Fred, We *were* talking about the K3 LINE IN (or so I thought). That uses a stereo jack, but is only connected to the tip. For those who need to convince themselves, plug a bare 3.5mm stereo plug into the LINE IN jack and measure the resistance between the ring and ground - you will find it is open circuit (nothing connected, and not grounded). The tip, however has about 640 ohms resistance to ground - that says that one can use an off-the-shelf stereo cable between the computer line out and the K3 line end without concern for either the computer nor the K3.
As for the K3 LINE OUT, that is stereo. The main receiver connects to the tip (left channel) and the subRX connects to the ring (right channel). If the sub is not installed, there may be some noise on the right channel, but no sound. The transformer coupling is assurance that no damage will occur if either of the line out channels is shorted to ground. So if one uses a mono cable here, it will cause no damage, but nothing will be heard in the right channel of the soundcard. Most computer soundcards will not be damaged by plugging a mono jack or a stereo jack with the ring grounded into the mic connector. Most soundcards use the ring to provide bias to the electret elements found in many computer mics, so they do apply a voltage to the ring, but it is through a resistor of a value high enough that shorting the ring of the soundcard mic connector should not cause any damage, but then I do not know the particulars of all soundcards - if you are concerned, consult the soundcard manufacturer (if you can!). 73, Don W3FPR Cady, Fred wrote: > OK, guys, here is the real skinny, from the schematics: > As shown on the K3 Block Diagram (6/6/07), The DSP RX section provides a > two channel AUX AF Out to the KIO3 board. This stereo signal is > transformer coupled (see KIO3 Main - Sheet 3) to the Audio IO Board. The > KIO3 - Audio Board does indeed show a stereo LINE OUT with the > LINEJACK_R on the ring and LINEJACK_L on the tip. The input side of the > audio transformers on the KIO3 board have series 600 ohm resistors. Thus > it is possible to short the ring to the ground (which worst case could > happen even by using a stereo cable between the K3 and a mono Line In or > Mic In on a computer, depending on the computer input circuitry and if > the computer and K3 grounds are connected). But, due to the transformer > coupling in the KIO3, you won't hurt the K3. (Probably) :-) > > Cheers, > Fred > > > Fred Cady > fcady at ieee dot org > > _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
