DIY Microphone help - quiet output

[moose_loose]

Hi, i ordered a few bits to upgrade a BM800 microphone. I have finished what i think is the correct wiring. But it seems very quiet, if i turn the gain up then there is some buzzing. Is it my use of crappy wires?

The capacitors were between 1-2 and 1-3.

Any help would be greatly appreciated.

Parts list and images:

 

[Khron]

But it seems very quiet, if i turn the gain up then there is some buzzing. Is it my use of crappy wires?

Well, using THE thickest mains wires you could find only makes things mechanically difficult for you, but that in itself should not be likely to be the cause of the quiet output.

Is that the only capsule you have available?

How about some voltage readings? Black probe on ground, red probe on the positive of each of the silver cylindrical capacitors...

 

[moose_loose]

Well, using THE thickest mains wires you could find only makes things mechanically difficult for you, but that in itself should not be likely to be the cause of the quiet output.

Is that the only capsule you have available?

How about some voltage readings? Black probe on ground, red probe on the positive of each of the silver cylindrical capacitors...

Thanks,
Yea i only had this wire or very, very thin wire.
1-20v
2-0.03v
3-20v
4-10.8v
5(top)-0.2v
6(bottom)-0v
7(top)-0v
8(bottom)-0.1v
9-2.8v
10-0v

 

[RuudNL]

2,5 mm2 for audio might be a bit overkill…
What is the voltage between pin 1 and 2 (and pin 1 and 3) on the XLR connector?
Should be 30 Volts or more.

 

[Drosselmeier]

is the body made out of plastic?

 

[moose_loose]

View attachment 135596

is the body made out of plastic?

No it seems to be 20v and the body is plastic yea.

 

[moose_loose]

2,5 mm2 for audio might be a bit overkill…
What is the voltage between pin 1 and 2 (and pin 1 and 3) on the XLR connector?
Should be 30 Volts or more.

It seems to be 20v.
Its running off a 45v preamp, but that is only plugged into usb. Is that normal?
Thanks

 

[Khron]

It seems to be 20v.

That means something is sucking about 8mA, and that's not right...

 

[moose_loose]

That means something is sucking about 8mA, and that's not right...

I soldered BC223 capacitors between 1-2 and 1-3. Could this be the issue?

 

[MicMaven]

the body is plastic yea.

Howdy!

Please humor me a moment. I am a rookie with good intentions ... but then my road to Heck is well paved with all my good intentions!

* Are you testing with the mic cover off? Did you test it with the head basket and body all put together? If not, reassemble and retest.

* What happens if you cover the microphone with aluminum foil? Your plastic body may not provide sufficient electrical shielding - and you have altered the manufacturer's arrangement with your little capacitors and big wires. I am not criticizing, just saying you have changed it in some way to put it outside of its original operating parameters.

* Most BM-800 type microphones are designed to use either or both 48v from a mixer or audio interface AND 8-10v from a traditional computer sound card. That might, maybe, perhaps explain any apparent voltage anomalies ... or not.

* Some guys specify 22nF capacitors for RF suppression. While I am also a rookie mic builder, I kinda always thought a BC233 is a transistor. A web search suggests 233 pF capacitors, so I wonder if you could double check the name and value of the capacitors you are using? The other fellers will give you better advice with reliable info.

* Wild Shot No. 20987 - I sorta wonder, more than suggest, whether the length of your wires have altered the original design just enough to cause buzzing. Short, thin wires make a shorter antenna less prone to capturing stray RF/EMI/TVI etc. Really thin wires are OK for the short distance from the circuit board to the XLR pins - especially considering you are only dealing with mic level signal strength. It might matter more if you were running substantially higher voltage. I am not saying using heavier gauge wires is bad - just saying shorter, thinner wires will likely be sufficient and maybe act less like an RFI antenna. (Well ... I said it is a wild shot, right?)

* Also - What OTHER DEVICES are operating nearby? We recently had a long running discussion about how to squelch cell phone interference on a Takstar CM-60. I sometimes suffer serious RFI in my transceiver when using an external hard drive dock on the desk near the rig. Fluorescent light ballasts and some older LED lights may cause EMI/RFI. Your BM-800's plastic body may not provide adequate shielding.

* I would move the installation to another computer - or clear away (at least turn off) all other devices which could generate EMI/RFI and see if that isolates an external cause.

