Description
Lombardi Amplificazioni boasts decades of experience in sound amplification using Thermoionic Valves.
The continuing market demand for high quality all tube preamps are the basis of this project.
The main difficulty was that of interfacing the tube preamplifier stage with a low output impedance to an external amplifier stage both with tubes and above all with transistors which has an equally low input impedance.
This configuration results in signal loss and radically changes the sound response in a negative way.
To overcome this problem, a tube impedance matching stage has been developed which acts as an impedance separator and adapter, which keeps the sound characteristics unchanged with any type of amplifier connected.
To obtain a high output impedance from the adapter stage, it was decided to use the two triodes contained in a valve type ECC82 in CASCODE configuration where the output driving is obtained by controlling the anode voltage of the second triode through the cathode of the first triode by phase shifting piloting the grids.
In this way the output impedance is high and the signal is doubled while maintaining the sound characteristics unchanged.
The signal thus obtained has the optimal characteristics to drive an input stage of any type.
The frequency response given by an all tube preamplifier is very high and rich in harmonics which makes it ideal for driving new generation amplifiers (class DGH etc.) which have reduced frequency responses due to their configuration, restoring a natural warmth to the reproduced sound. .