living sounds
Well-known member
Surely. I does look that your faux 193 circuit is much closer to the U87 circuit from the get go.
OPEN SOURCE DIY Mic Project - ORS 87 - Stripped Down u87
- Thread starter Wordsushi
- Start date
Help Support GroupDIY Audio Forum:
If you’re looking for a cheap way to get a U87 and only care about cardiod and don’t use the PAD or HPF, you can easily breadboard the basic circuit. Here’s one I built into an HL-95 “U87” body. I already had a single-sided Russian (AEG) K67 capsule and a cinemag 2480 laying around, so this cost me about $50 in parts (including the body). Sounds pretty good.
Last edited:
Oooh, great idea. That would be extremely cool, actually. I'd really love to give that a try. Do you have a BOM and schematic for this? And, could I bother you to post a pic of the backside of the board? I've always wanted to do something like this, but my previous attempts to just lay out a simple circuit on a strip board have resulted in crushing disappointment.
I'll do you one better. Here's the layout:
"X1/P-" at the bottom means "XLR Pin 1 and transformer Primary -." You can figure out the rest. The blue line is just used to show that it doesn't intersect the gray lines it crosses. All touching gray lines do connect.
Here's the BOM. Part names somewhat match the original U87 schematic for reference. Tweak to taste:
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)
Tie the XLR Pin 1 to the ground tab on the XLR connector. Film caps should be at least 63V. Use teflon-insulated pins for the capsule connections and keep those junctions "in the air." The board needs to be about 38mmx80mm. Careful not to short to the rails (I used electrical tape to insulate behind the board). Any K67/K87 type capsule should work. Any 8:1 through 12:1 OT should work.
Experiment!
Last edited:
DUDE! Wow, I can't thank you enough. As a project, I think this would be really fun and informative to build. I'm fairly certain I already have a good many of these parts on hand. I'm going to order another HL-95 today. Thank you!
A few other notes:
1) As @Khron would probably point out, the backplate connection (BP at the top) isn't actually a high impedance connection, so you don't really need a teflon insulated pin. I just personally find it easier to make the capsule connections to pins. Feel free to omit that one, but still use one for the front diaphragm connection (FD).
2) R7 doesn't have to be 1G if you can't find it. Anything down to a few hundred Meg is probably fine.
3) There's no rule saying C7 needs to be a big film cap. A tantalum or even electrolytic would work too.
4) This is a fairly forgiving circuit to experiment with. Don't concentrate too much on getting the exact values of any of these parts (other than closely matching R18 & R19).
5) Don't forget to bias up the FET by adjusting R10 for lowest distortion! I'm a fan of using a spectrum analyzer (or an EQ plugin with a spectral view), and dialing things in for the greatest fundamental (i.e., 1kHz if that's the signal you're injecting), and the lowest harmonics. For me, that works better than the 'oscilloscope technique,' since it can be hard to judge the symmetry of a sine wave. To each their own though.
1) As @Khron would probably point out, the backplate connection (BP at the top) isn't actually a high impedance connection, so you don't really need a teflon insulated pin. I just personally find it easier to make the capsule connections to pins. Feel free to omit that one, but still use one for the front diaphragm connection (FD).
2) R7 doesn't have to be 1G if you can't find it. Anything down to a few hundred Meg is probably fine.
3) There's no rule saying C7 needs to be a big film cap. A tantalum or even electrolytic would work too.
4) This is a fairly forgiving circuit to experiment with. Don't concentrate too much on getting the exact values of any of these parts (other than closely matching R18 & R19).
5) Don't forget to bias up the FET by adjusting R10 for lowest distortion! I'm a fan of using a spectrum analyzer (or an EQ plugin with a spectral view), and dialing things in for the greatest fundamental (i.e., 1kHz if that's the signal you're injecting), and the lowest harmonics. For me, that works better than the 'oscilloscope technique,' since it can be hard to judge the symmetry of a sine wave. To each their own though.
Last edited:
Thank you for the additional notes. Quick question. What kind of capsule polarization are you getting?
It should be a little under 48V. There’s no DC-DC converter in this circuit (pre-AI style), so that’s as high as it can go.
A Truly Wonderfull and Happy communist Society - replicates anything from the decadent "west"
The ones I was referring to can be found all over Ali, like this one.
https://www.aliexpress.us/item/3256805119695769.html?channel=twinner
It's a whole mic, but the guts are crap and the shockmount and cable are trash so you just toss all that after you gut the shell.
Just make sure whichever one you buy has an all metal body. There are a few of these that look identical that are all plastic.
I opted for something bigger than the u89, it's closer to the u87, it's a complete set, maybe it sounds like a bm800, I'm not interested. I could modify the stock circuit to do something decent, of course with a proper capsule, but I'm not wasting my time on nonsense. In the 2nd second I emptied his bowels. It is ready to host something of quality. It is cheap and has the shape I wanted.
The body is metal not plastic with massive chunks of metal inside to fool buyers.
https://a.aliexpress.com/_EvvThYl
Attachments
-
Screenshot_2024-03-13-16-30-20-237_com.alibaba.aliexpresshd.jpg -
Screenshot_2024-03-13-16-30-09-372_com.alibaba.aliexpresshd.jpg -
IMG_20240313_162526.jpg -
IMG_20240313_162455.jpg -
IMG_20240313_162246.jpg -
IMG_20240313_161836.jpg -
IMG_20240313_161506.jpg -
IMG_20240313_161311.jpg -
IMG_20240313_160909.jpg -
IMG_20240313_160836.jpg -
IMG_20240313_160648.jpg -
IMG_20240313_160553.jpg
Last edited:
Thanks, guys.
Yeah, I found this one (https://www.aliexpress.us/item/3256805913085041.html) that doesn't specify metal or plastic, and it specifies large diaphragm in the pictures, but small diaphragm in the specs. Suffice to say, there were some unhappy buyers in the comments haha. Not only is it small diaphragm and all plastic, but...see attached pic that was uploaded by one buyer.
Yeah, I found this one (https://www.aliexpress.us/item/3256805913085041.html) that doesn't specify metal or plastic, and it specifies large diaphragm in the pictures, but small diaphragm in the specs. Suffice to say, there were some unhappy buyers in the comments haha. Not only is it small diaphragm and all plastic, but...see attached pic that was uploaded by one buyer.
Attachments
Avoid it is a plastic garbage with a piece of metal to make it seem heavier and made of metal. Shameless lies.
Of course! I was posting it as proof of what you guys were warning against
That's what our group aims to help. It is already full of fakes everywhere, even in reputable stores.Of course! I was posting it as proof of what you guys were warning against
Money talks.
rock soderstrom
Tour de France
The essence of professional studio condenser microphone!
That's my favorite. Reduce it to the max!
I laughed so hard when I saw it. They took the term “capsule on a wire” too literallyThe essence of professional studio condenser microphone!
ubxf
Well-known member
Thank you so much for sharing this layout. are the components between the capsule and R7 housed in the head basket on a different board ?
