What are audio transformers?

Audio transformers are recognized as “wide band” transformers. In real meaning a “transformer” is two or more windings attached by a common magnetic field. It is this magnetic field, which offers the means to pass the voltages and currents from any primary winding to the accessible secondary winding when alternating current that flows. Basically the chief purpose of an inter stage audio transformer is to isolate the DC and attached the signal, with minimal loss. The transformer windings looks like short circuit to DC, still are seen as complex impedances to the AC signal.

Much that follows on the topic of audio transformers is of need rather over cut down to give a universal overview. Audio transformers were actually used in valve or tube amplifiers as inter stage and in any output transformers. Early transistor amplifiers likewise used audio transformers for pairing and output stages.

There is nothing specifically spiritual about audio transformers even though their use is not for the most part widespread today. It is expected the most interest comes from people paying attention in restoring or construction tube audio amplifiers. Basic requirements should be considered first.

We should assume loyalty is primary in the minds of most restorers. Therefore the prime need have to be a comparatively huge bandwidth; this is in the audio sense. Resistance coupled amplifiers basically create undistorted output signal voltages regardless of plate load resistance value. Audio transformer coupling is basically applicable to power stages for impedance matching.

Maximum output power is created when the impedance of the load matches the plate impedance of the tube. Using triodes, to some extent less output power but considerably less distortion results when the load impedance is among two or three times the plate impedance.

However tetrode or pentode tubes have extremely high plate impedances and the first impedance of the combination transformer is often among 1/10 to 1/5 of the tube plate impedance as it not totally possible to make audio transformers with primary impedances beyond 20K. As Audio transformer mixture is on the whole appropriate to power stages for impedance matching