Class AB1; Power Output, 15 Watts

This circuit was found in the RCA Receiving tube Manual, 1970 edition.

**Circuit Description **

This high-fidelity audio power amplifier can deliver 15 watts of ms output power with less than 0.4 per cent total harmonic distortion and less than 1.5 per cent intermodulation distortion.

The frequency response of the amplifier is flat within 10.5 dB from 20 Hz to 60 kHz, and the sensitivity is such that the rated output of 15 watts is obtained for an input of 1.2 volts ms.

The total hum and noise, with the input shorted, is 84 dB below 15 watts.

The circuit operates from a 117-volt ac power line.

The transformer-coupled ac input power is converted to dc operating.

C1 - 40 µF, electrolytic. 450 V.

C2, C4, C5 - 0.25 µF, paper. 400 V.

C3 -- 3.3 pF, ceramic or mica. 600 V

C6 -150 pF", ceramic or mica 400 V.

C7. C8 - :0.05 µF. paper 400 V.

C9 - :0.02 µF. paper 600 V.

C10 – 100 µF. electrolytic,

C11- 80 µF electrolytic, 450 C

C12 – 40 µF . electrolytic.

F1=Fuse. 3 ampere:

L1=Choke. 3 H, 160 mA. Dc resistance 75 ohm: or less,

R1=Volume control. potentiometer. 1 megohm

R2=10000 Ω. 0.6 watt

R3=0.82 megohm. 0.5 watt

R4 =820 Ω, 0.5 wntt

R5=0.22 megohm. 0.5 watt

R6, R7=15000 ohm :5 per cent. 2 watts

R8=3900 Ω. 2 watts

R9, R10 = 0.1 megohm, 0.5 watt

R11. R12-1000 Ω, 0.5 watt

R13, R14 -1100 Ω. 0.5 watt

R15 -8200 Ω. 0.5 watt

R16=15000 Ω, 1 watt

R17 -68000 Ω. 0.5 watt

R18 - 4700 Ω. 2 watts

R19 -0.27 megohm, 1 watt

R20 =47000 Ω, 0.5 watt

R21=Hum balance adjustment potentiometer, 100 Ω, 0.5 wntt

SR1=Selenium rectifier.,20 mA, 135 volts rms

T1=output transformer. (having 8-ohm up for feed-back connection) for matching impedance of voice coil to 6600-ohm plate-to-plate, tube loud; 50 watts: frequency response. 10 to 50000 Hz:

T2=Power transformer. 360-0-360 volts rms. 120 mA; 6.3 V., 3.5 A; 5 V., 3 A: