DC Servos and Digitally-Controlled Microphone Preamplifiers

DC Servos and Digitally-Controlled Microphone Preamplifiers (509k)
by Gary Hebert, CTO That Corporation
AES Convention Paper 9198, 137th Convention, October 2014

Microphone preamplifiers for professional audio applications require a very wide range of gain and low noise in order to provide a high-quality interface with the vast number of available microphones. In many modern systems the preamplifier gain is controlled indirectly via a digital interface in discrete steps. Often dc servo amplifiers are employed as a means of keeping the dc gain fixed to avoid large changes in output offset voltage while the audio band gain is varied. The resulting highpass filter response varies substantially as a function of the preamplifier gain. We investigate the frequency and time-domain effects of this. We also investigate several approaches to minimize these effects.

Gary’s Convention Paper (#9198) and many other technical papers of note are available from the AES E-Library.