Re: : K3 receiver noise questionable test results

Posted by Julian, G4ILO on Dec 19, 2009; 10:40pm
URL: http://elecraft.85.s1.nabble.com/Re-K3-receiver-noise-questionable-test-results-tp4192141p4192997.html

Joe Subich, W4TV-4 wrote

My tests with an audio spectrum analyzer using both broadband
noise and internally generated receiver noise show that the
K3 is flat from 100 Hz to 4100 Hz when using the 6 or 13 KHz
roofing filters with FC=2.10 and BW=4.00 to either speakers
or Line Out.  Headphone response is another issue that can be  
addressed with the Rev C/Rev D DSP assemblies or replacing the
10 uF headphone coupling capacitors with 100 uF caps and/or
using high impedance headphones.

I agree the line output is pretty flat which is why the MP3 files I tried to make didn't demonstrate the problem.

I think that rather than replace the DSP board I'll look for some high impedance headphones. But even with them, I still feel the sound on SSB needs some bass/mid range boost and a bit of extreme treble cut. I doubt if the headphones need anywhere near 100mW of output to drive them so overloading the amplifier should not be a problem.