Zeus Power Amplifiers

A Zero Feedback Power Amplifier

"The perfect amplifier is wire with gain"

General Amplifier Schematic

Amplifier Highlights

  • Zero feedback.
  • Balanced and isolated input and outputs.
  • Output configurable to drive any impedance load, from electrostatics to sub-ohm parallel linear array loudspeakers
  • Good EMI/RFI performance.
  • Low voltage operation ( sub 60 volts ), no potentially lethal HT.
  • Only two power semiconductors required for Push Pull version.
  • Minimum components, little opportunity for noise generation (150 dB signal to noise ratio).
  • No capacitors in the audio signal path.
  • "Direct" signal connection from input to output.

Zeus System - Pre + Power

Full end to end configuration with TX-102 TVC input.


Class A (AB) monoblock power amplifier with separate PSU.

Zeus 75 Amplifier and Power Supply Concept CAD Image

Zeus 75 Distortion versus Power Output.

Use with 4 ohm impedance speakers with 2:1 step down output is not normally recommended but this graph is to demonstrate the amplifier operation where distortion level plateaus at 1% (unlike conventional amplifiers where it would continue to rise).

Power at maximum output is over 100 watts.

Note: Full Class A or Class AB operation depends on output transformer configuration, mosfet bias level and load being driven.


Building a Zeus 75 - Information on Construction

Input Transformer Specification

Output Transformer Specification - 75W

MOSFET Matching with L200 Current Source

FFT Test Result with 2SK1529 Audio FETs

Zeus Pre-amp / Line Drivers

SE and PP pre-amplifier variations.


Zeus SE MOSFET Line Driver - info & FFTs

TX-102 variable attenuator mosfet preamp line stage.

Zeus 6C33C Triode PP Line Driver - info and FFTs


Zeus PP MOSFET Line Driver - info & variations including SE & toroid output transformer.

Zeus 35 Monoblock Power Amplifier

My original prototype power amplifier.

Original Zeus 35 Amplifier Internal View - One of a Pair.

Original IRFP150 35 W Amplifier built in 1995

With FFT and THD+N test results

Additional Experimental Information

These pages show examples of what can be done with the Zeus topology.

Single Ended Version


Toroid Transformer Version

3rd March 05 (updated schematic plus added notes).

2 Stage Amplifier - Variations

Schematic Diagrams - misc

Includes temperature tracking Vbias schematic.

Output Transformer Tri-Filar Winding Illustration.

This image shows the basic principle of how the
multi-filar transformers are constructed.

Email: susan@audiophonics.com

All design and other information, drawings and images on this website are
Copyright 1992-2010 Susan Parker MIET (unless otherwise credited).

These designs and other information may be used to construct systems specifically for personal NON commercial use only.

N.B. Personal liability disclaimer applies - see T&C.