I did work on some audio systems - half a century ago - so I'm no expert. We did use 600 ohm "line level" output for long distance lines (e.g. from a microphone mixer just off stage to the power amplifiers up in the projection booth in theatres). That might involve 200 or 300 feet of cable by the time the got from one place to another. The connection was made with a shielded and balanced line with - and this I assumed was the critical part in the 600 ohm specification - a 600 ohm center-tapped transformer at each end to suppress common-mode noise the line might pick up.
I thought it was interesting that Elecraft resurrected this application specifically to avoid noise pickup by the circuit traces within the K2 carrying audio. That's why the K2 has a fully balanced audio system until the signal gets to the LM-386 output I.C. The problem there isn't external noise, it's the abundant digital noise floating around inside the K2 that can easily get into the low-level audio lines. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
