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Behringer Xenyx 502 phantom power mod

Discussion in 'Electronic Repair Modifications DIY' started by MEGADRIVE Jeroi, Sep 14, 2012.

  1. MEGADRIVE Jeroi

    MEGADRIVE Jeroi Active Member

    While this is very good mixer for vocals recording on DAW then models before 2009 package update "Now with Phantom Power" lack phantom power for condenser mics on XLR connector.

    DISCLAIMER:
    - If you don't know how to open the mixer or know how to solder then STOP and find a new hobby. I am not responsible if you get electric shock or burn your house etc.

    MODDING 502 FOR 24V PHANTOM POWER:

    Only some condenser mics like Shure stage vocal mics works with 11-52V phantom. Some true condenser mics don't work and they require 48V ±something. Look your mic datasheet if it supports less than 48V. I am looking to mod my 502 with full 48V phantom also with integrated 60hz filter so this is not fully complete mod yet but provides 24V for some mics as it when singing karaoke or recording to DAW. You can filter 60HZ in DAW if you like but I am still trying to filter 60hz noise off so stay tuned.

    There are 2 DC input pins which both have 24v DC. My Shure SM86 condenser mic specs said that it can use 11-56V phantom power so 24V is sufficient for my needs and I believe for most on stage vocal condenser mics while some expensive true condenser studio mics won't.

    1. Pick up about 5-10 3k3 resistors. You need the match 2 resistors with multimeter that they are exactly same values for 0.01 accuracy.
    2. Solder matched resistors into 24v pin.
    3. Wire second ends to XLR pin2 and pin3

    Here is photo of how to solder resistors:

    View attachment 4865

    4. Add some electric tape under the soldering legs and wrap them all with second layer of electric tape on top.

    Voila! Your 502 is now modified with 24V phantom power.

    Current on 2 and 3 pin are from 3k1 to 6k8 from 7.9mA to 3,4mA where Behringer specs say that phantom with 48V uses 6k8 and current 7.9mA on resistors. I used on this photo couple matched 6k8 resistors and current is 3,4mA on the pins. My mic sm68 mic works fine.

    Note: Your phantom power is always on so if you need option to disable phantom power, you need to make hole to backside of the case and insert switch between 24v pin and resistor legs. Also you need 400uF to 1000uF 50V elco on switch output leg to resistors to smooth out the voltage spike and cradually start upping the voltage to 24V in 5 time scales. This wil filter the voltage spike as elco wil need to streghten the voltage in 5 time cycles and cannot output voltage spikes at all. WHat happens is when you switch your phantom on you will have smooth open. While you turn your phantom off the condenser will provide some voltage until it drains off so you will get smooth delayed voltage drop also.

    Note2: It is better to use 3K3 resistors to have 7.6mA current because atleast my SM68 manual says current drain is about 5,4mA so I am changing in some day if I need or not the resistors to provide more current. Don't know tho if I need to replace as the mic sounds nice and my current speakers cannot handle any greater loudness that the mic + mixer is providing.
     

    Attached Files:

  2. Zilus

    Zilus Active Member

    Very, very nice mod!
     
  3. MEGADRIVE Jeroi

    MEGADRIVE Jeroi Active Member

    Not best yet. It needs ground loop isolation as quite high ground loop problem atm. Can anymody suggest good resonant filter for 24v to reduce 60hz out or lower than 120h out?
     
  4. RemyRAD

    RemyRAD Guest

    Is that 24 V from a regulated supply or from an unregulated supply? You need a regulated supply.

    And it's not true that most condenser microphones can run from 11-56 volts. That is only applicable to permanently polarized electret condenser capsules. All real condenser microphones require 48 V to polarize the capsule. Nothing less will do with classic true condenser microphones. So while you can install your own phantom power for electret condenser microphones. It's only for electret condenser microphones. It's not for true condenser microphones requiring a full 48 V, such as Neumann's all the way down to cheap Taiwanese made Nady's which all require a full 48 V feed/supply.

    So don't be confusing people by telling them your mod will be sufficient for any condenser microphone. It's not! So that's really inferior information you have supplied everybody with. Understandable perhaps, but not good.

    Yeah, almost any microphone power supply for phantom power needs to be clean regulated power. And then you shouldn't have any problems with Ho hum. And for instance my old Radio Shaft Pressure Zone Microphones. Never and I mean never worked properly, when you tried to power them from phantom, without hum, even from a regulated supply designed for that specific application. So you are not correct sir. Not by a long shot. Most any electret condenser microphone can be powered from a single AA penlight battery. And that's all that some should be powered by.

    I just love lousy information.
    Mx. Remy Ann David
     
  5. MEGADRIVE Jeroi

    MEGADRIVE Jeroi Active Member

    I just watched some Neumans technical sheets and they work just fine with 24V. Most of them said voltage source comply aes42 and they need 11V phantom power. Like I said most condenser mics work with 24V, while there may be some unique models that will not. It's up to you to look the technical information of the mic.

