Polisois Ari Ari Polisois was attracted to electronics at the age of 10, after meeting a friend who showed him some components and a crystal radio he had assembled.He asked his parents to buy his first valve (an 117Z3) and started to make experiments. In spite of a couple of electric shocks, he managed to survive, but the valve did not last long.He next built a walkie-talkie, a Mullard stereo amplifier and a broadcasting station to send music to a friend living in the next block. He studied electronics at the Ecole Centrale de T.S.F. with the well known master Lucien Chrétien, the inventor of the anti-fading system, eventually graduating in Economics and Trade, at the Milan University of the Sacred Heart. Once retired, he build a couple of classic amplifiers, which were published in Glass Audio. Soon he got involved in investigating new approaches aimed at improving sound reproduction. He concentrated on Single Ended amplifiers and their audio transformers and, as a result, was eventually granted three patents for the Direct Coupling Modulated Bias circuit and a novel output transformer design (self compensated with flux escape) for single ended circuits. With Giovanni Mariani of Graaf Amplifiers he obtained a fourth patent covering the Split Core – Stereo Common Circuit transformer that achieves a substantial reduction in cost, bulk and weight, with respect to a pair of standard gapped output transformers and, at the same time, improving the bass of the single ended amplifiers. Ari Polisois now writes articles on valve amplifiers and output transformers for several magazines (AudioXpress former Glass Audio, Elektor Holland, Elektor Germany, Costruire HI-FI Italy and Linear Audio) as well as doing some advanced research in the field.
Ari has been publishing his DC-coupled, Modulating Bias design as the Simplex amplifier. In this article, he combines this technology with the Split Core Stereo Common Circuit transformer design...