Valve/Tube Low Frequency amplifier 30W

The amplifier in this design is rated at 30 Watts and is intended for use with a microphone. It is compatible with a crystal microphone and can be utilized for speeches, lectures, as a transmitter modulator, and in applications where a common frequency amplifier is beneficial. The frequency range it amplifies begins at 50 Hz and extends to 10 kHz. At these frequencies, the gain decreases by 3 dB. The distortion level of the amplifier is approximately 8%. The output stage employs two 6L6 tubes in a push-pull configuration. Additionally, two ECC83 tubes are used for pre-amplification. The volume control is managed by potentiometer R1. The output transformer T1 has an impedance of 10 kΩ, with the primary winding rated for 100 mA, and it must feature a core suitable for 30W power transfer. If the secondary of transformer T1 is connected to a loudspeaker, it should have an impedance of 8 Ω. When used as a modulator, the impedance requirement is 10 kΩ. The power supply includes a primary voltage of 220V and a secondary output of 2x 350V at 150 mA, 6.3V at 3A, and 5V at 2A. The smoothing filter choke is rated at 10H for 150 mA.

The 30 Watt amplifier circuit is designed to provide high-quality audio amplification, particularly suitable for applications that require clear sound reproduction from a microphone source. The use of a crystal microphone allows for efficient sound capture, making it ideal for environments such as auditoriums or public speaking venues. The frequency response of 50 Hz to 10 kHz ensures that the amplifier can effectively handle the audio spectrum relevant for speech and general audio applications.

The push-pull configuration of the 6L6 output tubes enhances the amplifier's performance by minimizing distortion and improving efficiency. The ECC83 pre-amplification stage further optimizes the input signal, allowing for greater control over the audio output. The incorporation of a potentiometer (R1) for volume adjustment provides user-friendly control over the output level, facilitating easy operation during live events.

Transformer T1 is critical in the design, serving to match the impedance of the amplifier to that of the connected load, whether it be a loudspeaker or a modulator. The specifications of T1 ensure that it can handle the required power levels without overheating or saturating, which is essential for maintaining audio fidelity. The power supply's dual secondary outputs cater to the needs of the amplifier circuitry, providing necessary voltages for both high-voltage operation and filament heating of the tubes.

The inclusion of a smoothing filter choke rated at 10H for 150 mA is fundamental for reducing ripple in the power supply, thereby enhancing the stability and performance of the amplifier. This design ensures that the amplifier operates efficiently, delivering clear and powerful audio output suitable for various applications.The amplifier of this design is 30 Watt and is suitable for microphone-inducing. It accepts a crystalline microphone and can be used for speeches, lectures, as a transmitter modulator and generally where it can be useful as a common frequency amplifier. The frequency range it amplifies starts at 50 C / S and reaches 10 KC / S. At these frequencies the boost falls by 3DB. The deformation of the amplifier is approximately 8%. The output consists of two 6L6 in Push-Pull configuration.

The two ECC83 lamps make the pre-enhancement. The potentiometer R1 is used to adjust the volume of the voice. Output transformer T1 has an impedance impedance of 10KΩ. The primary wire is for 100mA and this transformer must have a core for 30W power transfer. If its secondary transformer T1 is to be connected to a loudspeaker, it should have an impedance of 8Ω. If used as a modulator then it must have a 10KΩ impedance. The power adapter has a primary 220V and a secondary 2X 350V for 150mA, 6.3V for 3A and 5V for 2A. The smoothing filter choke is 10H for 150mA.