Power Supplies in Mic Preamplifiers

Darren Chan

Darren Chan


People may neglect the importance of a good power supply in their audio equipment. Power supplies actually play a pivotal role in creating an amplified sound that is transparent and defined.

Mic Preamplifier PSU

There are three sources of power required for most solid-state Microphone Preamplifiers:


  1. Dual Rail supply for the actual amplification
  2. 48V Phantom to power condenser mics
  3. Auxillary supply for metering & controls

Dual Rail Supply

The Dual Rail Supply gives power to op-amps (Operational Amplifiers) which perform the job of increasing the gain of a microphone or direct input of up to around 60 dB. Since this is where most of the sonic characteristic of the preamp comes from, it’s important that the performance of the Dual Rail Supply should be considered.


Most consumer power supplies, like the ones found in phone chargers, are not designed for audio, due to the large amounts of noise due to the lack of filtering. Noisy power supplies can increase the noise floor of the preamp. In some cases, even spurious or single-tone buzzing can be heard, such as in the case for the Midas L10, a 500 Series Rack, which uses a noisy switching power supply with inadequate filtering.

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