Deliang DE1102 digital tuning radio function simplified and sound quality improvement machine ----- Sound Quality Improvement

Keywords: radio sound quality motor The sound quality level of DE1102 is flat in the same level, analyzing its low channel design mainly with the following issues. First, the entire low-ample passage is divided into a predetermid, and two partial circuits are served by U3 (LM4811) and U7 (V733), respectively. The U3 also has an electronic volume control function, but U7 has a high gain, and it is necessary to connect with the U3 to meet the speaker's playback volume. The electronic volume control range of the U3 is not wide enough, the designer has additionally added an electron attenuation circuit composed of RIIO, Q24, RIII and RL20, Q26, RL21 in order to broaden the control range). Since the resistance of RIIO and RL20 is large, there are too many attenuation of the audio signal, which makes the incomplete gain "snow", the volume of the machine is not enough, so the designer has added a low amplification of the three-pointed QL3, QL6 and the like. The front stage voltage is enlarged to make U3 a second prefix. Such a design is actually not ideal, and the audio signal is amplified before the decay is unreasonable from principle) and the three-level amplified series will inevitably lead to an increase in nonlinear distortion of the entire channel, and is harmful to the sound quality. Second, the original designer adds a series of circuits such as switched tone adjustment, Bass overweight bass, and stainless control, so that the circuit output from the U2 output to the prefix low U3 input is too much, used in the channel The coupling capacitance capacity is not large, and the result is limited to the frequency band of the audio signal, resulting in frequency distortion, which inevitably affects the sound quality. Third, the quality of the speaker unit of the machine is generally, the frequency is not wide enough, due to the size limit, naturally not too good: but in the treble, there is too fast, the play is only the intermediate frequency has a good response. This has great effect on the sound quality of the whole machine. The machine has invested many cardioptrips and costs in the design of the SSB (single sideband) reception function, but the reception effect of this function is not ideal. The author has always opposed the installation of the SSB reception function on a small radio, because the signal is received, often requires an external long antenna, and is limited by the receiving environment, and is very unsuitable for mobile use. Small radio. Pursue this function, some unreal, waste funds and technology, make the radio structure complicate, the actual rod antenna may only receive some noise and whistling signals, there is no significance. The author has removed this part of the circuit and leaves the space and uses it. The design of the high-frequency intermediate frequency circuit of the machine is still relatively excellent, it is best to do it in amateur conditions, otherwise it may cause the frequency to chaos.