Zeus Preamplifier - Mosfet
Zeus Stereo Mosfet Preamplifier & Power Supply - Concept CAD Sketch
for new Prototype.
This concept CAD sketch is for my new version
preamp prototype. It is designed to incorporate my 24 way reed
switch attenuator and newly designed radial reed switch XLR
input selector. The latter stereo pair are mounted side by side
and connected by toothed timing belts, the overall assembly
being accommodated in the rear section of the preamp.
24 way reed switch attenuator PCB (with operating magnet
The 24 way reed attenuator switch is built up in sections and
allows for either discreet wiring to a TVC or on the reverse has surface mount
resistor sites for conventional or ladder attenuators. Each section has a radial
arm mounted on the central shaft which contains a magnet that operates the reed
Radial reed switch XLR input selector - PCB drawing.
An 8 way reed input selector switch plus tape loop using the
same switching principle as the attenuator.
All three pins on the XLR connectors are switched, with an
individual option to ground or leave open circuit for Pin 1. This arrangement
reduces to an absolute minimum the internal signal paths of any source that is
not specifically selected.
The individual XLR reed groups are arranged to ensure that the
XLR Pin 1 ground is always made before the audio path is made and is always held
until after the audio path is broken.
In addition as the magnet arm is moved from channel to channel
it passes over a mute reed.
Zeus Stereo Mosfet Preamplifier Prototype.
The prototype front panel layout is going to be reorganised
with the volume control in the centre and the input selector to one side. A
hard mute/standby switch will be on the other side to balance the visual
Each channel has it's own voltage regulator (I used
to 27 volts) and has a diode on the input to guard against reverse
(Not shown in photograph) As the preamp is single
ended I use a reed relay in the output circuit of each channel to open
circuit the transformer secondary to prevent power cycling transient to
the power amps.