[TenTec] Speaking of Headphones (Orion)

[Robert & Linda McGraw K4TAX]

In general, headphones that have a Z of more than 100 ohms will likely be 
ineffective on today's solid state radios.  The military "cans" which were 
designed to operate from a 500 ohm source, provided by those vintage 
receivers, have even more of a problem getting the level high enough with 
today's radios  They become voltage driven devices and with typically 13.8 V 
being available, thus the monolithic devices will only swing about 7.5 volts 
or so with very little current.  Lower Z phones in the range of 10 to 30 
ohms seem to do a really nice job and won't cause "speaker blowout" when 
unplugged prior to turning down the volume.

To the other end of the spectrum, phones that have very low Z values are 
thus getting into the current limit range by internal series R values placed 
in the output to protect from accidental shorts to the output stage.

73
Bob, K4TAX