U87 (Revision A) in BM800 microphone donor body

[mihi_fuchs]

Hi,
your U87 mod looks very good!

But regardiung the U87 I have the following question:
Is there a possibility to make a "stripped down" U87? I just need the "kidney"-pattern, no pad or filter.
Maybe this could not only make the PCB a little lighter but also get lost of anything that degrades the sound?
A few years ago I tried this on my own with an U87(rev A) schematic but never finished the project.
Perhabs your PCB allows to leave out a few traces or just jumper them?
Thanks in advance and all the best,
Simon

Hi Simon,

I'm sure you can omit these parts. But except 2 styros and one gohm resistor you do not safe on a lot of high valuable parts. And even those are just a few euros. So from the financial part I do not think it makes a lot of sense.

Nevertheless, if you argue with the audio path, that may be true. I did not hear that these switching options degraded the sound significantly, but ears are different, and my ears are old and a bit degraded by a lot of concerts ;-) - so you may be right (btw - very funny/interesting thread in this forum about ears at different ages ;-) )

you can definitely jumper the switches hardwired omiting the pin/jumper option. you can for sure then omit a few parts - I would need to dig into the schematics more carefully to check out which ones exactly but for sure R2, SW1, C1, SW2, SW3, R5 and C5. On the DC-DC converter part you can omit for sure C22, D22, D24, and C24.

I hope I got all parts right, but I'm pretty sure that's what you can omit by leaving out the switching options.

However you still need to wire the switch-footprints accordingly to the cardiod position (see building guide).

Hope that helps a bit figuring out the options ...

Best regards,
Michael

 

[grobaesthet]

Hi Simon,

I'm sure you can omit these parts. But except 2 styros and one gohm resistor you do not safe on a lot of high valuable parts. And even those are just a few euros. So from the financial part I do not think it makes a lot of sense.

Nevertheless, if you argue with the audio path, that may be true. I did not hear that these switching options degraded the sound significantly, but ears are different, and my ears are old and a bit degraded by a lot of concerts ;-) - so you may be right (btw - very funny/interesting thread in this forum about ears at different ages ;-) )

you can definitely jumper the switches hardwired omiting the pin/jumper option. you can for sure then omit a few parts - I would need to dig into the schematics more carefully to check out which ones exactly but for sure R2, SW1, C1, SW2, SW3, R5 and C5. On the DC-DC converter part you can omit for sure C22, D22, D24, and C24.

I hope I got all parts right, but I'm pretty sure that's what you can omit by leaving out the switching options.

However you still need to wire the switch-footprints accordingly to the cardiod position (see building guide).

Hope that helps a bit figuring out the options ...

Best regards,
Michael

Hi Michael,

thank you very much for your fast and detailed answer!

My question about omitting parts of the schematics are indeed not because of financial regards.
And I would not say, that my ears are very good and can in any way hear the difference of a signal passing a switch.
It really is about simplifying and using less parts. Because in my experience, less parts means less stress

As soon as I have your PCBs and some time for the project, I will figure out the necessity of the parts you mentioned in the last post.
If I have any questions I would be happy to ask them in this thread. And as soon as my "stripped down version" of your Schematic is finished and working, I can provide you and other interested viewers with details of the changes in the PCBs.

Thanks for your efforts and all the best!
Simon

 

[papadajoke]

Greetings, mihi_fuchs. Is it possible to get pcb's for your U87 and U47?

 

[RuudNL]

Funny that the U87ai schematic (especially the DC converter) is an exact copy of the Mic&Mod U87 kit.
Even the non-critical components have the same value. Also the choice of a 47 nF or 100 nF capacitor is surprising. What a coincidence... (Especially because the Mic&Mod U87 kit was introduced years ago and was designed by me!)

 

[Migs 31]

Funny that the U87ai schematic (especially the DC converter) is an exact copy of the Mic&Mod U87 kit.
Even the non-critical components have the same value. Also the choice of a 47 nF or 100 nF capacitor is surprising. What a coincidence...

I think it's Mic & Mod who copied a few designs from GDIY members and somewhere else.
Some people here got really peeved about that in the past.

Anyway Mihi_fuchs, good job on this.


