[Hallicrafters] SX-42 Phone Jack

[HallicrafterSX28 at aol.com]

Hi
If you look at the schematic ,the headphones are driven by the   voltage 
amplifier 6SL7 tube ,not by the final power stage.So for satisfactory  performance 
the headset should be of HIGH impedance. It is interesting that on  the the 
SX-28 the headphones were driven by the final power stage which gives  more 
volume in the headphones.But then for some reason only known to  Hallicrafters 
Engineers they reverted back to the headphones being driven by the  Audio 
voltage amplifier as was done on the models preceeding the SX-28. So if  you have a 
high impedance headset ,and volume still sounds kinda low that is  typical.
In fact on my Sx-42 I modified the wiring so that the headphones are driven  
by the 500 ohms output which is a perfect match since the military headset I 
use  is also rated at 500 ohms.
Nick



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