Pro Audio Design Forum

https://www.ka-electronics.com/images/jpg/Dobrev_Biomedical_Practical.jpg This figure 3 is an odd bird, with my beloved 5 resistor bilateral current sources (using 6 resistors) as input loads. For normal (differential) inputs, those current sources look like high impedance, but for common mode sign...

I see the ancients have been busy, but 2005 isn't that old... I still remain apprehensive about tying a shield (antenna) to a virtual earth. I recall one mixer product where a bus inside a metal chassis made enough of an antenna to rectify some radio station, so connecting a shield, without passive ...

I am not very optimistic.. For a phono preamp you want a well defined input termination (47k+100pf?), and low noise. I guess you could hang a passive termination to ground at the lower input. This is probably not much worse than typical SE phono preamps. For (lead) guitars you like very high input Z...

I'm not sure exactly why I dislike this so much. It certainly fails my symmetry test. I'll try to ignore that and look at it as a SE receiver. While perhaps with biomedical we can treat inputs as currents or very high impedance inputs, For my world I deal in voltage sources, generally with parallel ...

I see two nodes labelled Vcm.

How does it look with CM stage defeated?

JR

If I were trying to find other things useful to do with THAT chips, adding two external precision resistors to a 1240 could turn it into a bilateral current source (or just add 5 precision resistors to a 741). But sticking to an all THAT all the time theme, here is a question for Wayne to ask his bu...

OK, I'm a little lost? Non-inverting sum? Rsource=10k? I think you got it. Rsource would be 10K build-outs from the channel. Whether it works with non-floating sources dunno. Seems like it should. I will try to keep this investigation in the context of console summing buses. Sources are not floatin...

I believe I could probably make a better analog summer than what is out there, but not better than a good digital summation. So what's the point? It's a little like making the best buggy whip. Tell that to the people that make them. And I belive that you don't think there's a point in exploring thi...

"Dobrev?" Summing (Mix) Amp Topology Using Common Mode Drive to the Reference Leg's Non-Inverting Summing Node. https://www.ka-electronics.com/images/jpg/Dobrev_Mix_Amp.JPG "Dobrev?" Summing (Mix) Amp Topology Using Common Mode Drive to the Reference Leg's Non-Inverting Summing ...

OK, if you are asking about sum buses, this I have spent some time thinking about. First there is a critical distinction between I/O and sum buses... I/O generally, (not always on the "O" side) only interface between two local grounds. Summing a multiplicity of signals requires dealing wit...