Balanced supply voltages of 60 volts do in fact guarantee lots of "headroom," or high overload stability, as well as nearly unrestricted dynamics, but apart from power amplifiers as seen within the hi-fi world, these voltage concepts are notably rare in other audio applications, due to cost considerations. They usually only make sense if the amplifier sections are built up with discrete components that are able to cope with these voltages. In the studio equipment sector, SPL has successfully been using this technology for years, as the test reports on the Phonitor 2 and the Director from their Pro-Fi line for home use show. Regarding the voltage supply of the Strumento n°1, I should add that the aforementioned 40 electrolytic capacitors are located under a special plate to eliminate electromagnetic interference, as well as to limit mechanical vibrations, while "ultrafast" diodes take over the rectification process.

In order to illustrate the circuit topology of the preamp, I follow the signal from the input to the output sections. Let's start at one of the two RCA or one of the five XLR inputs. Right behind the input selection are relays, which also disconnect the ground connection of the non-active XLR inputs from the circuitry; two buffer amps take care of the inverted and the non-inverted part of the now purely balanced signal. The non-inverted signal for the tape recording output is then branched off and fed to the RCA output sockets after further buffering. Behind the two buffer amplifiers of each channel, the Audia Flight features not less than two volume controls: a discrete one with very low-noise metal-film resistors and relays, and one using the PGA2310 IC. The control electronics of the preamplifier decides which of the two has to be active in the signal path. If the volume setting is on a constant level, relays and resistors define the level. If the volume level changes, the PGA2310 immediately takes over, since it runs totally silent during the control process—unlike the discretely operating controllers. After the relays and resistors having adjusted the required volume level, the control electronics switch the discrete ones back into the signal path.

The company's director Massimiliano Marzi notes in his e-mail that the PGA2310 works so well that it is used in many competitive products for the level control itself. However, their proprietary design with relays and resistors gets a good bit closer to the ideal conception of an entirely loss-free volume control with a constant-impedance behavior. And in his eyes that more than justifies the additional expense. Only if the impedance throughout the volume attenuation process does not change will the edge steepness and the frequency response remain constant. Audia Flight's "constant impedance attenuator" leaves other solutions far behind, and allows for the extremely extended frequency response from 3Hz to 1mHz with a deviation of a maximum of 3dB and a slew rate of more than 250 volts per microsecond in the entire level range from -90 to +10dB. The circuit's control range comprises 127dB in constant steps of 0.5dB, whereby the level adjustment runs fully silent without creating any clicking noise in the loudspeakers.