Reference link: Wikipedia.org-->Bridged and Paralleled Amplifiers
I am stating it from wiki:
"The x 4 myth
It is sometimes stated, usually on internet forums, (and previously here on WikiPedia) that operating an amplifier pair in bridge mode can give four times the power (of one of the pair).
Reference may be made to the fact that power is proportional to the square of the volltage, implying that if the output voltage is doubled – as it is in bridge mode – then the power available increases by a factor of four.
This would only true if the current available could also double – as it would if the output impedance of the amplier stages was zero. But it is not; our 4ohm output impedance amplifier pair now presents as a mono amplifier with an output impedance of 8 ohms and no more current is available from each amplifier than when working singly.
In actual use, there is just one circumstance when x4 power can be achieved. This is when each of the amplifiers are rated at full output for an impedance that is lower than the connected speaker.
eg. 8 ohm speakers are very common and many amplifiers are rated down to 4 ohms. An 8 ohm speaker connected to such an amp would only be capable of using HALF of the available power. When two such amplifiers are bridged, the new output impedance is then 8 ohms and full power can be output to a 8 ohm speaker. (if the speaker is rated to accept it)"
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I have a Logitech Z-2300 where two STMicroelectronics TDA7296 are bridged together to power the sub. The power supply of Z-2300 is capable to deliver +/- 26.4 VDC, the current being 3.75 A. It sums up to 40W from each chip.
Now my question is, Bridging this two TDA7296 will produce 40 X 4 = 160W or just 40 X 2 = 80W only.
The sub bass driver is rated at 8 ohms. Ditto the two satellites.
Principles of Amplifier Operation in Z-2300:
1) A stereo audio signal comes in through the green 3.5mm audio connector with the control pod.
2) In the control pod, the signal passes through the main volume logarithmic potentiometer for attenuation.
3) This attenuated audio signal is then send down from the control pod to the subwoofer enclosure through a D-Sub connecter where the amplifier module exists. A JRC-4565 operational amplifier first receives this audio signal. The JRC-4565 having stereo handling capability distributes the audio signal into two places:
a) To the left and right satellite TDA7296 power amplifiers and then subsequently to the 2 satellite speakers.
b) Back up to the remote through the D-Sub connector.
4) Inside the remote, the stereo audio signal is split again:
a) To the headphone jack
b) To the subwoofer bass volume potentiometer (where it is combined to mono at this point)
5) Audio signal output from the subwoofer bass potentiometer finally gets fed back into the subwoofer enclosure through the D-Sub connector to the bridged TDA7296 subwoofer power amplifiers and then to the bass driver.
I wish the TechGurus will help me.
Regards, RishiGuru
I am stating it from wiki:
"The x 4 myth
It is sometimes stated, usually on internet forums, (and previously here on WikiPedia) that operating an amplifier pair in bridge mode can give four times the power (of one of the pair).
Reference may be made to the fact that power is proportional to the square of the volltage, implying that if the output voltage is doubled – as it is in bridge mode – then the power available increases by a factor of four.
This would only true if the current available could also double – as it would if the output impedance of the amplier stages was zero. But it is not; our 4ohm output impedance amplifier pair now presents as a mono amplifier with an output impedance of 8 ohms and no more current is available from each amplifier than when working singly.
In actual use, there is just one circumstance when x4 power can be achieved. This is when each of the amplifiers are rated at full output for an impedance that is lower than the connected speaker.
eg. 8 ohm speakers are very common and many amplifiers are rated down to 4 ohms. An 8 ohm speaker connected to such an amp would only be capable of using HALF of the available power. When two such amplifiers are bridged, the new output impedance is then 8 ohms and full power can be output to a 8 ohm speaker. (if the speaker is rated to accept it)"
---------------------------------------------------------------------------------------------------------------------------
I have a Logitech Z-2300 where two STMicroelectronics TDA7296 are bridged together to power the sub. The power supply of Z-2300 is capable to deliver +/- 26.4 VDC, the current being 3.75 A. It sums up to 40W from each chip.
Now my question is, Bridging this two TDA7296 will produce 40 X 4 = 160W or just 40 X 2 = 80W only.
The sub bass driver is rated at 8 ohms. Ditto the two satellites.
Principles of Amplifier Operation in Z-2300:
1) A stereo audio signal comes in through the green 3.5mm audio connector with the control pod.
2) In the control pod, the signal passes through the main volume logarithmic potentiometer for attenuation.
3) This attenuated audio signal is then send down from the control pod to the subwoofer enclosure through a D-Sub connecter where the amplifier module exists. A JRC-4565 operational amplifier first receives this audio signal. The JRC-4565 having stereo handling capability distributes the audio signal into two places:
a) To the left and right satellite TDA7296 power amplifiers and then subsequently to the 2 satellite speakers.
b) Back up to the remote through the D-Sub connector.
4) Inside the remote, the stereo audio signal is split again:
a) To the headphone jack
b) To the subwoofer bass volume potentiometer (where it is combined to mono at this point)
5) Audio signal output from the subwoofer bass potentiometer finally gets fed back into the subwoofer enclosure through the D-Sub connector to the bridged TDA7296 subwoofer power amplifiers and then to the bass driver.
I wish the TechGurus will help me.
Regards, RishiGuru
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