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

[micolas]

While I'm still waiting for my boards to arrive; I've also ordered the baifeili 87 capsule, HL-95 body, and a shockmount from aliexpress, but I assume the HL-95 body is not going to arrive with any sort of XLR connector.

I'm assuming this one will be the best XLR connector for our purposes: Amphenol Audio AC4-MIC

Any other suggestions or recommendations? I saw a switchcraft QG5M as a similar option but $15 for an XLR connector seems silly

Still, getting good sound at a fraction of the price of a U87 is very tempting

 

[Khron]

While I'm still waiting for my boards to arrive; I've also ordered the baifeili 87 capsule, HL-95 body, and a shockmount from aliexpress, but I assume the HL-95 body is not going to arrive with any sort of XLR connector.

I'm assuming this one will be the best XLR connector for our purposes: Amphenol Audio AC4-MIC

Any other suggestions or recommendations? I saw a switchcraft QG5M as a similar option but $15 for an XLR connector seems silly

Any reason you're looking at a FOUR-pin (or FIVE-pin) XLR insert?

 

[cello4u]

https://groupdiy.com/threads/open-source-diy-mic-project-ors-87-stripped-down-u87.86814/post-1144040

That should be a pretty comprehensive bill-of-materials. Maybe attach a photo of the board so we can verify the component designators vs the values? I'm not gonna spend even more time digging through the rest of this thread for that

Yes, I believe that is where I got the BOM,

I have a puzzle: why do you mind the drawing of PCB v1.1, red and blue paths/traces? Ignore them, they are on the PCB , just focus on the correct positioning of the components. Have the circuit diagram for help.

wasn't sure if they should be touching, or under the other side of the board?

 

[micolas]

Any reason you're looking at a FOUR-pin (or FIVE-pin) XLR insert?

Maybe a dual build like @Wordsushi did.

 

[untamedfrontier]

Any reason you're looking at a FOUR-pin (or FIVE-pin) XLR insert?

Was mainly just looking for any compatible XLR insert, and this one is the only one I saw on mouser that looked appropriate, I didn't even notice the additional pin... I would have been really kicking myself when that showed up.

Will edit and strikethrough that one in the previous post as to not potentially lead any others astray.

AC3-MIC appears to be the right part

Neutrik 3MC-I is also a similar standard XLR connector

 

[micolas]

wasn't sure if they should be touching, or under the other side of the board?

It is a 2-layer, 2-sided PCB.
The red pcb paths/traces are independent of the blue ones.

There are complex circuits that required PCBs with dozens of overlapping layers.

 

[oran.outan]

Hi All,

thanks for all the share about that project !
I just start a build on the V1 version/PCB and I'm confused about the R8 resistor which is in parallel with the Trimpot... I understand that the 4K7 value was for simulation ! That mean on the PCB I need to keep it empty ! The R8 place is if I want to replace the trimpot value by a fix resistor/value ! right ?

thanks for the clarification...
0-0

 

[Khron]

That mean on the PCB I need to keep it empty ! The R8 place is if I want to replace the trimpot value by a fix resistor/value ! right ?

Indeed

 

[micolas]

@oran.outan
You got it right. Just be aware that the value of R8 at the end will not be 4.7kohm, but will be dependent on the Idss of the jFET and how you will make its BIAS.

 

[joulupukki]

Does anyone have any particular components they like for this build?
Is there any specific part, or brand for this BOM you'd recommend based upon it's quality, or price? Or both?

Here, for reference is the ORS 87 BOM, as originally posted by @OneRoomStudio .

R7: 1G
R8: 1M
R9: 7k3
R10: 25K Trimmer
R12: 47k
R13: 330k
R14: 10k
R15: 300k
R16: 56k (for 24V zener, try 47k for 33V zener)
R18 & R19: 2k2 (closely matched!)

C5: 33n (can go as big as 330n if you want more low-end)
C6: 220p (treble cap - smaller = more treble, bigger = darker)
C7: 1u (can tweak to taste. smaller = less bass)
C8: 20u 6v
C9: 470n
C10: 4u7 35V
C11: 4u7 63V
C12: 10u 63V
C13: 10n

Q1: 2N3819

GR1: 1N4749A (24V zener - can try 33V instead with smaller R16)

I'm currently thinking there are 3 ways to approach this build.

1. Use whatever you have on hand.
Make a mic out of scraps and whatever bits and pieces you have laying around, augment with a few specific parts you have to purchase. This probably applies to a lot of folks here who have a collection of spare parts.

2. Find the cheapest way
Purchase everything with the lowest amount of spend possible. I think you could easily put one together with under $100 in total cost, but don't ask me for any specifics on that yet.

3. Go big.
Premium parts. Good capsule. Recognized transformer. See how good you can make it sound.

Am I understanding this right, that with a 2N3819 you could use a 33V zener and get more headroom? I’m curious if this same type of thing would apply to the standard U87 build. Like, could I modify the Dany Bouchard U87 build keeping the same FET but with a 33V zener and get more headroom out of that thing? That’s my only real complaint, especially after modding an AKG P420 and having it turn out so similar but with a lot more headroom. Haven’t yet built an ORS87 version, but maybe this is one thing I could adapt from the ORS87 project.

 

[Khron]

Da, veți avea mai mult spațiu, mai mult semnal de ieșire și transformatorul se va satura puțin mai repede.
Doar puneți un Zenner de 33v și reduceți rezistența care îl alimentează (de exemplu în ORS87 R16 - 22...33kohm , trebuie să experimentați, Zenner-ul se va stabiliza eficient dacă îl alimentați cu câțiva volți în plus, țineți cont și de posibila abatere a tensiunii Phantom +/- 4v). Pentru Dani B. U87 inspiră-te din U87ai.

Forgot to re-translate?

 

[micolas]

Am I understanding this right, that with a 2N3819 you could use a 33V zener and get more headroom? I’m curious if this same type of thing would apply to the standard U87 build. Like, could I modify the Dany Bouchard U87 build keeping the same FET but with a 33V zener and get more headroom out of that thing? That’s my only real complaint, especially after modding an AKG P420 and having it turn out so similar but with a lot more headroom. Haven’t yet built an ORS87 version, but maybe this is one thing I could adapt from the ORS87 project.

Yes, you will have more headroom, more signal output and the transformer will saturate a little faster.
Just put a 33v Zenner and reduce the resistance that feeds it (for example in ORS87 R16 - 22...33kohm , you have to experiment, the Zenner will stabilize effectively if you feed it with a few extra volts, also take into account the possible phantom voltage deviation +/- 4v). For Dani B. U87 get inspired by U87ai.

 

[micolas]

Forgot to re-translate?

Yes,Sir!!!It's complicated on a smartphone to do things right, look for schemes, etc

 

[joulupukki]

Yes, you will have more headroom, more signal output and the transformer will saturate a little faster.
Just put a 33v Zenner and reduce the resistance that feeds it (for example in ORS87 R16 - 22...33kohm , you have to experiment, the Zenner will stabilize effectively if you feed it with a few extra volts, also take into account the possible phantom voltage deviation +/- 4v). For Dani B. U87 get inspired by U87ai.

Excellent, thank you for confirming! I’ll do some experimenting after I finish up with another experiment (changing the Bassman Micro tube amp I built to use a pair of EL84 power tubes instead – won’t be “micro” anymore once I’m finished).

 

[oran.outan]

@oran.outan
You got it right. Just be aware that the value of R8 at the end will not be 4.7kohm, but will be dependent on the Idss of the jFET and how you will make its BIAS.

Yes yes! This part was clear…
Thanks

 

[micolas]

Yes yes! This part was clear…
Thanks

There are many ways to BIAS the jFET.
Depending on the measurement equipment available (DMM, oscilloscope, signal generator, spectrum analyzer - hardware or software), depending on the purpose pursued, preferences (cleaner or more saturated sound),maximum signal with reasonable distortion, symmetrical half-sines, by ear with injection of complex musical audio signal, with sine signal, with high-level voice, etc., using equipment to visualize / measure the waveform, harmonic distortion (some prefer more 2nd order harmonic, which is supposed to make the sound more musical) etc etc
In general, opinions, preferences, tastes are divided, so BIAS is a purely personal decision, it is actually a compromise.
Many years when I was building guitar effects pedals, We considered that asymmetric clipping/saturation/distortion was closer to the character of tubes, so I used in overdrive,distorsion,fuzz etc, --many types of diodes (germanium, silicon, selenium), LEDs(of different colors and sizes) and junctions of different bipolar or mosfet transistors, connected anti-parallel. So it's possible that asymmetric distortions will produce a special sound in microphones.
In any case, from my personal experience, I can say that among the transistors, jFETs are the closest in sound to tubes.

Useful information about jFET's BIAS:
https://groupdiy.com/threads/neumann-vintage-u87-clone-build-thread.48030/

 

[elskardio]

I just finished the big brother! I went with the UTM0587 for this one.

 

[Whoops]

the 'Ali' U87ai sounds identical to the 'real thing'...

It has the same exact circuit, it’s very well done, so there’s no reason to not sound the same.
It sounds incredibly good even without the tunning

Thank you so much for the tunning tips Ruud

 

[cello4u]

No C12 on the 1.1 ORS 87 board?

 

[Khron]

No C12 on the 1.1 ORS 87 board?

What does C12 do?