Use the parallel stabilized power supply + discrete class A pre-stage to exert the ultimate effect of TDA7293

The author of the power amplifier in this article is named ME-7293 combined power amplifier. The schematic diagram is shown in the figure above: the discrete component class A bile taste pre-circuit is designed based on the principle of "simple is the most beautiful" Hi-Fi fever. The single-ended Class A circuit has few components, but after careful selection and precise setting of negative feedback, its effect is very outstanding, mainly manifested by the soft tone orientation, natural, rich musical taste, and excellent bile taste. Used with TDA7293 post grade, its effect is very outstanding! The principle of the pre-stage circuit: the input stage is composed of the field effect tube K246 (VT1, VT2) and C2240 (VT3) to form a differential amplifier input stage with a constant current source. The reference voltage on the base of VT3 is divided by R7 and VD1, VD2 Provided, the stability of the pre-stage circuit is better. The advantage of using the field effect tube as the input stage is that the input impedance is high, which is conducive to the pickup of weak signals. Its transmission characteristics are very similar to the electron tube, and can show the similarity of the amplifier. Timbre. The voltage amplifier stage is composed of VT4 and VT5. Toshiba fever famous tubes A970 and C2240 with extremely low noise and good high frequency characteristics are used. A970 and a constant current source composed of C2240 form a single-ended Class A output stage (quiescent current 6mA, so The output stage works in the Class A state), because the single-ended Class A output stage itself has the ability to cancel odd harmonics, making this pre-stage more amply. The tone part is composed of resistance capacitance, potentiometer and NE5532 (ne5532 can be directly replaced with the best op amp if you want better-AD827 can be used) This pre-stage is equipped with a through switch K, when you like to listen to pure music, click to lock Switch K can skip the tone part and output directly from the previous stage.

The discrete components used in the front stage and the power amplifiers used in the rear stage are commonly used in domestic fever. For example, the TW-200MK â…¡ type integrated power amplifier (priced at 1200 yuan) designed by Wu Gang of Beijing Tsinghua University adopts this structure. The Class A amplifier circuit can cancel the odd harmonic distortion. Since the transistor always works in the linear curve, there is no problem of switching distortion and crossover distortion. The beauty of its timbre is believed to have heard too much fever!

In order to exert the ultimate effect of TDA7293, I designed TDA7293 as a current and voltage dynamic negative feedback type (with DC servo), including the speaker system in the feedback network, which plays an active role in controlling the speaker and effectively cancels the speaker vibration The resulting distortion greatly enhances the bounce of the music, makes the rigid sound in a single plane sound field become lively and angry, the sense of space is enhanced, and the width and depth of the sound field are significantly improved! It can well take into account the problems of nonlinear distortion and transient distortion in the power amplifier. Make the sound quality of the power amplifier more attractive, such as warm and elastic sound, clear and transparent midrange, strong low-frequency dynamics, powerful bursting, accurate positioning of vocals and violins, high resolution, and sound that is audible and not annoying.

In order to solve the digital music source (such as CD, VCD, DVD, etc.) digital music dry and hairy, the TDA7293 power amplifier circuit in the figure has a softening effect on digital sound, which can soften the forward hair of the digital sound source. The function of this is to make the hard sound music music. This function is that the cf1 and cf2 in the circuit in the figure are the high-frequency AC gain compensation network, and its role is to reduce the digital sound (for high-frequency overtones above 60-80KHz To compress or weaken). IC2 in the figure is the role of DC servo.

The purpose of component selection: good circuit design and the use of high-quality components can maximize the effect! ①The coupling element has the greatest influence on the sound quality. The signal coupling uses WIMA MKP polypropylene non-inductive capacitor. The input stage volume control of this pre-stage uses Japanese ALPS potentiometer. The potentiometer of the tone part uses WL or XT brand. ②The resistance adopts imported metal film low-noise precision (± 1%) five-color ring resistance, its noise is very low; ③The electrodeless capacitor uses Dutch Thomson MKP polypropylene non-inductive capacitor; ④The circuit board uses silver-plated glass fiber epoxy board (Benefits of silver plating: prevent oxidation, reduce the resistance of solder joints, which is conducive to improving the analytical power of small signals), and use tin plating design at high currents (reduced resistance and enhanced ability to conduct current), The circuit board is printed with blue oil for high-grade.

Assembly amplifier application: The circuit in the figure is two-channel, and the power supply part is made on another circuit board. The advantage of this is that it reduces the interference of AC power, which is conducive to improving the signal-to-noise ratio. Keeping the power supply away reduces AC interference, so that a good power amplifier can be made. Here we recommend a suitable solution for AV and Hi-Fi: virtual Dolby surround sound processing circuit QS7779 → BBE circuit (BA3884) → ME7293 combined power amplifier board, plus 400W dual 26V + dual 12V ring cow. ▲ When assembling, please pay attention to the grounding method and the input and output grounds must be separated to the power ground to be connected. ▲ The above schemes are actually selected and deleted according to hobbies and applications. Adding the case is a high-quality power amplifier. And increase the fever experience, feel the intimacy of their assembly! A sense of success!

The audition equipment is as follows: the sound Ya S3 HDCD machine is used as the sound source. The speakers are made of Huiwei R1C + SS6N self-made bookshelf monitor speakers. Several CD CDs that are used to listening are selected for comparative audition. It is obvious that the sound quality of the ME7293 integrated amplifier is unique: Wide, particularly dynamic, excellent music positioning, excellent resolution, low frequency control (retractable), overall rich sense of layering, high-frequency slenderness, sweet and round mid-frequency, beautiful and beautiful, especially when playing genuine Hugo CD At that time, the singer's tooth sound and the sound of breathing were clearly audible, fully reflecting the advantages of the single-ended Class A pre-stage circuit with Hi-Fi high-power DMOS set-TDA7293! The details are vivid, the treble is silky smooth, and the sound quality is very pure! Her spotless tone will definitely make you unforgettable!

I won't say much about the beautiful playback test of the ME7293 integrated amplifier. Please let the enthusiasts experience it for yourself! That sound quality charm is great!

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