Paul Christensen: >> 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
Paul, of course you are right if we talk about Phone-Out, also on these plots you can see the graph from Line-Out. This out have to matching ideally with a sound cards. If we don't have needed LF from Line-Out, where it LF take for Phone-Out? 73! Alex ______________________________________________________________ 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
