Phantom power
Phantom power, in the context of professional audio equipment, is DC electric power equally applied to both signal wires in balanced microphone cables, forming a phantom circuit, to operate microphones that contain active electronic circuitry.Microphone preamplifiers of the Nagra IV-series tape recorders offered this type of powering as an option for many years and Schoeps continued to support "negative phantom" until the CMT series was discontinued in the mid-1970s, but it is obsolete now.The International Electrotechnical Commission Standards Committee's "Multimedia systems – Guide to the recommended characteristics of analogue interfaces to achieve interoperability" (IEC 61938:2018) specifies parameters for microphone phantom power delivery.In part, this is because first-generation (late-1960s through mid-1970s) 48-volt phantom-powered condenser microphones had simple circuitry and required only small amounts of operating current (typically less than 1 mA per microphone), so the phantom supply circuits typically built into recorders, mixers, and preamps of that time were designed on the assumption that this current would be adequate.The specific symptoms vary somewhat, but the most common result will be reduction of the maximum sound pressure level that the microphone can handle without overload (distortion).[7] Equipment damage is also possible if a phantom-powered input connected to an unbalanced dynamic microphone[8] or electronic musical instruments.[11][12] Digital microphones complying with the AES 42 standard may be provided with phantom power at 10 volts, impressed on both audio leads and ground.[citation needed] The method is considered obsolete as power supply noise is added to the output audio signal.[15] Many older Sennheiser and Schoeps microphones use this powering method, although newer recorders and mixers are phasing out this option.This results in a 12-volt potential difference with significant current capability across pins 2 and 3, which would likely cause permanent damage if applied to a dynamic or ribbon microphone.Plug-in-power (PiP) is the low-current 3–5 V supply provided at the microphone jack of some consumer equipment, such as portable recorders and computer sound cards.Phantom power used in this context is 8–16 volts DC in series with a 470 ohm (nominal) resistor as specified in RTCA Inc. standard DO-214.
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