HI-FI Amplifier with Tone Control 01

In order to improve the adaptability to various sound sources, the high-quality and cheap Gaul (=97-5) double three-pole arm 6NZ is specially selected to form the line
input amplifier (half of the VEIL of 6N2 is used for the left channel , and the other half is VEIR For the right channel ) R2 is
the DC bias resistor of the input stage. When the screen current I, o flows through R2, a DC voltage of about 1.5V is generated. The gate drain resistor Ri is added to
the gate of VEIL to form a negative gate voltage of the line amplifier . At this time, VEIL is working in Class A status and has good linearity.
The second function of RZ is to produce an appropriate amount of AC feedback to the audio source signal, further reducing distortion and further improving stability; R2