Since CD players have been popular for many years, many families already have a set of stereo Hi-Fi combo speakers. On this basis, upgrading to a home theater is quite simple. As long as the decoder is configured, you can receive the Hi-Fi upgrade and increase the AV function. The best of both worlds. Recently, Octopus launched a DV-315AV decoder, which is a product that upgrades Hi-Fi combo to a home theater. It has directional logic decoding function, with AC-3 (5.1 channel) input port, built-in three-channel power amplifier, with perfect karaoke function. This article introduces the circuit and function of the DV-315AV decoder for the reader's reference.
The main components of the DV-315AV decoder circuit are shown in Figure 1. The core of the decoder is M69032 professional directional logic decoding IC of Mitsubishi Corporation of Japan. M69032 is currently a logic decoding IC with high utilization rate in AV power amplifiers, and ideal performance indicators and AV effects. It can demodulate the dual channels with Dolby surround information into the L, R main channels, and the middle. The placement of channel C, surround channel S and additional subwoofer and other signals can produce synchronized sound space movement effects with the change of the film image, making people immersive and enjoying extraordinary AV fun. In addition to the common standard (Normal), phantom (Phantom), and wide (Wide) surround modes, the decoder also adds a center three-channel stereo mode. This mode is ideal for enjoying human voice. This is because with the center channel, the sound field distribution is more uniform and the liveness of the singing is more realistic. In order to meet the requirements of AC-3 home theater, DV-315 is equipped with AC-3 (5.1) input port, which can directly bring a 5.1-channel output DVD player. It can be seen from the circuit shown that there are three power amplifiers with pre-amplification in the machine, which are used for center, surround and left and right power amplification. Preamplification is done with an op amp, and proper gain can be easily matched with sources with different output sensitivities. The power amplifier circuit is the LM3886 power amplifier chip produced by National Semiconductor Corporation. The LM3886 has low distortion, wide frequency response, fast response, and an output power of 68W. It can fully meet the high standard of AC-3 and can restore the shocking AV site effect under home conditions.
DV-315 is equipped with a digital reverb karaoke function with outstanding effects. The relevant circuit is shown in Figure 2. The center of the reverberation circuit is the M65831 special chip of Mitsubishi Corporation of Japan. M65831 can be said to be the evergreen tree of karaoke circuit. Many middle and high-end equipments have their shadows, and the effect is beyond doubt. The microphone signal is composed of a TL082 integrated circuit divided into two channels to form an inverting amplifier as an input amplification stage, followed by an attenuation negative feedback hybrid microphone high and low tone control circuit composed of TL082. The microphone amplifier circuit and its volume control circuit are completely independent, which can reduce the modulation distortion, and the singer's voice is clearer and more natural. W3 is the ECHO reverberation depth adjustment, K1 switch can achieve two delay time adjustment. The signal processed by M65831 digital delay and the microphone direct signal are mixed by IC4, and then sent to the pre-amplifier circuit of the music channel to be mixed with the accompaniment music. The karaoke signal has a cut-off switch (KARAOKESW), which can completely turn off the signal of the karaoke circuit when listening to music, eliminating the adverse effects of the digital reverberation circuit on the original sound of the music. It is worth mentioning that the high and low tone control circuits of the microphone are designed very well, and the amount of control is also appropriate. During the singing, the tone can be adjusted appropriately according to the use environment and the characteristics of the microphone, so as to beautify the human voice without Affect the purpose of accompaniment music.
figure 2 In the DV-315AV decoder, in order to ensure the fidelity of music, all the switches are controlled by contact switches or relays to avoid the damage to the sound quality caused by the use of some low-end analog switches. The volume is controlled by a high-quality six-potentiometer produced by Japan ALPS, which meets the requirements of AC-3, and can achieve synchronous adjustment of 5.1 channels. The total volume, center and surround volume, and sound source switch are all controlled by the long axis to reduce the signal channel and avoid signal loss and distortion. The decoder board uses double-panel wiring, the components are well arranged, and the process is very delicate, which is extremely rare on affordable AV equipment.
The appearance of the DV-315AV decoder is very simple. The panel is mainly champagne-colored, and it is equipped with a golden knob. The function knob of the karaoke part is matched with a black substrate. Due to the contrast of the colors, the composition of the panel is rich. Colorful, with a strong sense of the times. The decoding control of DV-315 is handled by a single CPU, and the cumbersome control function becomes quite concise after being processed by the CPU program. Four buttons and a row of indicator lights can realize man-machine dialogue. The function is very clear and extremely convenient.
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