[R-390] Headphone recommendation

[Charles Steinmetz]

Tisha wrote:

>What may be overlooked is that
>there is a frequency response to a transformer and that by taking a
>transformer that was intended for 60 Hz service and putting it to 300-3000
>Hz audio service is not going to give you ideal results.
>
>Looking at it simplistically, the winding ratio may be right but the
>performance will be sub-par. They are really going to roll off at higher
>frequencies.

I have measured many, many 12v power transformers and have yet to 
find one that does not respond within 3dB from 20 Hz to at least 12k 
Hz with ease at a 1 watt level (most go out to >20k Hz).  They also 
have much lower distortion than the detector and output section of a 
390 or 390A, as long as there is no DC in the windings (as there 
isn't in the application we are discussing).

There probably are 12v power transformers that do not exhibit audio 
fidelity (response and distortion) superior to that of the radio, but 
they must be rare -- I have yet to measure one.

Best regards,

Charles