MARCONI is our new top of the line preamplifier. We have chosen this name as an hommage and a reflection towards the great inventor.

In the never ending search for tonal improvement in amplifiers, the development is often limited in the loss that is generated by components and other interferences. The symmetrical technique has been introduced to prevent these interferences or at least to minimize them. Therefore all the amplifier stages are doubled to carry the signal in both forms, the original one and an inverted one, which is 180° phase shifted. In the power amplifiers these two signals are backed together to form one signal again. This cancels all the tonal characteristics of the components and other interferences to zero, but the music is able to pass unconterminated.

We use this technique in our MARCONI preamplifier to further reduce all existing influences in an endeavour to keep the tonal influence of the components as small as possible. The phase inverters that are responsible for the symmetrical signals work with tubes. Tubes respond to the input signal without a noticeable time delay. Allowing a free syncronical and symmetrical signal. The outputs are provided by four identical, low output resistance transistor amplifiers.

Our asymmetrical preamplifier CALVIN uses the same output stages and the technical details described there are also valid for the MARCONI preamp.

The preamplifier is equipped with six linear-inputs, 5 of them correspond to asymmetrical and one to symmetrical signals. As a special feature, the input levels of all the six inputs are individually adjustable, so the user can set the same level of loudness for every connected source. The outputs are both, symmetrical and asymmetrical, the phase can be switched between 0° and 180° via remote control. A record output completes the rear panel layout.

The power supply for the preamplifier is build into a separate casing. All components that emit heat have been placed in the preamplifier. It's large enclosure with heat sinks on both sides is much more capable to dissipate heat. The tubes are placed inside the heat sinks, enabling the heat to dissipate. So only the power transformer is left in the power supply casing. The power switch on the front panel of the preamplifier activates the secondary low voltage and the high voltage rails for the tubes via three relays.

A special feature of the preamplifier is its fully electronical control for level as well as for volume. An AD-converter interrogates the motorpot at the front panel and this information formed as a digital word is fed into the digital potentiometer-ICs to control the volume passively via a few hundred integrated resistors.

This technique allows to drive the four outputs with the same volume, there are no differences between the channels. The volume can be adjusted with a rotary knob on the front panel of the preamplifier or via remote control. A mark at the rotary knob allows the visualization of the volume setting level.