I would guess that the headphone output is expecting a low Z (~16 ohm?) termination, and your sound card has a high Z in. Try a terminating resistor across the headphone jack in parallel with your sound card.
Just a guess. Dave Hachadorian, K6LL Yuma, AZ ----- Original Message ----- From: "Mike Scott" <[email protected]> To: <[email protected]> Sent: Monday, March 02, 2009 5:36 PM Subject: [Elecraft] K3 Audio out artifacts >I have been investigating audio artifacts in connection >with the K3 AGC hold > experimental firmware. As a reminder, I live in a high > noise area. > > As part of the investigation I have been looking at both > Line Out and > headphone audio using Spectrumlab on my PC. > > I am finding substantial 60-hz contamination on headphone > audio that I do > not see on Line Out. > > On Line Out I see what looks like fairly clean audio with > donor lines at > 2400 Hz and 3600 Hz outside the rx filter pass band (1 KHz > DSP filtering). I > presume these are the 40th and 60th harmonics of 60 Hz. > They are 50 dB below > noise background noise. > > With only a change of where I plug the PC audio cable > (moving from Line Out > jack to rear headphone jack) the audio looks quite > different. > > Now I see a whole array of 60 Hz artifacts. The 3rd and > 5th harmonics are > about equal to comfortable listening level audio. As I > look higher in > frequency the harmonics generally reduce in level but only > to about 20 dB > below comfortable audio listening level. There is also a > broad artifact (300 > Hz wide) at roughly 3300 Hz that is also 25 dB down. > > The artifacts do not go away with reduced volume control > settings but remain > a constant feature of headphone audio out at any setting. > > Is there something about my test set up that I do not > understand? > Does anybody else see contamination of headphone audio on > their K3? > Could there be something wrong with my K3? > Could transformer coupling (Line Out) vs direct coupling > (headphone) be > adding something to my test set up that I am not factoring > into the problem? > > > I have never quite believed the audio of my K3 was like > Wayne says it should > be but can make it better using slow AGC (separate post), > I doubt that has > anything to do with the artifacts I see here. > > > Mike Scott - AE6WA > Tarzana, CA (DM04 / near LA) > NAQCC 3535 > K3-100 #508 / KX1 #1311 > [ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
