>I think 100uF caps is enough value. Look these plots (with 100uF in >AF-amp), > we see identifical plots for Line-out and for Phone-out. > > logarithmic view: http://forum.cqham.ru/download.php?id=43583 > linear view: http://forum.cqham.ru/download.php?id=43582 > > 73! Alex
Alex, The S/T FFT program you have allows the user to display in semi-log mode. That's the preferred way of looking at audio response. Resolution of low-end response will show much more detail that way, especially the area of interest below 200 Hz. Also, keep in mind that the choice in coupling cap value is wholly dependent on the load Z. When making response tests of the headphone output with the FFT program and sound card, try loading the headphone output with various values of resistance in increments starting at 8-ohms, working your way up to say ...50 ohms. You'll end up with an interesting family of curves that can then be saved in the S/T program. Using a sound card without external input termination often results in termination Z onto the circuit of only about 2K-ohm or so, depending on the model of the sound card. Pro sound cards (typically with XLR pig tails) have the ability to select various degrees of input Z. Paul, W9AC ______________________________________________________________ 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
