Hi-Fi is the abbreviation of High-Fidelity in English, that is, high-fidelity, which means to faithfully restore the sound source information, that is, the original taste. This article introduces the reader to a high-fidelity fever Hi-Fi power amplifier combination. The total production cost is only a few hundred yuan. It is very easy to make and debug. It is very suitable for the production of music lovers of the majority of working class. The sound quality of this combination is extremely pure and transparent. Clear. Interested friends can make a set and compare it with thousands of machines on the market!
The schematic diagram of the Hi-Fi combination is shown in Figure 1: The audio source (CD, VCD, LD, DVD, etc.) is entered into the volume, tone, balance, equal-noise, and widening circuit LM1036N by the signal selection switch of the Hi-Fi combination. The expressiveness of the music signal is more natural, more realistic, and closer to the original taste. The music signal output by the LM1036N is input to the BBE2150AD sound effect enhancement and clear processor to intelligently restore the realistic sound signal (that is, the original taste), which is output by BBE The signal is amplified by the high-speed low-noise dual op amp "Emperor Emperor" NE5535N (produced by SigneTIcs in the United States, which is better than NE5532N, and enthusiasts also call it the United States S integration). Hi-Fi playback of music by left and right speakers.
Figure 2 is a typical application circuit of the signal input switching switch TDA1029. TDA1029 is a stereo four-channel high-fidelity sound source switching integrated circuit used by the Philips company for the audio field. Its operating voltage is 6-23V, typical value is 12V, and total harmonic distortion It is only 0.005%, and the signal-to-noise ratio is excellent (S / N = 120dB). It can be used to assemble or replace the signal selection switch of the power amplifier.
This Hi-Fi combination volume, tone, and balance control circuit uses National Semiconductor's (NS) high-quality tone circuit LM1036N. The LM1036N is a two-channel integrated circuit that uses DC level to control tone (high and low), volume, and balance. , The advantage of using DC level control is that the adjustment of high and low bass does not affect each other, the volume potentiometer is made of domestic ordinary products and there is no noise, the control is very smooth, LM1036N has frequency response compensation, wide range of single power supply (9-18V, typical value 12V) , High signal-to-noise ratio (input 0.3rns, 90dB) and other characteristics, is a fever-grade integrated circuit. LM1036N tone control range> 15dB, volume control range> 80dB, distortion is less than 0.03%. Figure 3 is a typical application circuit of LM1036N. NE5532N is a product of American SigneTIcs company. The function in the circuit is to amplify the signal and have a broadening effect (T2, NEH point shorting plays a broadening role, this function has a card effect Good) to suit the needs of different sound sources. For music lovers who already have a power amplifier, the volume and tone balance circuit of the original power amplifier can also be replaced by the circuit of FIG. 3, so that the sound quality of the power amplifier can be improved.
Hi-Fi means to realistically restore the sound source information, that is, the original taste. In addition to all the Hi-Fi-grade fever devices used in the Hi-Fi combination introduced in this article, the heroes who can truly achieve Hi-Fi are BBE technology. ! BBE is a sound effect enhancement and clarity technology introduced by the US BBE Sound Inc. to greatly improve listening quality. This technology restores the clarity of sound by making up for an inherent defect of speakers and headphones, giving the music signal a more natural, The more realistic reduction ability makes the musical expression closer to the original taste. The application fields of BBE technology include broadcast audio, professional audio, audiophile, and civilian audio (CD, VCD, LD, DVD, TV, etc.). BBE can be installed in any power amplifier and TV to upgrade its sound quality. The relevant BBE technology has been introduced in many electronic publications, so I will not describe it here. I now recommend the BBE circuit of BBE2150AD (see Figure 4), which I believe is good in all indicators and performance. BBE2150AD is a product of JRC in Japan. The working voltage is 4.5-13V, the typical value is 9V, and the working current is 9mA at 8mA. It has straight-through and BBE Features. The processing level of BBE can be selected in 2 levels. Figure 4 is its application circuit. This circuit uses reverse power supply protection and three-terminal voltage regulation. Therefore, when it is installed in various power amplifiers and TVs, it can take the power from the original machine. Without the need for additional power supply, it is very convenient to install.
NE5535N is used as the signal amplifier driving power amplifier of this Hi-Fi combination. NE5535N is a product of American SigneTIcs company. It is better than the high-speed op amp NE5535N. It has high open-loop frequency response, high unity gain bandwidth, and conversion rate. It is even higher than NE5535N, and is called by the enthusiasts as the "high emperor" of high-speed and low-noise dual op amps. NE5535N can directly replace 4558, 4560, LM833 and NE5532N, etc. The sound quality will be significantly changed after replacement. The sound quality is pure and transparent, and it is more clear. The application circuit of NE5535N is the same as NE5532N. I believe that the majority of audiophiles are already proficient. Circuit diagrams, needlessly occupy the layout.
