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Audio transformers work in the audio frequency range over about 9 octaves (20-20,000Hz)
Useful for impedance matching and converting between balanced and unbalanced lines.
Disadvantages of transformers are weight and cost.
Audio Matching Transformers
Devices that use coils eg: microphones, guitar or piano pickups, have a low impedance 50-600 ohms. The impedance of an amplifier will usually be in the kilo ohms to mega ohms range. The mismatch results in loss of power which has to be compensated for with higher gain in the amplifier which will also amplify the noise.
Still used in professional audio applications where long leads from microphone to mixing board
Valve transformers
Used to match the high impedance (Kilo ohms) of a valve output to a lower impedance speaker (1 to 2000 ohms, usually 4-16)
Hybrid Coil
A 3 coil transformer that seperates the microphone and earphone signals in a telephone. Converts between 2 wire and 4 wire working which has to be done to amplify a telephone circuit.
I bought one audio transformer type TY-145P from Farnell. The input for the transformer is 9V square wave but the output is same with the input. Other than that, I wonder why both the primary impedance and the secondary impedance is same. Anyone can tell me how to use it?
You mean to step up the voltage, I will need to add one more power transformer at the output of audio transformer?
One more thing, I try to step up the 9V AC voltage with normal transformer, but there is no signal at the output. Is it because of the current is too small after being step down in the transformer?
No.
There is a difference between an issolation transformer and an impedance matching transformer.
An issolation transformer has a 1:1 primary to secondary winding so voltage/current in is voltage/current out it's simply there to issolate the signal from whatever might be driving it (perhaps it has a DC bias)
A step up or down transformer has a different number of primary to secondary windings, like 1:2 for a 5volt to 10 volt transformer, or you can hook it up opposite and get a 5 volt to 2.5 volt transformer. If voltage goes down the available current goes up and vice versa. The power you put in is the power you get out less transformer losses. Are you sure ytou're not applying a 9 volts DC signal? If you were applying an AC signal you'd get some kind of results on the output.
I am very sure that the input of the transformer is AC signal but it is square wave which I not sure whether it will affect the output or not. My transformer is about 1:25 primary to secondary winding which is much more higher compare to 1:2. I try to input the transformer with 15V from variable AC power supply and I can get the output.
As I have already stated you audio transformers aren't needed much nowadays. If you want to transform from one DC voltage to another you use a DC-DC converter.
All an isolation transoformer is, is a transfromer with an equal number of turns on the primary and secondary. Apart from this it isn't any different from any other transformer.
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