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#### ginetto61

Hi !

to have an idea of the real power of an amp I have always been told to look at the power consumption on the rear
But ,,, these are the ratings of the original transformer of an amp

31V-0-31V (3A each) and 18V-0-18V (O.4A each)

and 600W is what is reported on the back as the max power consumption

it is about 1/3 of the value stated on the official specifications (!)

Does this value refer to short circuit condition ?
How can this be possible ?
Thanks and regards,
gino

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#### Bigun

Paid Member
Power = energy flow per second

So you can have a low average power, but a high peak power. Manufacturers of amplifiers are in a competitive environment and consumers who buy amplifiers because of their power rating encourage manufacturers to state high power ratings - which they can do if they state peak power instead of continuous average power.

#### ginetto61

Thanks a lot.
But I cannot find in the specs of transformers this peak power
Just the average I think
Isn't it strange ?
Thanks again,
gino

#### DF96

Does 600W come from RMS mains voltage multiplied by RMS mains current? Not a sensible calculation, as they are different waveforms, but you can't assume that whoever decides what to print on the back panel understands electronics.

#### picowallspeaker

I was asking the same questiom the other day and the answer was :
see if you can measure transformer's core section.
I did, and it was 2,5 X 3 cm ; on the back of the amplifier it was stated 310 W
max consumption.
The reply was : it can hardly produce 30 W

#### ginetto61

Does 600W come from RMS mains voltage multiplied by RMS mains current? Not a sensible calculation, as they are different waveforms, but you can't assume that whoever decides what to print on the back panel understands electronics.

From what I understand the 3A are in the secondaries .. not in the primary
So I should multiply 3x31x2 (leaving aside the low voltage windings)
But this is what Talema sells as a 200VA transformer ... not a 600 one

You say you can't assume that whoever decides what to print on the back panel understands electronics
I am pretty sure they understand electronics very well
It is me the confused one ... unfortunately
I think I will look at the size instead
I see that the size tends to be similar for similar VA
Regards,
gino

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#### wahab

The max power comsumption is forcibly the level at wich the amp s
main fuse goes open circuit...

In the OP exemple there must be a 2A or so main fuse that will
be fused at about 600W input power , whatever the cause of such high
absorbed power , be it the transformer that got two shorted
windings or the amp outputs that are shorted.

#### ginetto61

I was asking the same questiom the other day and the answer was :
see if you can measure transformer's core section.
I did, and it was 2,5 X 3 cm ; on the back of the amplifier it was stated 310 W
max consumption.
The reply was : it can hardly produce 30 W

Actually in cheap amps the transformers and the power caps are usually undersized and low grade types
Unfortunately is a key section for performances
Buona serata
gino

#### ginetto61

The max power comsumption is forcibly the level at wich the amp s main fuse goes open circuit...
In the OP exemple there must be a 2A or so main fuse that will
be fused at about 600W input power , whatever the cause of such high
absorbed power , be it the transformer that got two shorted
windings or the amp outputs that are shorted.

So my method was plain wrong
I will keep this in mind. Thanks a lot !
Regards,
gino

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