DIY Audio 300 Watt IC TDA7294 Chip Power Amplifier Circuit for Home Stereo or Subwoofer
TAKE A LOOK THEY USE 4 OHM SPEAKER WITH TDA7294 IN BRIDGE MODE THEY SAY IT`S 300WATT..!!!!!!
TAKE A LOOK THEY USE 4 OHM SPEAKER WITH TDA7294 IN BRIDGE MODE THEY SAY IT`S 300WATT..!!!!!!
The datasheet says 70 W RMS at 0,5 % distortion into 8, 6 and 4 ohms. (100 W is "music power" at unlimited distortion for a limited time.)
A bridged amp doubles the voltage swing, which may quadruple the power, if the amp and power supply can deliver the current. In other words, the TDA7294 could conceivably produce 4x70 W = 280 W RMS when bridged. But it does not have the current capacity, and it is not able to get rid of the resulting heat. Notice that the power is the same into 8, 6, and 4 ohms load. The data sheet only promises 150 W if bridged across 8 ohm load, and the distortion will start rising sharply from 100 W.
Bridging across a 4 ohm load effectively creates a 2 ohm load for each amp. The TDA7294 cannot drive lower impedances than 4 ohms, according to the data sheet, so there is no way you will get good results, much less 300 W power, by bridging these amps across a 4 ohm load. It will distort like mad.
As to the link that started the thread: No way. Meaningless numbers.
A bridged amp doubles the voltage swing, which may quadruple the power, if the amp and power supply can deliver the current. In other words, the TDA7294 could conceivably produce 4x70 W = 280 W RMS when bridged. But it does not have the current capacity, and it is not able to get rid of the resulting heat. Notice that the power is the same into 8, 6, and 4 ohms load. The data sheet only promises 150 W if bridged across 8 ohm load, and the distortion will start rising sharply from 100 W.
Bridging across a 4 ohm load effectively creates a 2 ohm load for each amp. The TDA7294 cannot drive lower impedances than 4 ohms, according to the data sheet, so there is no way you will get good results, much less 300 W power, by bridging these amps across a 4 ohm load. It will distort like mad.
As to the link that started the thread: No way. Meaningless numbers.
Very true.
I know for a fact that bridged 7294s can run a 6 ohm load no problems (the Logitech Z5500 has a 6 ohm woofer), but if you factor in power compression you realize that the impedance rises anyway when the system is played loud for extended periods of time, so it'll still be driving a 8 ohm+ nominal load thus no trouble.
Sure. The question is really how much power you can expect at a reasonable quality. If bridged gives 150 W into 8 ohms at decent quality and we assume that the chip is current/heat limited, dropping the impedance to 6 ohms will limit you to somewhere around 110 W with the same current, and dropping further to 4 ohms will leave you at 75 W. That is not much benefit over a single 70 W chip.
Also, heating the voice coil by playing loud for some time will reduce the efficiency of the speaker, so you will need some more power to keep the same sound pressure level. I would not bridge this chip for a 4 ohm load, and if I did, I would certainly not claim 300 W.
Also, heating the voice coil by playing loud for some time will reduce the efficiency of the speaker, so you will need some more power to keep the same sound pressure level. I would not bridge this chip for a 4 ohm load, and if I did, I would certainly not claim 300 W.
Hi,
bridging produces double the power into double the impedance.
This rule always applies. I do not know of any exception.
eg. a pair of 75W into 4ohm amplifiers when bridged will give a maximum of 150W into 8ohms.
But that 100W is identical to the sum of the maximum outputs of the two single amplifiers. i.e. 75W + 75W to drive two 4ohm loads is exactly the same as 150W to drive a single 8ohm load consisting to the original two 4ohm drivers connected in series.
Overall nothing powerwise is gained by bridging.
Personally I would use two drivers each with their own dedicated amplifier to give me the 150W of speaker input power that I desire.
bridging produces double the power into double the impedance.
This rule always applies. I do not know of any exception.
eg. a pair of 75W into 4ohm amplifiers when bridged will give a maximum of 150W into 8ohms.
But that 100W is identical to the sum of the maximum outputs of the two single amplifiers. i.e. 75W + 75W to drive two 4ohm loads is exactly the same as 150W to drive a single 8ohm load consisting to the original two 4ohm drivers connected in series.
Overall nothing powerwise is gained by bridging.
Personally I would use two drivers each with their own dedicated amplifier to give me the 150W of speaker input power that I desire.
IF (and that is a capital if) the amp can double its power when the impedance is cut in half, that also means that the amp could give four times the power into the same load when bridged. For example, a large power amp with a hefty power supply might be rated at 150 W into 8 ohms, 300 W into 4 ohms, and 600 W into 2 ohms. Bridged, the voltage swing across the load would be doubled and each amp would see one half the load (e.g., 4 ohms instead of 8). The result is that the load gets twice the voltage and twice the current, for four times the power.
