Design an audio transformer for an amplifier for the purpos of Impedance matching

[f.nasr]

Hi friends,
I am new on the forum and hope to learn a lot here. I want to design an audio transformer for an underwater acoustic power amplifier for the purpose of Impedance matching. I want to know how to calculate turns, impedance, watts, etc. Unfortunately there are few literature surveys on this issue. I have glanced at Wolpert’s audio transformer design manual. But there are still some vague points, e.g. I have not found an equivalent circuit for the audio transformer to know exactly know what elements it is made up of and how they are joined to each other. I have also found a software named OPT Design Assistant. I have a lot of doubts about the correct way to use it. Even if I knew how to use it, I would not be able to design the audio transformer. Because, as mentioned before, I have not found an equivalent circuit for the audio transformer. Now I am seeking your help; any info about the problem will be very useful to me. Any help is also appreciated.
Thanks a lot, f.nasr

 

[FvM]

Audio transformers undergo the same laws as mains transformers. https://en.wikipedia.org/wiki/Transformer
If you understand the basic formulas how voltage, current and impedance gets transformed, you can calculate most aspects of your audio transformer.

Two special points should be mentioned:
- low frequency full power limit
The ability of a transformer to transmit low frequencies with a certain voltage level is limited by the core saturation flux. Respectively an audio transformer has to be designed for the lowest frequency that must be handled with full power. E.g. if you decide for a lower frequency limit of 25 Hz, the transformer must have double the turns per volt as a 50 Hz mains transformer.
- high frequency cut-off
The leakage inductance of the transformer causes an amplitude drop of the loaded transformer at higher frequencies. A regular transformer design doesn't achieve much more than a 1:100 frequency range. For full 1:1000 audio range, you'll need to build the transformer with interleaved windings.

 

[chuckey]

A wideband high power audio transformer is very expensive, are you sure that you need one?. I not not think that they are actually used now in audio amplifiers.
Frank

 

[Audioguru]

Do you want the transformer to match the impedance of an underwater transducer (speaker?) to the output of a vacuum tubes (valves) amplifier?
It was common 60 years ago because a speaker has a low impedance and a vacuum tube has a high output impedance.

But today a solid state amplifier has an output impedance of 0.04 ohms or less so it drives a low impedance speaker perfectly and its very low output impedance damps speaker resonances. The full power of the amplifier drives the speaker.
If you use a resistor in series with the solid state amplifier output then it will match the speaker impedance, will throw away half the output power and cause a boomy resonant sound. Then a transformer is not needed.

Please post the detailed spec's of your transducer.

 

[f.nasr]

A wideband high power audio transformer is very expensive, are you sure that you need one?. I not not think that they are actually used now in audio amplifiers.
Frank

Thanks for your wise answer;So what do you suggest for the impedance matching (a practical solution)? Please give me the detailed information about the solution; Thanks again.

 

[chuckey]

We need to know the impedance of the load, what power amp you are using and the bandwidth that will be needed, and the power level.

 

[Audioguru]

what do you suggest for the impedance matching (a practical solution)?

I asked you but you did not post the detailed spec's of your underwater transducer (speaker) so we do not know its impedance.
I found some in Google that are piezo so they have a high impedance that changes when the frequency changes, they are not a low impedance like the voice coil of a speaker.

Maybe that is why you need a transformer to match the impedance and equalize the frequency response.