Tberg I agree that the current is constant where at the portion of voltage is being converted as heat and other as output power.
lets consider we have the power output of 100W then V across load is 28.28V and current is about 3.53A in load. Now how do we calculate the voltage supply after rectification? considering the losses and heat..
lets consider we have the power output of 100W then V across load is 28.28V and current is about 3.53A in load. Now how do we calculate the voltage supply after rectification? considering the losses and heat..
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If the output current is 6.5A this will induce 3.25A continous for the two rails since each rail is supplying the speaker 50% of the time alternatively, hence the average current per rail is 6.5A/2....
Of course , each rails will provide 6.5A current to the speaker but that
is an instantaneous value as the current is either sinked from the positive
rail or the negative one but never from both at the same time , one rail will provide
the 6.5A during 50% of the time and the other rail will be at use the other 50% ,
so the average current per rail is half of the instantaneous value.
is an instantaneous value as the current is either sinked from the positive
rail or the negative one but never from both at the same time , one rail will provide
the 6.5A during 50% of the time and the other rail will be at use the other 50% ,
so the average current per rail is half of the instantaneous value.
Hi, I have a question on the same subject but for a different purpose.
I mean...I'm building an amp (P101 by Rod Elliott) where protections and some other (monitoring) functions will be managed through a "digital" board equipped with a microcontroller.
Since the amp will be equipped with a 3.5" LCD, I would like to add also an output power meter "feature" to measure the power delivered to the speakers.
The first way, but more complex, is to use a true-RMS-voltage converter IC but it would involve serial communication between the micro and this IC and everything would get, as told, more complex.
To avoid complexity, could I calculate the power to the load as difference between the instantaneous power measured from the PSU and the power absorbed from the amp without signal?
In other words, can the instantaneous power provided from the PSU be approximated to the power provided to the speakers knowing the power absorbed without signal?
Thanks, regards.
Roberto
I mean...I'm building an amp (P101 by Rod Elliott) where protections and some other (monitoring) functions will be managed through a "digital" board equipped with a microcontroller.
Since the amp will be equipped with a 3.5" LCD, I would like to add also an output power meter "feature" to measure the power delivered to the speakers.
The first way, but more complex, is to use a true-RMS-voltage converter IC but it would involve serial communication between the micro and this IC and everything would get, as told, more complex.
To avoid complexity, could I calculate the power to the load as difference between the instantaneous power measured from the PSU and the power absorbed from the amp without signal?
In other words, can the instantaneous power provided from the PSU be approximated to the power provided to the speakers knowing the power absorbed without signal?
Thanks, regards.
Roberto
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please someone correct me if i am wrong:
in your case of 15A through 4r load one power supply rail gives 7,5A and the other the same in case of symetrical signal. if your transformer can deliver 8,9A that would be 17,8A through a speaker if one channel is powered,and than is a bit more than needed. if it supplies two channels,that transformer would be unsufficient and the most of time overloaded. again,please someone correct me if i am wrong...
Edit:just now i noticed that here is more than first page,typing from mobile...sorry...
in your case of 15A through 4r load one power supply rail gives 7,5A and the other the same in case of symetrical signal. if your transformer can deliver 8,9A that would be 17,8A through a speaker if one channel is powered,and than is a bit more than needed. if it supplies two channels,that transformer would be unsufficient and the most of time overloaded. again,please someone correct me if i am wrong...
Edit:just now i noticed that here is more than first page,typing from mobile...sorry...
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most commercial equipment save money by using a transformer VA rating less than the total maximum power output.
Forget about trying to determine transformer current from amplifier current.
The connection from one to the other is very complex. Look at Goottee's Thread for just how complex.
If you can get beyond that complexity and think about what the transformer rating is:
The VA rating, from which we can extract the current rating, ONLY applies when the transformer is feeding AC current to a purely resistive load.
That is NOT what happens when you rectify and smooth the output of a transformer.
Stay with the simple determination. VA~1.5times total maximum power.
Then measure the resulting ripple on the smoothing capacitors and decide if that meets your target for amplifier performance. Adjust if you are not happy.
The connection from one to the other is very complex. Look at Goottee's Thread for just how complex.
If you can get beyond that complexity and think about what the transformer rating is:
The VA rating, from which we can extract the current rating, ONLY applies when the transformer is feeding AC current to a purely resistive load.
That is NOT what happens when you rectify and smooth the output of a transformer.
Stay with the simple determination. VA~1.5times total maximum power.
Then measure the resulting ripple on the smoothing capacitors and decide if that meets your target for amplifier performance. Adjust if you are not happy.
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