Page 1 of 2 1 2 LastLast
Results 1 to 10 of 11

Thread: testing phantom power delivery

  1. #1
    Join Date
    Feb 2009
    Location
    northampton uk home of Dr Who and Blackstar Amps!
    Posts
    11,255
    Thanks
    1
    Thanked 838 Times in 796 Posts
    Rep Power
    9647194

    testing phantom power delivery

    Sign in to disable this ad
    As promised over in Annyloggy...

    The specification for phantom power is that it should deliver up to 10mA total current from the two "legs".

    This does NOT mean you will measure 48V with a 10mA load. To test 48V you will need..

    1) Voltmeter (with resistance measurement if possible i.e. almost any $30+ DMM)

    2) Two 6,800 (aka 6k8) 1% resistors*

    3) XLR 3 male plug

    4) Soldering kit.

    The 6k8s are soldered to pins 2 and 3 of the plug and the other ends both go to pin one. Leave the wires full length.

    Plug into mixer, tape, whatever and clip meter across a 6k8. Power up. You should read 24volts across the resistor. If so this indicates that the circuit can deliver at least 7.6mA and that is enough for almost any capacitor microphone.

    Now clip meter across pins 2 and 3. Ideally zero but a few mV indicates the lack of matching of the internal 6k8s (but see *) . Poor matching here will reduce PSU noise rejection but is rarely a problem.

    If you wanted to check for the full 10mA you need a 1k4 load (2x 2k8) when you would get 14V across it but I doubt any modern mic would need anything close to ten mills?

    *Buy a rake of resistors, cheap enough! Go through them and find the best match. Does not matter if they are "off" 6k8 a bit (you can use Ohms law to check the error but spook juice really is not that critical) what matters is that they are as close in value as possible.

    Dave.
    Last edited by Steenamaroo; 10-21-2016 at 23:09. Reason: typo

  2. #2
    Join Date
    Dec 2002
    Location
    Massachusetts
    Age
    72
    Posts
    4,652
    Thanks
    13
    Thanked 250 Times in 231 Posts
    Rep Power
    10181460
    Perhaps suggest checking voltage across both resistors to ensure approximately equal voltage on both legs.
    "Plug into mixer, tape, whatever and clip meter across a 6k8." Implies just measuring one(?)

    This setup might a good test of a questionable cable also by plugging the test jiggy into the end of a cable.

    Good write up Dave. Helpful for someone who wants to check phantom and gives some hands on practice at soldering.

    My most power hungry mic is a CAD M179.......

    cad-m179-jpg
    Last edited by arcaxis; 10-22-2016 at 06:40. Reason: was correction for original post which is now fixed
    Mark.......

  3. #3
    Join Date
    Feb 2009
    Location
    northampton uk home of Dr Who and Blackstar Amps!
    Posts
    11,255
    Thanks
    1
    Thanked 838 Times in 796 Posts
    Rep Power
    9647194
    Thanks for the nice comment Mark. I cannot see where my original text is unclear or lacking?

    Perhaps you could 'splain it to this medd'ed up, one eyed old man?

    Dave.

  4. #4
    Join Date
    Nov 2012
    Posts
    2,942
    Thanks
    21
    Thanked 350 Times in 314 Posts
    Rep Power
    5771718
    Quote Originally Posted by ecc83 View Post
    I cannot see where my original text is unclear or lacking?
    There's only three pins, but you've got us soldering to pin 4, and leaving pin 2 N/C.

  5. #5
    Join Date
    Mar 2010
    Location
    Boulder, CO
    Posts
    8,391
    Thanks
    32
    Thanked 602 Times in 557 Posts
    Rep Power
    14820464
    I thought 14mA was the standard current capacity of phantom power.

  6. #6
    Join Date
    Feb 2009
    Location
    northampton uk home of Dr Who and Blackstar Amps!
    Posts
    11,255
    Thanks
    1
    Thanked 838 Times in 796 Posts
    Rep Power
    9647194
    Quote Originally Posted by ashcat_lt View Post
    There's only three pins, but you've got us soldering to pin 4, and leaving pin 2 N/C.
    Oh ***T! WHAT a place for a typo!

    Where jugetthat from BSG?

    Dvae.

  7. #7
    Join Date
    Aug 2005
    Location
    U.K.
    Age
    35
    Posts
    19,928
    Thanks
    1,248
    Thanked 1,103 Times in 978 Posts
    Rep Power
    1000000
    Hey Dave,
    You want me to edit that in, since it's an contribution post?

    People may not read past post one.
    ---------- Steenaudio Website ----------

  8. #8
    Join Date
    Feb 2009
    Location
    northampton uk home of Dr Who and Blackstar Amps!
    Posts
    11,255
    Thanks
    1
    Thanked 838 Times in 796 Posts
    Rep Power
    9647194
    Quote Originally Posted by Steenamaroo View Post
    Hey Dave,
    You want me to edit that in, since it's an contribution post?

    People may not read past post one.
    Please do mate!

    Dave.

  9. #9
    Join Date
    Aug 2005
    Location
    U.K.
    Age
    35
    Posts
    19,928
    Thanks
    1,248
    Thanked 1,103 Times in 978 Posts
    Rep Power
    1000000
    Done.
    Thanks for the informative post.
    ---------- Steenaudio Website ----------

  10. #10
    Join Date
    Mar 2010
    Location
    Boulder, CO
    Posts
    8,391
    Thanks
    32
    Thanked 602 Times in 557 Posts
    Rep Power
    14820464
    Quote Originally Posted by ecc83 View Post
    Where jugetthat from BSG?
    I heard it somewhere and it stuck. I must have trusted the source. I've also read that the maximum allowable draw, according to IEC, is 10mA. If the supply is required to produce up to 14mA then it should never run short of current. Google doesn't turn up much other than an Apogee statement that all their mic inputs with phantom provide 14.1mA and a Shure page that indicates that one of their mic pres should do 7mA per pin.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Replies: 3
    Last Post: 07-25-2013, 19:31
  2. Help needed testing my Phantom power
    By RogerL. in forum Microphones
    Replies: 2
    Last Post: 09-24-2012, 09:12
  3. phantom power on non phantom power mics?
    By seismetr0n in forum Microphones
    Replies: 15
    Last Post: 10-20-2005, 09:05
  4. Testing Phantom Power
    By whyseye in forum The Rack
    Replies: 19
    Last Post: 03-08-2005, 10:54
  5. Phantom Power testing.
    By chernman in forum Microphones
    Replies: 4
    Last Post: 04-20-2001, 06:31

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •