Phantom powered microphones with their preamplifier can generate signal from -48 to +48 volt (or 24 or 12), then it run through wire and maybe receiver and reaches ADC. I want to know if 48v signal is attenuated before DAC or directly (with ~48V peak) driving the ADC.

I think it must not be 48v since 48 volt is a constrant of condenser microphone without prepolarization, and there is no need for such a high voltage on ADC. But from other perspective sound have high dynamic range and ADC also need high input voltage dynamic range to achive high SNR for weak signals (since weak audio signals are extremely small because of its logarithmic scale). Then what is the typical voltage P-P range that drives high-end audio ADC?

Here we can see output peak voltage from classical amplifier specified by B&K with their peak voltage mentioned (though these are not phantom standard but the basics must be comply): CCLDandClassic And here we can see some of their preamps with their peak voltage mentioned: variants of preamps


1 Answer 1


Microphones generate signal from -48 to +48 volt ...

No they don't. Phantom powered microphones may be powered at 48 V DC. The audio signal will be 100 mV to 1 V or so and it will be alternating.

I want to know it attenuate before DAC or directly drives the ADC.

You, most likely, will need to boost it for the ADC. If the ADC does not handle negative voltages you will also have to apply a positive bias to the signal to bring it up to half the ADC range.

Then what is the typical voltage P-P that drives high-end audio ADC?

The P-P voltage will be enough to drive the ADC adequately to maximise the signal to noise ratio without ever driving it above or below its maximum or minimum input specification.

  • \$\begingroup\$ Then 48v is just used to polarising specific microphones? And this 1v PP is before or after mic pre amp placed before wire? \$\endgroup\$ Mar 27, 2022 at 13:21
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    \$\begingroup\$ The 48 V (capital 'V' for volt) may be used for polarising condenser microphones but may also be used for pre-amplifiers built into any microphone. You will find details on microphone output levels on their datasheets. \$\endgroup\$
    – Transistor
    Mar 27, 2022 at 13:24
  • \$\begingroup\$ I'm sorry for my wrong words have been used I've changed that and I'm trying to better ask my question. If you can help ask better question I will thank you more. \$\endgroup\$ Mar 27, 2022 at 13:30
  • \$\begingroup\$ Maybe the microphones with p24 p48 must have the specified output peak voltage? Since these (p24 p48) are standards and must be compatible with pxx system, doesn't it? \$\endgroup\$ Mar 27, 2022 at 13:56
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    \$\begingroup\$ @mohammadsdtmnd: the 48 V phantom power only provides power for amplifiers or other circuits in the microphone or other phantom-powered device. The audio signal from a phantom-powered microphone will be similar in level to that from a non-powered microphone. The audio input circuits of a mixing console will not see the 48 V phantom voltage, and won't be able to tell if the signal comes from a passive mic or from a phantom-powered mic. \$\endgroup\$ Mar 27, 2022 at 15:05

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