Jensen Twin Servo 990 Mic Preamp

Projects > Jensen Twin Servo 990 Mic Preamp

The Twin Servo mic preamp design was published as Jensen application note #83. The design employs Jensen’s transformers as well as the 990C discrete opamp designed by Deane Jensen. (This design is commercially available from the John Hardy Company.)

In app note #83, Jensen warns that “This is not a project for electronic beginners.” Indeed the 990 opamp is relatively difficult to DIY and is prone to oscillation if layout and grounding conditions aren’t just right. As an alternative, Jensen’s app note #82 details a similar circuit using inexpensive IC opamps, which can be viewed here: AS082 app. note.