M

 

[RuudNL]

I think it's Mic & Mod who copied a few designs from GDIY members and somewhere else.
Some people here got really peeved about that in the past.

Anyway Mihi_fuchs, good job on this.


M

I'm afraid it is the other way round...
As you can read in post #84, is was me who designed the Mic&Mod U87 kit.
I suppose they won't be amused. I will inform them about this.

 

[Migs 31]

I'm afraid it is the other way round...
As you can read in post #84, is was me who designed the Mic&Mod U87 kit.
I suppose they won't be amused. I will inform them about this.

I have a lot of respect for your work, knowledge & contributions here @RuudNL
My observation was that indeed M&M have in the past come under the spot light.

Their U67 looks very similar to one of your designs ?!? Am I wrong?
Or did you authorised them to do so?

Anyway take the necessary measures to address the issue.
Good luck.

M

 

[RuudNL]

Yes, the 'U67' is exactly my design.
As far as I understood, mihi_fuchs can expect legal action from Mic&Mod...

LINK

 

[mihi_fuchs]

Yes, the 'U67' is exactly my design.
As far as I understood, mihi_fuchs can expect legal action from Mic&Mod...

LINK

as far as i got it me and fabian (mic and mod) had it talked out. your dc-dc conv. is off the thread - i‘ll remodel and that‘s it. btw, claiming the ip for the schoeps dc-dc converter is a bit far fetched.

so bit calming down on all ends … the schoeps dc-dc circuit is pretty close to a lot designs - commercial ones and others …

so, thanks for getting me and fabian together to talk it out, before legal action is required … was actually a quite nice and respectful mailing … so, i cannot say a bad word about mic and mod thus far …

as said - thanks for bringing the sides together …

cheers
michael

 

[mihi_fuchs]

So finally I got back answer from Fabian. He was very busy and it was important to me that he had enough time to review all information and schematics we provided:

Mic and Mod was provided with the following information (2nd of may):

as it took to be honest a Sunday morning (2 hours) to redesign the DC-DC unit, it was more time to redraw the schematics. We - as now clearly stated went with a DC-DC-design posted as open project here - the two hours we spent breadboarding to get another set of values. All links has been adopted in the initial thread.

Here is the all information provided to Fabian regarding IP:

"Regarding the DC-DC-converter:

Following mics have the same circuit:

MXL 603S - http://recordinghacks.com/microphones/MXL/603S (released 2000)

Schoeps CMC5 - http://recordinghacks.com/microphones/Schoeps/CMC-5 (released 1973)

Gefell MT71S - http://recordinghacks.com/microphones/Microtech-Gefell/MT-71-S (release unknown, schematics say 1994)

It is a quite basic schematic. As stated despite Schoeps had it adopted for microphones, Baxandall had the schematics already published in 1959 (see Paper attached).

But nevertheless, I went with the design depicted in the link below, resembling the crucial parts of the DCDC-conversion according to the Schoeps mic and adoptions. The link below was posted as open project on the Forum 2017, so two years before you released your schematics. Of course values have been breadboarded here once more, so there is no problem again.

https://groupdiy.com/threads/open-source-project-little-oscillator-pcbs-for-ldcs-shared-on-osh-park.65174/"

In addition the DCDC-converter has been going to open project thread (schematics and values). Just feel free to use those values.

I also informed Fabian - who has been buying the designs from Ruud (all current Mic And Mod Designs are Ruud’s) - that the residual PCBs will be privately sold (8th of may).

Fabian replied that he does not see a problem from his side (15th of may).

So therefore the remaining PCBs from the initial order are going back to the black market. Please use the BOM V4 or higher (all old PCBs are fully compatible with the new BOM).

Despite all these facts, I have to say that all Mailing from Fabian's side was extremely professional and respectful. Just as it should be.

Happy here that we have worked everything out.

All the best,
Cheers
Michael

 

[mihi_fuchs]

just to make sure the DCDC converter change does not affect the mic:

I had two mics: mic1 is with the old DCDC-converter, mic2 is once with the old and once with the new DCDC-conversion. I just ran both vs. of mic 2 against mic1 with white noise and inverted phase. The files are provided here.

 

[noizetoys]

Just saw this video:



Congrats!

A pretty good endorsement!

 

[mihi_fuchs]

Just saw this video:



Congrats!

