AudiophonicsTM is the name I use for my audio designs which I originally developed between 1992 and 1996, and continue to work on some thirty years later.

I was prompted to design the 8" Sphere Speakers as I was unhappy with the sound quality of conventional square box speakers. There were also visual issues of a domestic nature to consider.

The Sphere Speakers were demonstrated at the 1993 Hi-Fi show at Heathrow, along with my Marble and Granite Shelving System.

The Sphere Speakers also featured in several Hi-Fi and other Lifestyle magazines including GQ and House & Garden (see the Reviews Page).

Following on from the Sphere Speakers I designed a separate Bass Speaker to extend the low end response. I considered several options and in the end settled on a sealed box design with two drivers mounted face to face. I was particularly keen to be able to reproduce classical organ music (Bach for example) which can play havoc with ported designs.

The Sphere Speakers however were so accurate with their light and fast aluminium cones ("The only enclosed speakers that sound as transparent as electrostatics." from one knowledgeable listener) that deficiencies in the audio quality, in particular the power amplifier, became apparent.  So I went back to first principles and after much contemplation the principle of the Zeus Audio Amplifier was born.

Original Zeus Amplifier Schematic - 1994 (updated 2004).

It took me the best part of two years to get from "I wonder if..." to "It works - and I understand why!". Along the way I had some interesting times trying to unravel the mysteries of transformer design.

Once I had the amplifier part of the audio chain sorted out my attention then came on the source reproduction side of things, as now deficiencies in that quarter were now apparent!

So in 1996 I built my own CD player from a hacked SCSI CD-ROM drive that had front panel controls for track selection as well as the standard play/stop button.


2004 - I restarted my audio work and over the subsequent months designed the upgrade Zeus75 power amplifier. Investment in a Hi-End sound card and measurement software gave me new tools for measurement and optimisation that I could only dream about a decade previously.

2005 - I extended the Zeus philosophy to a pre-amp / line driver and prototyped both mosfet and tube single ended versions using the same input and output transformers in both cases.

2006 - I started development of a RIAA pre-amp front end and a tone arm.

2007 - A the beginning of the year I built my end to end Zeus system which is used for daily listening (as opposed to "bits on the bench" for testing). This represents the minimalist system which I can build to order.

Please note however that being based in the UK I have to pay European prices for materials and since I am building one offs I don't get any savings in materials costs i.e. I pay just the same as you do when buying transformers from Sowter or Lundahl, or components from RS and Farnell. So if you would like me to build you a Zeus system, it will be suitably and reassuringly expensive.

2008 - I prototyped a number of internal DAC upgrades for my Oppo DV-980H optical media player. I also started full-time employment as a technician in the Department of Physics at Imperial College London.


2022 - Finally get everyting together and now our 5.1 system is entirly Zeus based. The Left and Right rear channels use the Zeus-35 amps I built back in 1995.


2023 - This year so far has been experimenting with singel-ended output configurations. I am still working for Physics at ICL.


See the discussion over at the DIYaudio Forum...

Zero Feedback Impedance Amplifiers


Email: susan@audiophonics.com

All design and other information, drawings and images on this website are
Copyright 1992-2023 Susan Parker MAES 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.