Hi-end power amplifier circuit

This article will introduce the "MAS" 2×50w power amplifier. Its circuit principle is shown in Figure 2-34. This power amplifier
adopts the form of fully symmetrical and fully complementary DC amplification. The barrier circuit consists of a dual differential input stage, a voltage amplification stage, a push stage, a parallel
push-pull converter output stage, a bias circuit and a DC servo circuit.
    VTi - VT4 form a fully symmetrical dual differential input circuit. This differential circuit does not use the transistor constant current source t commonly used in differential circuits.
Instead, it uses high-speed electronic filters composed of VT14, VTi5, VT16.v, rl7, etc. to provide
stable positive and negative symmetrical power supplies , which greatly The ripple coefficient of the power supply is reduced and a high-quality purified power supply is achieved .
    VT5 and VT6 form a complementary push-pull voltage amplifier stage, and C3 and C4 are compensation capacitors to enable the circuit to self-excite.
    vrs and VTg form the output push stage, and adopt a midpoint floating connection method to force it to be in a Class A state
to improve crossover distortion. Vr7, VI U, VI V and RP form a bias circuit.
    VTio ~ VT13 form a parallel push-pull power amplifier output stage, which uses a pair of fT up to 60MHz, which is unanimously
recognized by the audio industry, has excellent linearity without "transistor taste", and has a larger dynamic range, less distortion and
higher power than MOSFET. "H beautiful sound" to the tube. In order to prevent self-excitation, the base of each tube is connected in series with an anti-vibration resistor.
    From the analysis of the principle of DC power amplifier, it is known that in the DC power amplifier, the feedback capacitor is cancelled, which reduces the differential input
level input resistance. In order to make up for this shortcoming, many circuits adopt differential input circuits. However, double differential circuits have very strict requirements on the matching of
tubes , so it is difficult to meet the requirements in practical applications, and the balance of the circuit is not ideal. . This circuit
uses a "DC servo circuit". Due to its extremely high adjustment sensitivity, the balance of the circuit achieves a very ideal effect.