Modular Amplificador TDA7293 en modo bridge - paralelo

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Modular Amplificador TDA7293 en modo bridge - paralelo

Mensaje sin leer por Enigma » 09 Mar 2019, 11:04

Modular Amplificador TDA7293 en modo bridge - paralelo

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The final amplifier have output power between 70W and 300W for 4 and 8 ohm speakers. Three several modules required for this project if bridged and paralleled modes required. The 4th module is the speaker protection. The amplifier can be built as:

Single amplifier with only one module with 1 TDA7293 or TDA7294 / channel
Bridged amplifier with 2 modules / channel
Paralleled amplifier with 2 modules / channel
Combined bridged and paralleled with 4 modules / channel
Paralleled simple or bridged amplifier, but with 2 paralleled module.

General remarks
A good amplifier begins with a high quality power supply. It should be capable to supply high currents while maintaining a stable voltage. Use therefore a toroid transformer. It should preferentially be potted to reduce hum. Long lasting low esr capacitors (e.g. BC components 051 or 056 series, Panasonic FC) should be used to smooth the rectifier output. The last important ingredient is proper grounding.

If in the application, the speakers are connected via long wires, it is a good rule to add between the output and GND, a Boucherot Cell, in order to avoid dangerous spurious oscillations when the speakers terminal are shorted. The suggested Boucherot Resistor is 3.9W/2W and the capacitor is 1µF.

Make sure to use the schematic from the datasheet from 2003. Slave mode is activated by pulling IN+, IN- and SGND to -Vs, the negative supply! In older versions of the schematic slave mode is NOT activated properly, which may lead according to reports on the internet to the destruction of the chip.

Enhancing low frequency performance
The low frequency performance of the TDA729X is poor, if used according to the datasheet. The sound is somewhat "thin" in the low frequency range. The reason is that the lower -3dB frequency of the input capacitor (C1, 470nF) and the corresponding resistor to ground (R1, 22k) is around 35Hz and that of the feedback network (R3, 22k; R2, 680ohm; C2, 22µF) is about 25 Hz.

If you increase the input capacitor C1 to 2.2µF the roll of frequency drops to 4Hz and with value of 100µF for the feedback DC decoupling capacitor C2 the -3dB point of the feedback network is around 3Hz. Now the frequency response becomes nicely flat:

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The modules can be connected with 15 pin connectors instead of wires. The single, bridged, and paralleled amplifier modules are not same, one for the first and the most important "main" module, one for bridge connection, and one for parallel connection what can be used for both main and bridged modules. The last 4th module is the speaker protection, must be placed to the middle of stereo configuration between left and right channels.

The official datasheet contains all modes of TDA729x circuits. The TDA7294 is very cheap, but cannot use for paralleled mode, and no clipping led output. The recommended max. power supply voltage is +-40V. The TDA7293 have paralleled mode (where only the power stage works, the preamp stages off), the max. power supply voltage is +-47V, and clipping led output available. The maximum output power of one circuit is 70-75W of TDA7294, and about 80-100W of TDA7293.

The possible output powers of bridged application:
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The V column is the power supply voltage, 1 means: 1 IC paralleled, 2 means: 2 IC paralleled with all others. Without superscripted number have no parallel connections, this is only bridged.

The possible output power with single (non bridged) application:
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The V is the power supply voltage, 1 means: 1 IC paralleled, 2 means: 2 IC paralleled. Without superscripted number have no parallel connections.

The bridged or single version is very popular on "official" instrument amplifiers. Carlsbro GLX100, Marshall MG, and Marshall Mode Four contains TDA7293/7294 circuits.

The four modules (including speaker protection) can be connected by the 15 pin connectors soldered to the edge of the PCB. This is the method to build single, bridged, paralelled, bridged+paralleled, bridged+duble-paralleled, mono or stereo applications with very simple easy to build PCBs.

The first and the most important circuit is complete 70-75W amplifier:
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This circuit always be the first of the complete amplifier configuration, which can be continued with parallel, bridge, or speaker protection module.