Of course, this is all in theory only, since the 7294 gives the same 70 W into 4 ohms, 6 ohms, and 8 ohms. It just cannot cope with the needed current, and I agree with your game plan: Two separate amps driving two separate drivers, 4 ohm or 8 ohm. The added driver area would also give a useful contribution. Or dig up a single 16 ohm, high efficiency driver, bridge the amps, and get 170 W or so (again according to the datasheet). If the driver can give around 98 dB @ 1 W, that will also be plenty loud.
Of course, this is all in theory only, since the 7294 gives the same 70 W into 4 ohms, 6 ohms, and 8 ohms. It just cannot cope with the needed current, and I agree with your game plan: Two separate amps driving two separate drivers, 4 ohm or 8 ohm. The added driver area would also give a useful contribution. Or dig up a single 16 ohm, high efficiency driver, bridge the amps, and get 170 W or so (again according to the datasheet). If the driver can give around 98 dB @ 1 W, that will also be plenty loud.
Hi. It would be possible to design an amplifier which delivers 300 Watts RMS into 4 Ohm load using the TDA7294. It would need 4 x TDA7294 in bridged/parallel mode. The power supply voltages would need lowering and/or a current limiting resistor would need to be added to the output of each IC to prevent it from pushing out more current than it is designed to do.
It is possible, Marshall did in their MF350 guitar amp.
The amps burn so often that they had to offer a plug-in module so Musicians can repair them at home, that model stopped being carried by Music Shops because they did not want to deal with customer anger, and was quickly discontinued.
Pro Techs also avoid servicing them.
Go for any tried and true schematic, you'll find a few even here at DIY.
Does that answer your doubt?
The amps burn so often that they had to offer a plug-in module so Musicians can repair them at home, that model stopped being carried by Music Shops because they did not want to deal with customer anger, and was quickly discontinued.
Pro Techs also avoid servicing them.
Go for any tried and true schematic, you'll find a few even here at DIY.
Does that answer your doubt?
I would forget the chip amps and go for a proper class AB amplifier which is rated for high power.
Agree. Same here.
Besides, chipamps are great for providing a simple solution, fine.
But with 4 15 leg chipamps, you are reaching 60 pins total, just for them , plus auxiliary elements.
When proper robust versatile discrete amps become simpler than the unflexible chipamp solution, then chipamps lose a lot of their attraction.
Besides, chipamps are great for providing a simple solution, fine.
But with 4 15 leg chipamps, you are reaching 60 pins total, just for them , plus auxiliary elements.
When proper robust versatile discrete amps become simpler than the unflexible chipamp solution, then chipamps lose a lot of their attraction.
Max.mum voltage??
Hi, friends,
I was following your discussions and would like to ask few doubts. In the TDA7294 datasheet, when it comes to the bridged section, it is given that
Based on the above, I am getting confused on whether there is any restriction on the maximum voltage of the bridged circuit. My wish is to run bridged circuits (with 4 ics - 2 ics for left and 2 for right) for stereo applications, at 150 watts+ 150 watts, 8 ohms loads and 38+,0, 38- dual DC power supply. I know its a bit near the limit but I have run the non-bridged stereo version on a 2.1 amplifier at 38 volts dual DC. It is working fine. But, when it comes to bridging, I am still in doubt in implementing at that voltage.
If it proves to be a problem, I am planning to shift to TDA7293. Also, I would like to know if its ok to use 0805 package resistors for the resistors for TDA7294.
Hi, friends,
I was following your discussions and would like to ask few doubts. In the TDA7294 datasheet, when it comes to the bridged section, it is given that
When I looked into many circuits that are available for purchase, it was seen that most people restrict the voltage to a low value at bridging level.
Based on the above, I am getting confused on whether there is any restriction on the maximum voltage of the bridged circuit. My wish is to run bridged circuits (with 4 ics - 2 ics for left and 2 for right) for stereo applications, at 150 watts+ 150 watts, 8 ohms loads and 38+,0, 38- dual DC power supply. I know its a bit near the limit
but I have run the non-bridged stereo version on a 2.1 amplifier at 38 volts dual DC. It is working fine. But, when it comes to bridging, I am still in doubt in implementing at that voltage. If it proves to be a problem, I am planning to shift to TDA7293. Also, I would like to know if its ok to use 0805 package resistors for the resistors for TDA7294.
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If you bridge your stereo amp and use the same 8 ohm speaker, the voltage and current are both doubled giving you four times the power.
The voltage is only a problem if you touch the terminals (2xrailvoltage). The problem is that each amp and its PSU are expected to supply double the current.
To do this correctly, you should design the amps for 4 ohm use. This normally means replacing the PSU and transformer.
The voltage is only a problem if you touch the terminals (2xrailvoltage). The problem is that each amp and its PSU are expected to supply double the current.
To do this correctly, you should design the amps for 4 ohm use. This normally means replacing the PSU and transformer.
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