A Simple but Good Electrostatic Amp

This grew from a discussion started by ericj on the head-fi forum. The interest was in designing an inexpensive but good quality stat amp that could be an entry-level or better stat amp for diyers who are ready to make the leap from dynamics to electrostatics.

The first design, done on the fly on the thread, had a few flaws that prevented it from working. This turned out to be a good thing as it forced me to think harder about how to simplify the amp as much as possible. The eXStatA grew out of the ashes of the first design and the extreme simplification of the circuit.

Some of the original design goals as posted on the thread were:

  1. Use easily obtainable parts.
  2. No exotic transformers in the power supply.
  3. Accept balanced or single-ended inputs.
  4. Have multiple or adjustable bias voltages.
  5. Cost less than $300 before casework.
  6. Powerful enough to drive SR-Sigma in standard configuration.
  7. Tube or solid state or hybrid, whichever works.

The eXStatA amp seems to satisfy these requirements and comes in two versions: an all solid state version and a hybrid version.