A pretty good endorsement!

Hi noizetoys,

thanks, but - as mentioned above - the alterations to circuit are based on knowledge from that forum. that does not really reflect in the video.

the dcdc conversion is an alteration of an open source project here - therefore we posted it in addition there.

the cap adjustment of low frequencies is common knowledge around here …

and the circuit is and resembles the original (audio path).

and in addition, the boards offered are the ones from the initial order … so once sold, i do not know if i will do another batch.

so, despite that - it got a really nice built and i‘m happy here with the clones.

and 99% is marks voice - loved his character voices once i checked it out. He‚s REALLY good in what he does. and had a pretty good fight in getting the mics to work.

anyway, thanks but take the above into account,
best regards,
Michael

 

[lpkyer]

Hi noizetoys,

thanks, but - as mentioned above - the alterations to circuit are based on knowledge from that forum. that does not really reflect in the video.

the dcdc conversion is an alteration of an open source project here - therefore we posted it in addition there.

the cap adjustment of low frequencies is common knowledge around here …

and the circuit is and resembles the original (audio path).

and in addition, the boards offered are the ones from the initial order … so once sold, i do not know if i will do another batch.

so, despite that - it got a really nice built and i‘m happy here with the clones.

and 99% is marks voice - loved his character voices once i checked it out. He‚s REALLY good in what he does. and had a pretty good fight in getting the mics to work.

anyway, thanks but take the above into account,
best regards,
Michael

Hello Michael
Where can I buy your pcb ? Cheers

 

[TadS]

Nice to meet you all.
I have been deeply inspired by this thread and am planning to create my own DIY microphone, gathering the necessary components.
However, I have limited knowledge of electronic components. Can you please advise if it's okay to choose capacitors C1, C2, and C3 other than polyethylene capacitors?
I believe polyethylene capacitors offer excellent sound quality, but I'm hesitating due to the $50 shipping cost for them to cross the Pacific Ocean.

 

[mrgrooves666]

You could use MLCC or film (WIMA/PET)

 

[TadS]

You could use MLCC or film (WIMA/PET)

I'm glad to hear that. I want to prioritize assembling using readily available parts. Thank you.

 

[AviEinZur]

@mihi_fuchs
Hello Michael, thank you very much for this project. I would like to buy 2 sets of U87 pcb and capacitor kits. If you can send me a PM with payment options, I can't send you a PM for some reason.
Edit: and also please one set of U47fet and capacitor kit.

Thank you very much,

Avi.

 

[TadS]

Hi, mates.
I finally complete the microphone for this project.

It was actually a somewhat challenging journey, starting with mimicking Mr. Fuchs' PCB based on circuit diagrams and images. The layout differs from the original PCB.
I even paid $90 to a professional engineer to design it because I was so passionate about making this microphone. And this is just for my personal use.

There were issues along the way, such as misaligned transformer mounting holes and parts that couldn't be used to connect the two PCBs, but I tackled these problems in a very "analog" way.
Regarding the parts, some of them were unavailable in the BOM, so my mouse scurried around local online shops and auctions.

As for the body of the BM800 from Aliexpress, I don't mind the basket distortion, but the screws for the PCB were too long, causing the wiring inside to float like a spring. So, I had to force it into the case using an analog method.
I didn't have a fitting XLR on hand, so I obtained one from a junk cable. However, the screw wouldn't fit into the body's hole, so I had to use a chopstick-made wood chip to secure it forcibly.

I chose the 797 audio capsule. The accuracy of the capsule mount wasn't perfect, but it didn't bother me. I'm also eagerly awaiting the arrival of the arienne audio capsule.

After some difficulties, I finally detected 60V and 10.5V and took out a beer from the fridge.
My first impression is that it sounds really good and close to S87 of microphone parts. The benefits of the transformer and 60V will become clearer with more use.
The BM800 body is very compact and convenient. I also have hopes for the acoustic effects of the small basket.

Yes, l really love this microphone.

Thank you
TS

 

[MicMaven]

Hi, mates.
I finally complete the microphone for this project.

but I tackled these problems in a very "analog" way. ... ...I had to force it into the case using an analog method.

Does "analog way" involve using a hammer, or hacksaw, or .... any large power tool? James