U87 without switches

[joakimkarlthomas]

Hi!

Im building a U87 clone with the DanyB pcb. I was going to build it without the switches psb as my old ADK A51 thats going to contribute as donor body didn't have switches. I was unsure if the switches pcb etc would fit.

So is this possible? Can I just leave the OMN-CRD-8 and LC and PAD as they are on the PCB?

Also, does it affect the trim pot calibration with the multimeter or is it still 11 - 11,5 V dc I should trim in?

 

[Christopher L]

I have built 3 without the switch pcb.  Included in the parts bill of materials is a 3 pole tab. To use the different capsule patterns you must jump two of the poles together to get omni or figure 8. I believe unjumpered is cardioid.
Making holes in a mic body for the switches would probably be tricky.  People have done it though .

You will have to calibrate the mic after it is built. Chunger's build thread will help.  It is very detailed.

Hope this helps

 

[joakimkarlthomas]

Thanks a lot!

I finished the microphone and I've got signal. But also a noise, low frequency. Like a ground noise or something.

I left everything associated to the switch alone as they were on the pcb, as cardioid is fine with me. Can leaving to switch make this noise?

Also found the following on http://www.vintagemicrophonepcbkit.com/Neumann%20U87%20Build.htm:
"The smaller board gets populated next.  Note that only one leg of R7 gets placed in the through hole of the PCB.  The other end gets attached to the isolating pin that goes in the hole labeled “g”.  Also notice that the cap next to the isolating pin has a leg attached to the isolating pin as well and not the through hole."

I didn't do this as it wasn't described on my guide. I also have v1.2 of the pcb, not the 1.3 as on the link above. Should I do this? the 1.2 doesn't look the same, but I guess it's possible? Don't have another isolation pin, can I do it without just solder to the hole?

Thanks in advance!
/J

 

[joakimkarlthomas]

The noise/hum gets worse in some positions. Like near the audio interface and the audio interface USB cable. Also gets worse when I unplug my power supply to my laptop. But, even in the best position in the room the noise/hum is still there but much lower in volume.

 

[homero.leal]

Have you placed the circuit inside the metallic mic body/case?

Mic body acts as a "faraday cage", preventing RF noise affecting the circuit.

First time i built a U87, I was very concerned by this "humming" noise, but after assembing the mic inside the mic body and basket, the problem was gone.

Regards!

HL

 

[joakimkarlthomas]

Haha, yes!

Only tried it with the body on, not the head basket (the capsule didn't fit in it, but that's also fixed now) and didn't think the basket would make any difference. But it did! The mic works great now!

Thanks!
/J