LM4766 electronic two-way power amplifier and speaker production circuit diagram

Audiophiles with strong hands-on ability can make high-performance audio equipment by themselves. An example is given below.

First, the electronic two-way power amplifier. The pre-stage crossover is better than the power crossover, and the insertion loss is small, and the crossover point can be flexibly adjusted according to the performance of the speaker unit. However, the pros and cons of the prescaler circuit determine the effect of the electronic crossover amplifier. At present, domestic amateur production uses complex RC active circuits as the pre-stage frequency division. The steepness of the frequency division curve is selected above 12dB/oct or 24dB/oct. Thus, due to the large number of components, the frequency division accuracy is affected. The debugging is complicated, and the amateur production is not convenient. In fact, sometimes only one RC passive crossover network can be used, so that the crossover point is more accurate and has better amplitude characteristics and phase characteristics.
The electronic two-way power amplifier complete circuit consists of high, medium and low-frequency pre-stage processing and LM4766 × 2 power amplifier (see Figure 1 for the circuit).
LM4766 is a new product of American NS company. It is full of sound and can make up for the shortcomings of small and medium-sized speakers. It is known as IC amplifier with amp flavor. The main indicators of LM4766 are as follows: working voltage is ±10V～±30V, the limit value is ±35V, so the transformer secondary voltage is required to be between AC double 18V to double 22V. The continuous output power is (8Ω) 40W×2, the distortion is 0.009%, and the signal-to-noise ratio is 112dB. The internal has over-voltage, under-voltage and the company's patented technology - SPIKE peak protection in the safety zone, so there is basically no noise during the on/off, which provides convenience for the installation. The LM4766 has a two-channel internal structure, and the two-channel electronic crossover amplifier requires two ICs.
Note that the resistors are all selected from 0.25W five-color ring metal film resistors. The capacitors are preferred by CBB and MKT. The coupling capacitors are red WIMA and the filter capacitors are 10000μF. Ruby and black gold steel are preferred. The transformer is powered by a 300W ring cow. The ring has a dual 20V main winding and a dual 12V secondary winding. The dual 20V main winding is available for the LM4766×2 electronic two-way power amplifier board. The tone board has four potentiometers and a rectifying and filtering ±12V voltage regulator circuit. It can work with AC 12V. When the printed board is designed by itself, pay attention to the grounding direction to avoid introducing interference.
After the production is completed, you can check the following steps: 1. The secondary voltage of the transformer should be AC ​​20V, 12V, and the voltage after rectification and filtering should be ±28V, ±12V. 2. The LM4766's {2}, {15} pin voltage is +28V, the {4} pin is -28V, the {11} pin voltage is -5V, the other feet are 0, and the op amp OP275's {8}, {4} feet The voltage is ±12V, and the other feet are 0. After basically no error, you can access the speaker to listen.
Second, the production of speakers. A set of audio, the speaker is very important, the cost should account for 50% of the entire sound system, here is recommended a set of two-way bookshelf speakers, see Figure 2. The speaker is selected from the asset "Diandi" brand, the bass is YD165-8X (8Ω40W), the treble is soft ball top (8Ω20W), the speaker plate is 12mm thick, the inner asphalt is damped, the outer spray is blue piano lacquer, with net cover.
Using the power amplifier of Figure 1, combined with the two-way bookshelf speaker, the signal source uses the new 280 DVD player, and replays a song "in that far away place". The treble is crisp and bright, the penetrating power is strong, the bass is full and round, and the sound is soft and resistant. Listening, quite "daring". The level of the electronic crossover amplifier, the wideness of the frequency response, the large dynamics, the high resolution, and the high transient are greatly unexpected, fully demonstrating the unique and charming charm of the electronic crossover amplifier.
Third, the motor machine method. If you think that the LM4766 has low power, you can use TDA7294 or LM3886 to replace it. The performance will be further improved. The tone board can also be replaced with the LM4610. The front stage can be added to the XR1075 audio enhancer and the QS7779 virtual Dolby surround processor. If you want to save costs, you can also use 4 LM1875 to form an electronic crossover amplifier, but the LM1875 is more noisy when playing at high power.