As we all know, many power amplifiers have a power of about 100W × 2, but when they are used in homes, the volume is usually only about 1 / 5-1 / 4, that is, only about 10-30W. It is necessary to open the ears. If you suffer, you ca n’t stand it and it will distort the music. Therefore, households with dozens of square meters generally have “golden power†audio equipment around 30W. This article introduces the power amplifier circuit TD1514A designed by Philips for digital audio as the two-channel power amplifier circuit of this Hi-Fi combination (as shown in Figure 5, the other channel is omitted and not drawn in the figure, the other channel Same as the figure) TDA1514A has high output power: Pout = 50W (VP = ± 27.5V), high conversion speed: 15V / μs, excellent signal-to-noise ratio 85dB, ripple suppression 75dB, THD—0.08%, TDA1514A working voltage ： ± 9— ± 30V, TDA1514A circuit is equipped with waiting and mute state, with overheat protection, short circuit protection, power tube safe working area protection and electrostatic discharge protection. Low offset voltage, high ripple suppression, and extremely low thermal resistance. Application circuit Figure 5 The characteristics of the circuit: the use of constant current negative feedback and a DC servo system (the main circuit of the DC servo circuit is used to accurately correct the TDA1514A circuit to output DC potential drift after canceling the negative feedback DC blocking capacitor). A linear element resistance RA (0.5Ω2W) is used to feed back the current flowing through the voice coil of the speaker to the input of the power amplifier, so that the amplifier drives the load in a fixed current mode, and the speaker oscillates under the control of the current. The characteristic is that when the playback frequency reaches the low frequency and near the resonance peak, the constant current circuit enhances the strength of the bass and the resolution of the treble, so that the playback sound of the entire system sounds full, thick and clear, and has the charm of a tube amplifier .
The consistency of the successful batch amplification is fully guaranteed, and the biggest feature is the good stereo balance, which is far superior to the discrete component amplifier in terms of reliability and cost performance.
Component selection: In order to ensure that this Hi-Fi combination can achieve Hi-F level, the electrodeless capacitors in each circuit must use imported CBB metalized non-inductive capacitors, the coupling capacitors use Japanese advanced capacitors, and all resistors use 5-color ring precision (± 1%) Metal film resistors, integrated circuits must use genuine products, not cheap parallel imports.
Power supply part: In order to effectively improve the transient characteristics and high frequency characteristics of the whole machine, the front and rear power supplies must be powered separately. Practice has proved that the power supply characteristics of the pre-stage circuit have an important influence on the playback characteristics of the whole machine. Therefore, the TDA1029, LM1036N, BBE2150AD, and NE5535N all use an active servo power circuit for power supply. The characteristic of the active servo power circuit is that its output voltage is stable. The noise is extremely low, which can ensure the high-frequency characteristics and transient characteristics of the previous stage. Fig. 6 is the active servo power circuit.
Amplifier-level power supplies are believed to be familiar to the majority of audiophiles, so I will not give the circuit diagram here. The author recommends the use of 6A07 high current diodes such as 6A07 for the rectifier diodes. The filter capacitors should use large water tanks such as 6800UF-10000UF / 50V South Korean SANWHA Gold-printed capacitors. Gold-printed capacitors are dedicated for fever. Japanese black diamond rubies are also very good capacitors for fever. The power board is best to add a 3-5A fuse to ensure safety. Before and after the power supply can use a 200-300W dual 18V + dual 12V toroidal transformer, dual 18V is a power amplifier level power supply, rectified and filtered to obtain about ± 25.5V DC power supply, the use of dual 18V voltage as long as the mains does not exceed 260V, after rectification and filtering The voltage will not exceed the maximum operating voltage of TDA1514A ± 30V. The dual 12V of the transformer can be used by the active servo power circuit for rectification and filtering to supply power to the front TDA1514A circuit.
Assembly: The power amplifier chassis is currently on the market or can be obtained by mail order. The price is about 50-150 yuan. Depending on the chassis, there are different solutions. All circuits can be connected one by one in the order of the combined schematic diagram in Figure 1. However, it must be noted that the signal line must be made of high-quality screen, the power line should be thick and short, and pay attention to the method of grounding. This can prevent noise. The output of the TDA1514A and the speaker interface are added with a speaker made of professional silver contact relays. Protector to ensure the safety of the speaker.
If there is only one record player in the actual assembly, TDA1029 can be omitted. If there is a recording deck, you can install the LM1894N × 2 dynamic noise reduction board in the deck. To achieve a pair of speakers to produce a three-dimensional spatial surround sound field, a 3D sound field processor can be added between TDA1029 and LM1036N. If you want to combine this Hi-Fi to form a multi-channel power amplifier, you can change the volume tone board to UPC1892 Four-channel surround sound processor, and increase pre-amplifier and power amplifier (such as TDA1521, LM1875, etc.).
As long as the correct assembly and inspection are correct, you can listen to it. The author's audition feeling is that the Hi-Fi combination has extremely pure and transparent sound quality. It sounds warm, delicate, intimate and sweet. The overall bass strength and elasticity are good. The treble is clear and slender, creating a more natural and more musical signal. Realistic, is a real Hi-Fi amplifier combination.
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