We see some of its technical advantages and limitations. The interior of Model 2203 In 1962, the unique equipment that used transistors was 2203 Model and Model 2211 (Indicating of sonorous limit). All the others had valves. The transistors that existed at that time were of germanium and they did not have the high gain generally, under noise and low leakage current that was required. Speaking candidly Estee Lauder told us the story. For that reason it was necessary to classify the transistors by classes and to use best in the places more the critics (the same took control of the rheostats, who could only be obtained with a tolerance of 20% and they were become ordained in classes of 2%). The preamplifier of the microphone also was something special. For this component, the transistors totally were discarded and was necessary to use a valve. A local oscillator fed the cathode on the small valve, warmed up directly, through a transformer, and the valve could be used then like prolongation of the cathode.
The valve was suspended in a device of wharves to avoid an excess of microacoustic effects. Acoustics It was not easy to make measurements acoustic of the microphone and the box. Brel & Kjr did not have camera anechoic, nor either the DTH (later well-known like DTU, Technical University of Denmark). The measurements were done using a model of the instrument with half of size, located in an asymmetric box, of about two meters in length, that absorbed sound. This configuration was not too precise and, in fact, later measurements demonstrated that the acoustic behavior was not the awaited one. The microphone mounted in the vertex of the cone of the housing and the influence of about 2 housing was of dB, instead of 1 dB that was expected. This was corrected a posteriori inserting " neck of cisne" between the microphone and the housing.