    Hence for same reason your condenser mic works with battery albeit it is not designed to use on stage. And for the same reason I added note that 3k3 is better resistor than 6k8 in this setup as it provides 7.6mA rather when 6k8 provides 3.5mA. Neuman's some models spesific said that any phantom source which at least provide 3-3.4mA of current on pins. So 6k8 resistor here meets the spec just but in order to achieve greater performance going above 7mA is good where most phantom sourced provide 7.0mA of current on pins. Actually the voltage does not be that much of issue with condenser mics as they work usually with wide area of voltages, but it is the current that generates magnetic fields and more current, more fields, more greater pickup to some degree.

    To meet 48V phantom spec: 48V/6k8 = 7.05 mA. Where 24/3k3 = 7.27mA. If there would be 3k4 resistors you would get about same current drain.

    And while you still argue I am going to look and get fully 48V phantom but it needs both 24V pins to produce 48V but need to look more about those after the power regulators on board, since last time I did not take regulators heat sink off so could not get to poke with multimeter to there.
     
  6. RemyRAD

    RemyRAD Guest

    I don't care that you think you saw Neumann guys doing something with 24 V. Yeah, ± 24 volts because every non-polarized condenser capsule ever made, requires a minimum of 48. Only electret condenser capsules can work because they have a permanent polarity charge. So they can work on most any DC voltage. When you deplete the voltage on a non-polarized condenser capsule, you get garbage. You like garbage? I don't. And Neumann doesn't offer any electret condenser microphones. Now they might be installing some voltage doublers in some of their newer microphones? They cost enough to do that. Which could take 24 and convert it to 48.

    This feels like a cat fight?

    Where have you gotten your information from?
    Mx. Remy Ann David
     
  7. MEGADRIVE Jeroi

    MEGADRIVE Jeroi Active Member

    No, some Neumann models spesify that they use 48V ±4V and needs atleast of 3mA current drain. Those models may not work with 24V but I don't have those models to test with. But in most condenser technology the 48V is not must because the Voltage is not critical to produce good magnetic field, to calculate magnetic field means that more current, more greater magnetic field. And my information is from school. I study Electronics engineering in second grade and we had last year end project a metal finder and we needed to study a lot of magnetic fields. Most good metal finder use only 12V to produce 40cm pickup. This is very closely in same area than microphones take advantage of magnetic fields to generate variable AC. But you may be right with those models that say in datasheet as working voltage 48V ±1-something V. But this argue is not important for me as I am going to take a look of 48V added to 502 and will change the mod to meet Neuman and rest studio grade microphones support. At least I must change the resistors if not good method to get 48V. How ever this is not the biggest issue. The issue is 60hz noise when using phantom. How ever it does not matter when listening music and singing but the noise in DAW is what to take a look. I am adding some inductance and capacitanse to my circuit and take a look if I can filter 60hz noise before it is induced to amplifiers of the mixer.
     
  8. Boswell

    Boswell Moderator Distinguished Member

    If you look in your textbooks you will find that capacitor ("condenser") microphones do not use magnetic fields, they use electrostatic fields. As Remy said, some condenser microphones (the electret type) utilize a permanently-charged backplate, and these need phantom power only to power the impedance converter output buffer. This type will usually run from around 12V up to the maximum PP voltage of 52V. Other types, like conventional Neumanns, use the phantom power to generate the electrostatic field directly, and this type needs the full 48V nominal. Some older high-end designs actually use an internal voltage-doubler or tripler circuit to generate 96V or around 120V in order to use a higher spacing between the diaphragms.
     
  9. RemyRAD

    RemyRAD Guest

    I have a pair of scientific B & K, " electret " condenser microphones designed for sound pressure levels up to 148 DB (no pad circuit needed). And I believe it utilizes a 147 V power supply, not for the condenser element, but for the internal electronics on the inside of this +20 pound, telephone pole mounted, outdoor microphone. Strangely enough, when you remove all of the weatherproof enclosure, you find the same capsule that you find on the studio series microphones, they also produce. The only actual difference in the capsule is only a molecule or so thick, quartz crystal protective coating on the diaphragm. The microphone was actually designed to measure the loudness levels of military ordinance explosions and overflying jets. And they aren't something that can be mounted on a microphone stand. I just stick them on a pair of chairs and leaning the capsule in the general direction, where I need it. These would actually require a heavy steel pipe, custom made stand, each. Though I've thought about also trying to adapt tripod speaker stands? But the diameter of those aluminum pipes are too large. And you also have to have 110 V, AC power cords going to each one. Nothing very phantom about that, LOL. I keep them in a large canvas, military style, duffel bag, because they won't fit into any convenient commercial suitcases. They are 4 feet long each. Stainless steel neck tube. Pretty damned intimidating to look at. Even more intimidating to pick up. And something that won't break when falling off of a 100 foot tall telephone pole, LMAO. Great for death metal recording since one of these microphones can actually kill somebody.

    [Police Report: Cause Of Death, heavy-metal microphone.].
    Mx. Remy Ann David
     

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