The smooth and delicate Hi-Fi high-power DMOS set successfully puts TDA7293

A new generation of round and delicate Hi-Fi high-power DMOS sets are successfully released

——TDA7293

Author: Mo Xiong love

In recent years, the design and production process technology has been changing with each passing day, and is widely used in various high-end audio and video products, such as LM3886TF, LM4766, TDA7294, etc. Here to introduce the readers to the new generation Hi-Fi high-power DMOS set with better sound quality and more power than TDA7294, and successfully put TDA7293.

The famous European SGS-THOMSON STMicroelectronics recently introduced a Hi-Fi high-power DMOS set with better sound quality than TDA7294 and more power to the country-TDA7293, which meets the needs of audiophiles in both sound quality High-power fever desires are widely used in home Hi-Fi amplifiers, home AV amplifiers, active speakers, etc.

The internal structure of TDA7293 and TDA7294 are basically the same, divided into three stages: the differential input stage is composed of bipolar transistors, and the driving stage and the power output stage use field effect transistors. This structure can integrate the low noise and power field effects of bipolar transistors The advantages of the tube in terms of linearity, temperature coefficient, and timbre, combined with rigorous production technology, make it have a very ideal objective test index. The sound is beautiful, taking into account the advantages of the bipolar signal processing circuit and the MOS power tube, and has the advantages of low distortion, low noise, high withstand voltage, mute switch, overheat protection, short circuit protection and so on.

The appearance and size of TDA7293 is the same as that of TDA7294. It is a 15-pin package. The function of each pin is the same as that of TDA7294. Only a few pins are different. The functions of each pin of TDA7293 are as follows: pin 1 is the standby ground; pin 2 is the inverting input terminal; pin 3 is the positive phase input terminal; pin 4 is the ground; pin 5 is CLIPDET; pin 6 is the bootstrap terminal; pin 7 is + V (Signal processing part); Pin 8 is -V (signal processing part); Pin 9 is the standby terminal; Pin 10 is the mute terminal; Pin 11 is BUFER DRIVER; Pin 12 is BOOT LOADER; Pin 13 is + V (power output stage) Part); 14 feet is the power output; 15 feet is -V (power output stage part).

The main parameters of TDA7293: working voltage range: ± 12V-± 50V; peak output current 10A; output power: 100W at ± 40V, 8Ω; 140W at ± 45V, 8Ω; 100W at ± 29V, 4Ω; total harmonic distortion (Po = 5W, f = 1KHz) 0.005%; conversion rate 15V / μs (TDA7294 is 10 V / μs, the higher the conversion rate, the richer the sound quality level); input impedance 100KΩ; frequency response 20Hz-20Kz; working in Class A and B.

In order to exert the ultimate effect of TDA7293, I designed TDA7293 as a current negative feedback constant current power amplifier (with DC servo) and as a two-channel speaker protection circuit (the purpose is to prevent TDA7293 from protecting the expensive speaker system if it is accidentally damaged, This is very important. The price of the TDA7294 integrated power amplifier board in the current mail order market is very different. Usually, the low price does not have an independent speaker protection circuit, only the protection function of the integrated block. This is something that enthusiasts need to understand. Mail order, don't be greedy and cheap, so as to avoid unnecessary losses), in order to prevent the interference of AC power on the signal, the author adopted a split design of power supply and power amplifier board. The quality of the power supply directly affects the sound quality of the power amplifier. Therefore, the author uses a dual-bridge rectifier (2 10A bridge stacks, which are better than single-bridge rectifiers for dual-bridge rectification, which suppresses hum to a greater extent). Only 10000uF plus 2 0.1uF, easy to deal with the needs of large dynamic! The schematic diagram is very simple, not drawn here.

The power amplifiers on the market no matter whether they are Class A or Class A or B, voltage-type negative feedback is used more, and current negative feedback is less. The output voltage of the voltage-type negative feedback amplifier is only related to the amplification factor, and it is related to the impedance of the speaker. Irrelevant, this makes the amplifier unable to overcome both nonlinear distortion and transient distortion. Using current negative feedback can solve this shortcoming: use the linear element resistance to sample the current flowing through the speaker voice coil and feed it back to the power amplifier input terminal, so that the amplifier drives the load in a fixed current mode, and the speaker can be very sound when it is oscillated by current control. Solve the problem that the nonlinear distortion and transient distortion in the power amplifier can not be taken into account. 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.

Figure 1 is the circuit schematic diagram of the current negative feedback constant current power amplifier using TDA7293 (only one channel is drawn in the figure, the other channel is the same), using current negative feedback, it also includes the speaker system in the feedback network , Plays an active role in the control of the speaker, effectively counteracts the distortion caused by the vibration of the speaker, significantly enhances the bounce of the music, makes the rigid sound in a single plane sound field become lively and angry, and the sense of space is enhanced, The width and depth of the sound field have been significantly improved.

In order to solve the digital music source (such as CD, VCD, DVD, etc.) digital music is hard and hairy, the circuit in Figure 1 has a softening effect on digital sound, can soften the sound of the digital sound source "hair" sound, To make hard sound music, this function is that the cf1 and cf2 in the circuit of Figure 1 are high-frequency AC gain compensation networks, and their role is to reduce digital sound (compress high-frequency overtones above 60-80KHz 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! ①WIMAMKP polypropylene non-inductive capacitor for signal coupling; ②Resistance adopts imported metal film low-noise precision (± 1%) five-color ring resistor, its noise is very low; Polypropylene non-inductive capacitor; ④ The circuit board uses silver-plated glass fiber epoxy board (the benefits of silver plating: prevent oxidation, reduce the resistance of the solder joints, which is conducive to improving the analytical power of small signals), printed with blue oil Transformation;

Assembly amplifier application: The circuit in Figure 1 is a dual channel without power supply part (the power supply schematic is very simple, not drawn here). The advantage of this is that the signal-to-noise ratio of the left and right channels is improved, and the assembly When the power amplifier is combined, the power supply can be kept away to reduce AC interference, so that a good power amplifier can be made. At this time, we recommend a suitable solution for AV and Hi-Fi: virtual Dolby surround sound processing circuit QS7779 → BBE circuit (BA3884) → tone circuit (ME-128 or KA-307 Class A pre-stage of Meishun Electronics Factory or SP-27 or LM4610N) → power amplifier board, plus 400W dual 26V 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. ▲ It is recommended to use it together with KA-307 Karaoke preamplifier or ME-128 Class A preamplifier for better sound quality.

For enthusiasts who want to assemble the power amplifier, the current negative feedback constant current power amplifier circuit of Figure 1 is a very ideal power amplifier, plus BBE, virtual surround, karaoke class A pre-stage, etc. 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: Marantz CD machine is used as the sound source. The speakers are made of Hivi 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 current negative feedback constant current made by TDA7293 The power amplifier is matched with the single-end pure DC class A pre-level sound quality: wide sound field, particularly good dynamics, excellent music positioning, excellent resolution, low frequency control (very freely), overall rich sense of layering, high frequency Slender, sweet and mellow mid-frequency, beautiful and beautiful, especially when playing a genuine Hugo CD, the singer's tooth sound and the breath of the breath are clearly audible, fully reflecting the single-ended pure DC class A pre-stage circuit with Hi-Fi high-power DMOS Set successful release-the advantages of 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 current negative feedback constant current power amplifier using TDA7293. Please let the enthusiasts experience it yourself! That sound quality charm is great!

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