The introduction of the 48-volt phantom powering circuit in 1966 led to IEC 61938:1996. A key aspect of this powering circuit are the 6.81 k? precision resistors that are in parallel to the emitter-follower of the microphone preamplifier. These resistors act as a load on the emitter-follower that causes added distortion. A new approach is presented whereby, in series of these 6K8 resistors, an electronic circuit is placed that acts as a high input-impedance current source, which does not load the emitter-follower. By making this change, THD is decreased by 10 dB while also slightly improving the gain. Measurement results are presented comparing audio performance of a conventional 48-volt phantom power circuit and this new circuit along with circuit details.
https://www.aes.org/e-lib/browse.cfm?elib=19821
Click to purchase paper as a non-member or login as an AES member. If your company or school subscribes to the E-Library then switch to the institutional version. If you are not an AES member and would like to subscribe to the E-Library then Join the AES!
This paper costs $33 for non-members and is free for AES members and E-Library subscribers.
Learn more about the AES E-Library
Start a discussion about this paper!