[hpsdr] Question: Line out audio vs earphone audio

Ronald Cox w9kfb1 at mac.com
Wed Jan 14 20:52:23 PST 2009


 From Wikipedia:
"Line out

The signal out of line out remains at a constant level, regardless of  
the current setting of the volume control. You can connect recording  
equipment to line out and record the signal, without having to listen  
to it through the device's speaker, and without the loudness of the  
recording changing if you change the volume control setting of the  
device while you are recording.

The impedance is around 100 ohms, the voltage can reach 2 volts peak- 
to-peak with levels referenced to -10 dBV (300 mV) at 10k ohms, and  
frequency response of most modern equipment is advertised as  
20Hz-20kHz (although other factors influence frequency response). 
[citation needed] This impedance level is much higher than the usual 4  
or 8 ohms of a speaker, such that a speaker connected to line out  
essentially short circuits the op-amp. Even if the impedances would  
match, yielding the theoretical maximum power transfer of 50%, the  
power supplied through line out is not enough to drive a speaker."

Is there a place to get such a signal so digital modes can operate  
unaffected by the AF control on PowerSDR with Mercury. Maybe it is in  
the plan for the future?

Ron, W9KFB



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