J.W. Davis & Company

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Davis line transformers have insertion losses of about 1dB.  This translates into a power loss of 1.3 times the rated power of the transformer.  Thus, a Davis 4-watt transformer tapped at the 5-watt tap will consume around 6.5 watts of power.  The same transformer tapped at the 2.5 watt tap would consume 3.25 watts (1.3 X 2.5 watts).

Lower quality transformers typically have much higher insertion losses ranging from 2 dB to 2.5 dB despite the standard manufacturer's claim of 1.5 dB.  The table below provides a guide for estimating insertion losses.  Note that a 10-watt transformer with 2.5 dB of insertion loss would consume almost 18 watts of amplifier power (10 X 1.770).

The combination of line losses and transformer insertion losses are major consumers of amplifier power.  For example, a 25-volt system with an average line distance of 200 feet and using 18-gauge wire would have about 30 watts of line loss.  This would leave some 70 watts of available power from a 100-watt amplifier.

Assuming the use of lower quality 5-watt speaker-transformer combinations with transformer insertion loss of 1.5 dB, each speaker would consume 7 watts if tapped at the 5-watt tap.  Therefore, a maximum of 10 speakers could be connected before overloading the 100-watt amplifier (7 watts X 10 speakers = 70 watts).

To provide minimum power loss and the best low frequency transfer, Davis transformers are made using grain oriented steel for core material.  The result is "quality you can hear."

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