Amplifier for driving electrostatic loudspeakers

An amplifier for driving a capacitive load and adapted to receive a signal in the audio frequency range from an associated preamplifier source, the amplifier comprising:

• at least one power output tube arrangement including a driving tube with mean connected to drive a driven tube;
• and an output section connected to cooperate with said power output tube arrangement, said output section including:
• (a) a feedback network;
• (b) a difference amplifier, said difference amplifier including a pair of complementary drive transistors, the first of said pair of drive transistors having a collector output connected to an input of said driving tube of said power output tube arrangement, the second of said pair of drive transistors having a base input connected to an output of said driven tube of said power output tube arrangement through said feedback network, and,
• wherein said feedback network includes a first resistor connected in series between said base of second transistor and said output tube arrangement, a second resistor connected between said base of said second transistor and ground to form a bleeder network with said first resistor, a third resistor connected in parallel with a capacitor disposed between the emitters of said first and second transistors to adjust gain and phase for stability, and a guard device connected to the base of said second transistor to protect said second transistor from high voltage spikes, and a compensation capacitor connected between the output of said output tube arrangement and the base of second transistor to achieve flat frequency response at said audio frequency range in said feedback network, and
• the phase of said first transistor is connected to receive said audio range signals, and
• whereby said power output tube arrangement in cooperation with said transistorized difference amplifier provide low distortion, positive self-certering and high order stability power amplification of said audio range signals.