Abstract: The present invention relates to electronic percussion musical instrument system, and particularly to an electronic drum, which comprises one or more electronic control units to generate sounds. The system has an upper surface, which receives the percussion and is covered by a rubber layer useful for giving a realistic rebound to the musician, a lower surface and an electromagnetic sensor operating according to the Faraday-Neumann-Lentz physics law, which has a magnet placed in adherence to the upper surface and a bobbin applied to the lower surface, and a shock absorber spacer arranged between the two surfaces to allow the two components of the electromagnetic sensor to remain in reciprocal suspension.

Abstract: A valve power amplifier stage for an audio amplifier, which amplifier stage has at least one thermionic valve and a polarization circuit for polarizing the anode, the cathode and the control grid of the thermionic valve so as to determine the maximum output power. The polarization circuit comprises an adjusting module for adjusting the feed voltage of the anode and the polarization voltage of the control grid so as to adjust the maximum output power of the thermionic valve, and a potentiometer coupled with the adjusting module for allowing a user to control the adjusting means so as to select the desired maximum output power from a plurality of predetermined output power values.

Abstract: A valve power amplifier stage for an audio amplifier, which amplifier stage has at least one thermionic valve and a polarization circuit for polarizing the anode, the cathode and the control grid of the thermionic valve so as to determine the maximum output power. The polarization circuit comprises an adjusting module for adjusting the feed voltage of the anode and the polarization voltage of the control grid so as to adjust the maximum output power of the thermionic valve, and a potentiometer coupled with the adjusting module for allowing a user to control the adjusting means so as to select the desired maximum output power from a plurality of predetermined output power values.