Hi Scott Out of curiousity, on the headphone output, are you running it directly into a sound card to use SpectrumLab? Or do you have some amount of resistive load on the audio output with measurement across the load? 73, Bob N6WG
----- Original Message ----- From: "Mike Scott" <[email protected]> To: <[email protected]> Sent: Monday, March 02, 2009 9:36 AM 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 ______________________________________________________________ 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
