Among analog electronic devices, amplifiers are the most common. In everyday life, one most often has to deal with amplifiers of audio (low) frequency. In short, they are called UZCH or ULF.
Choosing a scheme
If you have never had to assemble an amplifier yourself, then it is best to start with a circuit on radio tubes. Single-stroke tube ultrasonic frequency converter is easy to set up. Its power is sufficient for reproducing sound in a living room, it can be used as an amplifier for an electric guitar or connected to a computer as a speaker. If lamps with a high steepness of the characteristic are used in the design, then the sensitivity of a single-tube amplifier will be enough for direct connection to the output of a computer sound card. The amplifier uses an output transformer to match the speakers.
Details
In this amplifier, you can use an octal radio tube 6P9 or its finger analogue - 6P15P. These lamps are found in older televisions and can also be purchased from the radio market.
The Tr transformer is suitable for the TVZ-1-9 brand, but you can use any single-ended output from a tube TV or radio. It's very good if you can get hold of a transformer with a speaker used with it. You can pick up the speaker with a power of at least 2W, resistance from 3 to 8 Ohm. You can use multiple speakers connected in parallel or in series.
Capacitor C2 is an electrolytic capacitor, its body is connected to the amplifier chassis. Capacitor C1 - any capacitor designed for a voltage of at least 350 V.
The variable resistor R1 is also taken from a tube TV, it is a volume control. Resistor R2 is of the MLT-2 brand, but another one, designed for a power of at least 1.5W, can be used.
The power supply can be used ready-made, for example, from a lamp radio receiver. The main thing is that it gives a constant voltage of 210-250V to power the anode circuit, and an alternating voltage of 6, 3V for heating the radio tube. In one of the variants of this design, the power supply unit of the Yunost electric player was successfully used without alteration.
Construction and installation
The amplifier is mounted on a U-shaped metal chassis, which can be used as a cover from an end-of-life CD drive. Variable resistor and input connector are located in the chassis tray. If the amplifier with speakers and a power supply is made in the form of a monoblock, then be sure to make sure that the direction of the transformer coils is mutually perpendicular.
The entire installation is hinged. Insert the lamp into the panel only after finishing installation and soldering, this will protect it from damage. The speakers are mounted separately on an acoustic board made of 5mm plywood. The whole structure is placed in a plywood case covered with leatherette. You can also place the speakers in a separate speaker box. You can also mount the power supply separately and connect it to two similar amplifiers, making a stereo system.
Adjustment
If a powerful hum is heard from the speakers when you turn on the amplifier, swap the input windings of the transformer Tr. With proper installation and serviceable parts, the sound through the speakers should be clear, with no noticeable background. This completes the setup of the amplifier. When using the amplifier as a guitar combo, connect it via a preamp or effects pedal.
