The benefits of this circuit are that all I/O's are balanced, and the output chips can be forced to run into an unbalanced input by grounding one side, if need be, without damaging the chip. This keeps the grounds floating between the mixer and the xmtrs (like a transformer), which may (or may not!) help keep ground loops at bay. Also, this circuit is DC coupled all the way thru and will pass a square wave. This means you can drive the inputs with highly processed, even clipped, audio and what goes in also comes out. Finally, having multiple inputs may be handy for some folks. If you don't want that, just eliminate the multiple input stages and gain stage.
Of course you could just use op amps to drive the rigs unbalanced, too. 73, Gary W3AM N0DBX wrote: > >Darrel: > > > >Here's a link to a schematic I just did of a mixer/distribution amplifier that > >would do what you want, and more: > > > >http://www.w3am.com/W3AMmixerDA.jpg > > > >Low parts count and excellent fidelity. All balanced I/O. > >Does this help? > > > >g > > TNX. We're getting in the ballpark. Still thinking and figuring what levels > I need for the various rigs, etc. Have found several ideas in the area of > Op Amps. Somebody did this a few years back and think it was in QST, > but can't find it. It was for modern transceivers, of course. I suppose it > would be easiest to tailor an amp for each rig and then tie them together > in the inputs. I'll study W3AMs data a little more. That site had escaped > my searches. > > I need a little gain on the main AM rig, but not on the new stuff. Gain would > probably make it easier to stay away from hum. The possibilities for ground > loops abound! I'm still rolling it over in my mind and appreciate the input. > > Darrel
