U87 (Revision A) in BM800 microphone donor body

[c1184701]

yes they do. but you isolate them via the teflon part. the hole in the pcb fits the teflon ring leading to no contact to the pcb. top and bottom part are conducting, but no contact to the pcb is there as the teflon parts isolates.

Great thanks! The holes in my pcbs were a bit too small to fit the teflon part in, so I carefully widened them with a small pointed file.

I'm still hunting for the large value resistors: 33M, 68M, 220M and 1Gohm. Has anyone found a good source for these recently?

 

[Khron]

Mouser?

 

[c1184701]

Mouser?

They're out of stock of 1Gohm until the end of March, unless I pay £7 per resistor. And they don't stock 220M at all other than in SMD.

 

[Khron]

The 1G situation is unfortunate, but they stock cheap(ish) 300M:

https://www.mouser.fi/ProductDetail...GAEpiMZZMtlubZbdhIBIIy58CNicjAufEvJr%2BQyf4k=
150M:

https://www.mouser.fi/ProductDetail...=sGAEpiMZZMtlubZbdhIBIOuVybmxT4vsMQb0qMKhxS8=
... Unless there's a particular reason that ONLY 220M works. Which i seriously doubt (and no, "that's what's in the original schematic" is not a valid technical reason imho).

 

[c1184701]

The 1G situation is unfortunate, but they stock cheap(ish) 300M:

https://www.mouser.fi/ProductDetail...GAEpiMZZMtlubZbdhIBIIy58CNicjAufEvJr%2BQyf4k=
150M:

https://www.mouser.fi/ProductDetail...=sGAEpiMZZMtlubZbdhIBIOuVybmxT4vsMQb0qMKhxS8=
... Unless there's a particular reason that ONLY 220M works. Which i seriously doubt (and no, "that's what's in the original schematic" is not a valid technical reason imho).

Thanks for the suggestions!

I should mention that I am getting my projects mixed up. I'm building two U87 and two U47fet both from @mihi_fuchs pcbs. The 220M is part of the pad in the U47fet, so perhaps the value isn't critical as you suggest.

 

[Khron]

If anything, you might want to keep the relative ratios of those resistors, and tweak the capacitor values to match whatever corner frequencies are involved(?).

(... Although my hunch is that those resistors are there just to minimize the DC charge across those capacitors and thus minimize switching pops; the capacitors themselves are doing the actual attenuation, in fact, pretty much like in the KM84.)

 

[kuhruby]

Do you still have PCBs? I'd like to buy sets for 2 builds if you do. @mihi_fuchs

 

[mihi_fuchs]

Do you still have PCBs? I'd like to buy sets for 2 builds if you do. @mihi_fuchs

still availyable - sent you a PM

 

[kuhruby]

Hey guys. I'm in the process of gathering all the parts for a couple of these. I'm not bad with a soldering iron but I'm not too familiar with the technical side of things. I've seen some other builds where they recommend consistent solder joints, and also to clean the board very well after finishing the soldering because not doing so will introduce noise. I've seen a video of a popular one, the pimped alice, where he uses soap and water to clean the PCB after soldering, and then sticking it in the oven for a bit. Is that something that is necessary with this build? Also, which capsules do you recommend, I'm in the US if that means anything in terms of availability or budget. Speaking of, are there any budget capsules that will work well, or will that defeat the purpose of this build? Thanks

 

[komikuapples]

Finished my one the other day. Such a fun build! My first mic project ever. Hopefully the first of many to come.
Really appreciate Michael’s work on this and he’s a super friendly and helpful guy.

I chose a Maiku K87 capsule and a 3U Audio transformer.
Made a version of the capsule holder to fit a Maiku capsule with the BM-700. Lowered it a bit as well. If anyone wants the STL file just let me know.

The mic sounds great! Not very bright (which seems to be the case from what I’ve read reg. Maiku) but takes EQ really well.

Would love the files if you're willing to hand them out

 

[komikuapples]

@mihi_fuchs
Could I buy a PCB? I'm located in the US and can't sign up for the site in the market area.

 

[mihi_fuchs]

@mihi_fuchs
Could I buy a PCB? I'm located in the US and can't sign up for the site in the market area.

I still got some left. If you‘re in the US there may be additional custom duties to pay …

For the rest see the PM I‘ve sent

Cheers
Michael

 

[antocu]

Hey guys. I'm in the process of gathering all the parts for a couple of these. I'm not bad with a soldering iron but I'm not too familiar with the technical side of things. I've seen some other builds where they recommend consistent solder joints, and also to clean the board very well after finishing the soldering because not doing so will introduce noise. I've seen a video of a popular one, the pimped alice, where he uses soap and water to clean the PCB after soldering, and then sticking it in the oven for a bit. Is that something that is necessary with this build? Also, which capsules do you recommend, I'm in the US if that means anything in terms of availability or budget. Speaking of, are there any budget capsules that will work well, or will that defeat the purpose of this build? Thanks

Here you can find some good info about soldering
If i were in the US I'd try the Jli capsule you can find it here TSC-2
Never tried out for my build as I'm from Italy and shipping makes it inconvenient, but they're not so expensive so worth a try in my opinion if you are in the US.

About the cleaning process, I didn't wash the pcb as you see in the video you mentioned, I've just used some Isoprophyl alchool on a towel and a toothbrush, or cotton fioc for the HiZ junction, and the mic is incredibly silent.

One thing I receltly implemented are a pair of 22nF caps at the XLR, as I was having some RF noise.. now it works perfectly.

 

[komikuapples]

One thing I receltly implemented are a pair of 22nF caps at the XLR, as I was having some RF noise.. now it works perfectly.

Can you show me where this was done? Which pins?



Also, is it safe to assume the on-board switches could be wired to actual mic body switches with no modifications?

 

[mihi_fuchs]

Can you show me where this was done? Which pins?



Also, is it safe to assume the on-board switches could be wired to actual mic body switches with no modifications?

Hi,

Each of the audio pins is connected to the ground pin by 22 nf (hope i‘m right and that’s how antocu did it???). Neverteheless there are already 2 x 330 pf on board doing exactly this (somewhere on p. 1 you find the schematics). So maybe check before the mod and if you find it necessary add them to the pins.


For the switches - you‘re absolutely right - that‘s possible of course.

Best regards,
Michael

 

[antocu]

Hi,

Each of the audio pins is connected to the ground pin by 22 nf (hope i‘m right and that’s how antocu did it???). Neverteheless there are already 2 x 330 pf on board doing exactly this (somewhere on p. 1 you find the schematics). So maybe check before the mod and if you find it necessary add them to the pins.


For the switches - you‘re absolutely right - that‘s possible of course.

Best regards,
Michael

Yes I added the 22nF caps between pin3 to GND (pin1), and between pin2 and GND, directly on the xlr connector. And I confirm the switches works very well, I added them too

 

[oongbac]

This is great! I used 3u audio K87. I gave anothet PCB to my friend, so I think I should order some more if it is still available.

Thank you for this great project @mihi_fuchs !!

 

[grobaesthet]

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

 

[grobaesthet]

still availyable - sent you a PM

Hi,
unfortunately I am not able to PM you as I did not post enough to unlock this feature.
Is there still a PCB left?
I would be interested to buy it.
All the best
Simon

 

[mihi_fuchs]

Hi,
unfortunately I am not able to PM you as I did not post enough to unlock this feature.
Is there still a PCB left?
I would be interested to buy it.
All

Hi! Yes there are still some left. I PM you ... hope that works for you ...
Cheers
Michael