The 100W bass amplifier is designed for installation in a speaker cabinet. It consists of three sections located on separate printed circuit boards: a subwoofer filter section and a power amplifier section with protection.
The first section is the subwoofer filter. At the input, the signal from the right and left channels is collected, connected to the volume control and then to a separate amplifier with modified frequency characteristics. Next comes a third-order active subsonic filter connected to a second-order adjustable low-pass filter, which can be bypassed with a switch if necessary.
The final block is an output amplifier with a 180° phase shift. The second section is an output amplifier. It consists of an input amplifier, a frequency response stage with quiescent current control, an excitation stage, and an output stage with short-circuit protection at the output. Adjustable from 30Hz to 300Hz
Subwoofer filter parameters
Input impedance: 10kΩ
Nominal input voltage: 0.775V
Nominal output voltage: 1.55V
Subsonic filter cutoff frequency: 18Hz, slope: 18 dB/octave
Low-pass adjustable from 50Hz to 310Hz, slope: 12dB/octave bridging
180° phase rotation option
Gain control from -29 dB to 10 dB
Output impedance: 100 Ω
Protected power amplifier parameters
Nominal input sensitivity: 1.5V for 100 W/4Ω
Input impedance: 10kΩ
Frequency range: 5Hz to 150kHz, tolerance band: -3dB
Amplifier power supply: symmetrical ±35VDC
Speaker connection delay time: 2s
DC protection sensitivity: 2V
Overcurrent protection sensitivity: 3A
The third part is speaker protection with a delay connection during turn-on and protection against direct voltage at the amplifier output. The subwoofer speaker is connected to the output of the speaker protection.
A subwoofer is a bass unit used to support speakers with the lowest frequencies in the audio spectrum. It is often used to support sound effects in movies or stereo satellites with frequencies below 100 Hz.
Subwoofers have a frequency range between 20 Hz and 200 Hz. A subwoofer speaker is generally large in diameter to reproduce the lowest frequencies. It is usually the most powerful speaker in the entire system. It is usually housed in a bass reflex-type enclosure characterized by one or more holes tuned to the enclosure’s resonant frequency. This tuned enclosure then reproduces lower frequencies and has a more balanced frequency response.
Frequency Filter: A frequency filter is a circuit whose function is to pass or, conversely, suppress certain frequencies. They can be divided according to several criteria. According to the transmitted band, they are divided into high pass, low pass, band pass and band stop.
