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A large-diaphragm condenser mic in a shock mount, its XLR cable glowing orange down to a preamp with the 48V button lit red.
Fundamentals · Novice-friendly · 5 min read

What 48V Phantom Power Does, and Which Inputs Need It

Why condenser mics and active DI boxes need phantom power, why ribbon mics need care, and how to keep a stage box inside its current budget.

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The short answer

Condensers and active DIs need it. Ribbons need protecting from it.

  • Needs 48VCondenser mics and active DI boxes.
  • Doesn’tDynamic mics and passive DIs. Ribbons go on inputs you can switch off.
  • WatchInputs that switch phantom in banks, and each unit’s current budget.

Before you start

Phantom power is 48 volts DC that a preamp sends up the same balanced mic cable the audio comes down. It powers the electronics inside a condenser mic or an active DI box, and it’s switched on at the preamp, not at the mic.

What needs it

Figure 1. The J48 is an active DI and needs phantom power. The JDI is passive and doesn’t.
  • Condenser mics: overheads, acoustic guitar mics, most choir and ambient mics. No phantom, no sound.
  • Active DI boxes: keys, bass and acoustic DIs with electronics inside. Passive DIs don’t need it.
  • Dynamic mics: don’t need it. A dynamic mic on a correctly wired balanced cable isn’t harmed by it.
  • Ribbon mics: don’t need it, and are the ones to protect. A faulty cable, a patch bay or an adapter that unbalances the line can put phantom across the ribbon. Leave it off on any channel a ribbon mic uses.
  • Line-level gear: wireless receivers, playback interfaces and keyboards plugged straight into a preamp don’t need it. Leave it off.

Per input, or in banks

Front panel, drawn by IEM Rig
MIC INPUTSLINE OUTPUTSBEHRINGERS16Digital Stage Box
Behringer S16
Figure 2. The S16 switches 48V per input, so a condenser and a ribbon can sit side by side.

Digital consoles and stage boxes mostly switch phantom per input. The S16, SD16, DL32 and Wing Rack all document 48V switchable per input. Some small mixers and interfaces switch it in groups, which matters when a condenser and a ribbon would share a group. Check your unit’s manual before you plan the patch.

The current budget

Midas DL32Gear page ›
Figure 3. A DL32 has 32 preamps. Spreading condensers across a console and a stage box keeps each unit inside its phantom budget.

Each phantom-powered device draws a few milliamps (the IEC 61938 standard allows a P48 mic up to 10 mA), and a preamp can only supply so much. Many units can’t feed full phantom current on every input at once. The IEM Rig planner checks this for you: it totals the draw of the condenser mics and active DIs wired to each unit against the unit’s documented phantom budget, where the catalog has one, and warns whenever a ribbon mic is wired to an input that can supply phantom.

What it means for the rig

Explore in 3DBehringer X32 RackPhantom on the console and its stage boxes is set from this screen.Gear page ›
  • Put condensers and active DIs on inputs that switch phantom on their own, and ribbons on inputs you can switch off.
  • Spread condensers across a console and a stage box rather than loading one unit.
  • Turn phantom on after the cable is connected and the channel is muted, and off before unplugging.
  • For counting how many inputs you need in the first place, see how many preamps your rig needs.

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Sources

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