The PCB of main TDA module:
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To the Conn2 on right edge can be connected another module for bridged or parallel application. It this one main module required (for 75W output power) then Conn2 can be used for speaker protection, but this is not required. The nother side have Conn4 connector for the second (right) channel is the setup is stereo. This Conn4 connector can be connected the speaker protection only. For example the simplest stereo setup is: 1 main module for left channel, 1 speaker protection, 1 main module for the right channel. Examples are on the PDF manual. The speaker protection will be protected bot left and right channels.

On this first PCB the Conn5 connector is the stereo audio level inputs, the right channel wired to the input of another main module on the right side of speaker protection. The output connector Conn6 is not stereo. This connector can be user for one channel only (the another output is on the second main module). The single setup uses Out+ and GND, the bridged setup uses Out+ and Out- for speaker connection.

The second circuit for bridge configuration:
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And the bridge PCB:
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The Conn4 connector of this bridge PCB can be used for the connection of first main circuit. This module can be continued by Conn5 connector with speaker protection (if the channel finalized) or with parallel module if more output current needed.

If the setup must be continued with parallel mode, here is the schematic:
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PCB for parallel mode:
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This is the simplest module, because the premaplifiers are off within the circuit, only the power FETs working. This mode controlled by Buffer Driver and Slave mode pins of TDA circuit. This module can be connected to the right side of main module, bridge module, or if required can be connected to the parallel module to duplicate the paralleled circuits within the application. The second parallel modules can be continued with speaker protection or with nothing only. The another edge of the speaker protection (if used) can be restart the full setup with main module for right channel.

The speaker protection:
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And the PCB:
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Here are the examples how to build complete amplifiers with several output powers with these four modules. The "Module 1" is always the first and always required main module, the "Module 2" is the optional bridge module, "Module 3" is the optional parallel module can be duplicated within the setup, and the 4th is the speaker protection.

The simplest mono setup (75W on 4 Ohm, with 8 Ohm about half):
Module 1
Speaker protection (optional)

Simple stereo setup (2x 75W on 4 Ohm, with 8 Ohm about half):
Module 1
Speaker protection (required)
Module 1

Mono bridged application (8 Ohm only, about 150W):
Module 1
Module 2
Speaker protection (optional)

Bridged stereo setup (8 Ohm only 2x150W)
Module 1
Module 2
Speaker protection
Module 1
Module 2

Mono paralleled setup (4 Ohm about 100W):
Module 1
Module 3
Speaker protection (optional)

Stereo paralleled setup (2 x 100W on 4 Ohm):
Module 1
Module 3
Speaker protection (required)
Module 1
Module 3

Mono bridged and paralleled (4 Ohm - 300W, 8 Ohm 200W):
Module 1
Module 3
Module 2
Module 3
Speaker protection (optional)

Stereo bridged + paralleled setup (About 2 x 300W on 4 Ohm):
Module 1
Module 3
Module 2
Module 3
Speaker protection
Module 1
Module 3
Module 2
Module 3
The parallel module can be connected to the first parallel module for duplication. This increases the maximum current, maybe smaller output impedance possible.

Doubled parallel bridge setup:
Module 1
Module 3
Module 3
Module 2
Module 3
Module 3
and the upper setup can be continued with speaker protection and the another edge of speaker protection can be repeated the same setup for right channel is stereo application required.

Low Frecuence
It is recommended to increase the value of the bootstrap capacitor C5 to at least 47µF per chip to improve low frequency performance further.

Recommended capacitances for the input capacitor C1 include Wima MKS-2 2,2µF 50V DC (metallized polyester foil) and for the feedback DC decoupling C2 and the bootstrapping C5 Panasonic FC 100µF/35V (aluminium electrolytic capacitor, low esr, 105°C).

Failure in the official datasheet of TDA7293
The original datasheet of TDA7293 is not correct. The 10th page for parallel module is wrong on the first version created at 1999. If you seek the datasheet by google, you may find this older version first. You have to use new datasheet created at 2003. Here is an article about this problem (and my own paralleled TDA amplifier by the datasheet 1999 was wrong like in the article):

"Make sure to use the schematic from the datasheet from 2003. Slave mode is activated by pulling IN+, IN- and SGND to -Vs, the negative supply! In older versions of the schematic slave mode is NOT activated properly, which may lead according to reports on the internet to the destruction of the chip."



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