Just a few wild stabs in the dark. Good luck. James

 

[moose_loose]

Howdy!

Please humor me a moment. I am a rookie with good intentions ... but then my road to Heck is well paved with all my good intentions!

* Are you testing with the mic cover off? Did you test it with the head basket and body all put together? If not, reassemble and retest.

* What happens if you cover the microphone with aluminum foil? Your plastic body may not provide sufficient electrical shielding - and you have altered the manufacturer's arrangement with your little capacitors and big wires. I am not criticizing, just saying you have changed it in some way to put it outside of its original operating parameters.

* Most BM-800 type microphones are designed to use either or both 48v from a mixer or audio interface AND 8-10v from a traditional computer sound card. That might, maybe, perhaps explain any apparent voltage anomalies ... or not.

* Some guys specify 22nF capacitors for RF suppression. While I am also a rookie mic builder, I kinda always thought a BC233 is a transistor. A web search suggests 233 pF capacitors, so I wonder if you could double check the name and value of the capacitors you are using? The other fellers will give you better advice with reliable info.

* Wild Shot No. 20987 - I sorta wonder, more than suggest, whether the length of your wires have altered the original design just enough to cause buzzing. Short, thin wires make a shorter antenna less prone to capturing stray RF/EMI/TVI etc. Really thin wires are OK for the short distance from the circuit board to the XLR pins - especially considering you are only dealing with mic level signal strength. It might matter more if you were running substantially higher voltage. I am not saying using heavier gauge wires is bad - just saying shorter, thinner wires will likely be sufficient and maybe act less like an RFI antenna. (Well ... I said it is a wild shot, right?)

* Also - What OTHER DEVICES are operating nearby? We recently had a long running discussion about how to squelch cell phone interference on a Takstar CM-60. I sometimes suffer serious RFI in my transceiver when using an external hard drive dock on the desk near the rig. Fluorescent light ballasts and some older LED lights may cause EMI/RFI. Your BM-800's plastic body may not provide adequate shielding.

* I would move the installation to another computer - or clear away (at least turn off) all other devices which could generate EMI/RFI and see if that isolates an external cause.

Just a few wild stabs in the dark. Good luck. James

Thank you, i will try all your suggestions.
I was wondering if the metal shielding mesh needed to be grounded. It wasn’t in the original design, but the plastic body isolates it. Foil is a good idea which would bridge the gap.
This is what i bought:
https://www.jlielectronics.com/diy-accessories/capacitors-rf-suppression-pair/
Mayne they sent the wrong part?

 

[MicMaven]

Thank you, i will try all your suggestions.
I was wondering if the metal shielding mesh needed to be grounded. It wasn’t in the original design, but the plastic body isolates it. Foil is a good idea which would bridge the gap.

You might try stripping the ends from a short bit of wire and bridge the gap between head basket and mic ground. Just pinch it in against the head basket or use alligator clips or something. Maybe running a test lead from grille to mic ground - just to see if grounding the basket/grille helps. (I think. Remember I am also a rookie!)

This is what i bought:

https://www.jlielectronics.com/diy-accessories/capacitors-rf-suppression-pair/
Mayne they sent the wrong part?

I believe those are a good choice.

* What if you remove the capacitors? What sort of RF problem do they solve? Are they installed just for safety, or do you suffer specific RFI you need to squelch? If the latter, we may need to adopt other measures.

While these capacitors should work fine business, perhaps you do not need them. Sometimes, for reasons only Murphy (ref. Murphy's Law) knows, adding components to avoid problems can actually cause problems, themselves. It is a bit of a logical paradox, but I follow the old adage, "If you fix something long enough, you will, eventually, break it."

The other fellers will have more likely solutions! Good Luck. James / K8JHR

 

[MicMaven]

Thank you, i will try all your suggestions.

Oh... I forgot to mention the problem MIGHT could maybe possibly be an issue with your cable or its connection the to interface. There have been long discussions on this reflector - and one is raging on another reflector again this very week - concerning proper XLR cable wiring. Web search "pin-1 problem" for a sampling of what this is about - for now it should suffice to check the cable for issues in how it is wired.

Again, you do not say whether it was quiet before you installed the capacitors, or why you installed them, if not as a mere prophylactic hedge just in case, whether you are trying to solve a particular problem. James