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Battery Phantom Power Noise
Old 3rd January 2019
  #1
Battery Phantom Power Noise

Hello,

Been a bit puzzled by this...I made this 18V phantom power supply:



The Fig 6A one.

Here is the mic I am using:
JTS ( ジェーティーエス ) >CX-500 楽器用コンデンサーマイク 送料無料 | サウンドハウス

(Sorry, the site is in Japanese, but the phantom power requirements say 12~48V.)

I am using it on an acoustic instrument and plug in with a 1/4" instrument jack.

When I first made the power supply, it worked great, powered the mic, quiet, etc. But the problem is that now, it started having a lot of white noise and I am not sure what the problem is.

I changed all the caps and resistors as well as some new wiring, but the noise still persists.

When I plug in the microphone directly into an XLR jack and use the 48V regular phantom power, it's nice and quiet.

Any ideas?
Old 3rd January 2019
  #2
Gear Guru
 
Thomas W. Bethe's Avatar
 
1 Review written
🎧 15 years
You might want to post this in the Cables, connectors forum on GS.
Old 3rd January 2019
  #3
Lives for gear
 
nosebleedaudio's Avatar
 
🎧 15 years
Quote:
Originally Posted by SilentSound ➡️
Hello,

Been a bit puzzled by this...I made this 18V phantom power supply:



The Fig 6A one.

Here is the mic I am using:
JTS ( ジェーティーエス ) >CX-500 楽器用コンデンサーマイク 送料無料 | サウンドハウス

(Sorry, the site is in Japanese, but the phantom power requirements say 12~48V.)

I am using it on an acoustic instrument and plug in with a 1/4" instrument jack.

When I first made the power supply, it worked great, powered the mic, quiet, etc. But the problem is that now, it started having a lot of white noise and I am not sure what the problem is.

I changed all the caps and resistors as well as some new wiring, but the noise still persists.

When I plug in the microphone directly into an XLR jack and use the 48V regular phantom power, it's nice and quiet.

Any ideas?
The specs I saw (English) were 1-5VDC did not mention Phantom..
I would change the resistors to the typical 6.8K 1%, I prefer to match them even closer .01% if I can...or as close as my DVM will go...
Old 3rd January 2019
  #4
nosebleedaudio, I presume you mean replace the 2K resistors with the 6.8K, yes?

I also saw the English site that says 1-5VDC, though not sure if that is accurate since it works with regular 48V phantom through the adapter. I will try and double check it anyway.

Thank you.
Old 5th January 2019
  #5
Thanks, the 6.8K resistors solved the problem. No more noise!

Also did a double check on the phantom voltage. The mic comes with an adapter from XLR to mini-XLR. It looks like the adapter also drops the voltage down to 5V, so from now on I will use a lower voltage. No need for the 18V! I was originally going off the requirement from the Japanese site.
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