-5kHz area where sibilance, harsh etc. are produced more frequently (which depend on the sound sources, voices), but they only have exaggerations in the higher highs. Let's just mention the 797 and Takstar capsules, which have more air than the Neumann.
I use with good results some Chinese transformers in the 87 topology, through a steeper Deemphasis only in the upper trebles.
Example: cts-2 from p420
@kingkorg 's research confirms the ATK measurements I have high confidence in.

 

[Juan Vargas]

Recently received the boards that I ordered from Chinese comrades here:
https://aliexpress.ru/item/10050075...l.0.0.1ace4aa66dWHla&sku_id=12000041381203745
Excellent quality of manufacture! This is not an advertisement.
And once again many thanks to comrade Juan Vargas for providing the Gerber files!
Now I will wait for a scattering of separately ordered parts to begin assembly. I will definitely report the results here.

amazing Korablev hey the pads for the transformer wires I just notice that on my PCB might be a little small is ok I also order one more time the boards for the other mic body I place temporally the PCB to the other body with zip ties and it doesn't look that bad at all

 

[Juan Vargas]

hi guys is about R7 the 1GΩ I was reading throughout this section ORS 87 and OneRoomStudio mention that R7 doesn't need to be exactly 1GΩ one just of a hundred of MΩ, a 500MΩ will do?

 

[Voyager10]

It will work, the main difference will be more low-frequency noise from the circuit.

 

[micolas]

@Juan Vargas
Why don't you try to find out for yourself? Test different values. Put 2Gogm or other values.
If experiments don't make you happy, then it's cheaper just to read different threads.

 

[Juan Vargas]

@Juan Vargas
Why don't you try to find out for yourself? Test different values. Put 2Gogm or other values.
If experiments don't make you happy, then it's cheaper just to read different threads.

thanks micolas I will do just that, experiment using this resistor is a 1 G Ohms

 

[micolas]

thanks micolas I will do just that, experiment using this resistor is a 1 G Ohms

¡Sí, señor!
That's the DIY spirit. Experiment as much as you can and enjoy!

 

[Khron]

thanks micolas I will do just that, experiment using this resistor is a 1 G Ohms

I just hope those humongous things fit inside that mic body...