# Can you tell me output ampere of the transformer?

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#### anirban420

Hi all,
I am going to make a 7.1 home theater system. I have some confusions regarding the designing of some parts of it. I will state every problem of mine here and will expect a good solution. In this thread I will discuss about the designing of the transformer.

I am giving the schematic of the transformer below. Can you tell me what should be the Ampere rating on the secondary winding of it?

Anirban

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#### anirban420

Thanx for the early reply @ Pano. Actually I am a hobbyist, therefore I may lack some theoretical concepts.

Firstly, I am giving you answer of the second question. RL1 will be the loads for the satellite channels. I am thinking to use four TDA4765 (2x30W) for this. RL2 will be the load for sub channels. This may be two TDA4780, each in a bridge mode.
Now the 1st question. I know that RL1 will draw 11A current and RL2 will draw about 8A current. My question is what should be the ampere rating of the transformer when RL1 and RL2 are simultaneously active? Is it 11A+8A=19A or it is overall 11A transformer?

19 amps.

#### jan.didden

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The transformer has to deliver the total power, so should be rated for that.
The smaller secondary must deliver the total current so that one should be rated for the current, but that's normally just the wire size. Same for the outer secondary where the wire size can be less.

What I would do is find a transformer for the rated power and voltages and check what the max secondary currents are.
You probably will not easily find a 2X10/14VAC transformer, more likely two different secondaries or maybe even need to get two transformers.

jan

#### anirban420

Ya I understood the problem. I am now thinking to have three separate transformers. One is for the satellite channels only, it would rate 20V-0-20V, 11A. and the other two are for the two subs, those will rate 28V-0-28V, 4A each. I am thinking to mount sub transformer, pcb and all the stuffs inside the sub box and separate amplifier module for satellite channels.

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