Splitting a Mic Signal FOH/Amp

Discussion in 'Amps, Mics & Pickups [DB]' started by anonymous122511, Nov 9, 2011.

  1. anonymous122511

    anonymous122511 Guest

    Dec 28, 2010
    Gathering opinions on how you would send a signal from a condenser mic to an amp and a PA. The obvious and most simple way is to use a Y-cable with the 48v phantom power coming from the FOH console.

    The next option would be to still Y at the mic but use a mic preamp to provide the phantom. Both these choices are pretty straight forward. I prefer the second idea as it makes the mic/amp rig completely independent from the FOH system. An variation would be to send the signal from the preamp rather than from the mic. Not sure if there are advantages one way or the other.

    Now here's where I start to have real questions. I'm thinking of going mic to mic preamp (an FMR Audio RNP) to tuner (that acts as a mute) and splitting the signal here with a Radial JDI. I own all this stuff already so I'm more looking for opinions on the basic principle rather than on specific pieces of the puzzle. Although if you have experienced based opinions on those I'd be a fool not to listen. Part of me says it's big overkill (or worse) to use a DI to send a mic signal to FOH while another part says the mute to tune option is worth exploring.

    Ok, start shooting holes in my boat.
  2. Just a preamp/amp with a DI output? It comes in handy when you can send your signal pre EQ and therefore are able to use the EQ to prevent from feedback on stage.
  3. In professional audio, when a microphone is to feed more than one preamp, this is normally done with a mic splitter that uses an isolation transformer. This ensures that only one source of phantom power reaches your mic (very important!) and helps prevent ground loops, buzzes and hums. If you are going to be working with a large-scale FOH sound system, the sound company may already have appropriate mic splitters.

    Here's an article at the Jensen Transformers web site that explains mic splitting in more detail: http://www.jensen-transformers.com/an/an005.pdf
  4. anonymous122511

    anonymous122511 Guest

    Dec 28, 2010
    Thanks. I wonder if sending the mic to FOH through the JDI wouldn't achieve isolation? I suspect it would...if so problem solved all the way around.
  5. There are two potential issues with what you are proposing: The output signal from the microphone is balanced and must remain so, while the Radial JDI has an unbalanced input. Also the isolation transformer used in a proper mic splitter will have a 1:1 turns ratio (meaning the signal level going out will be about the same as the signal level coming in), while the Radial JDI uses a step-down transformer with a turns ratio of 12:1, which will have a significant loss of signal at the output (about -22dB). There's no substitute for having the right tool for this job, which is a properly designed transformer-isolated mic splitter. Even a relatively inexpensive unit like a Whirlwind or a ProCo is preferable to none at all. Good luck.
  6. anonymous122511

    anonymous122511 Guest

    Dec 28, 2010
    Thanks for your replies, I'm not as educated with this stuff as I should be. The RNP mic preamp has an unbalanced out and lots of headroom that should solve both these issues, no? I understand the right tool for the job and all but if I can make what I already own work....
  7. Ideally the mic should be split right at its output using a proper mic splitter, before it gets to a preamp. This gives the FOH the cleanest direct signal possible unaffected by the gain setting of your mic preamp on stage. Again if you're dealing with a professional sound company, they should have a mic splitter available. However if this your band's PA system, you can take the output of your FMR Audio RNP and connect it to your Radial JDI to give a balanced, mic-level signal to send to the PA. You then loop the RNP output (using the Thru jack on the JDI) to your stage amp.

    Keep in mind that many DB players use a pickup sent their onstage amp and a mic sent (only) to the FOH. This doesn't require a mic splitter or mic preamp onstage, keeping things simple, and makes the most sense to me.
  8. anonymous122511

    anonymous122511 Guest

    Dec 28, 2010
    I'll be using this with house rigs/soundmen and I have a strong feeling I'll be going the simple route and sending the mic directly to FOH and letting them give me a wedge. It seems I do have the capability with what I own to execute a plan B with my amp for a stage monitor though. I think I will invest in a real mic splitter too. It's not in my nature to leave much to chance and showing up with all you need to do what you want never hurts in terms of getting the audio guys on your side.
    Thanks again for sharing your knowledge.
  9. anonymous122511

    anonymous122511 Guest

    Dec 28, 2010
    Just to follow up on this I got a used Radial JS-3 mic splitter at Long & McQuade that does the job a lot better than my original convoluted setup. In retrospect it seems pretty obvious a simple, uncluttered signal path was the was to go. Certainly both the soundmen I've laid this rig on so far have been impressed by the sound and the tidiness of it.
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