TomW wrote on Sun, 11 July 2004 06:09
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I would be interested in developing this topology to make a 4-band EQ with passive low and high bands with some discrete opamp gyrators for the 2 mid bands.
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Could be too complicated for this sort of DIY project. Unless the discrete opamp only has 3 transistors!
http://www.forsselltech.com/schematics/Gyrator1.htmProbably better to use a real inductor for this project, as everyone knows they have more "vibe."
I discussed with B-rad two ideas for something like this. First, is a three band Baxandall with either IC or 990 size opamps. Probably too clean for the audience. Second, was just the old bog-standard buffer to passive 600 Ohm LCR network to make-up amp, probably fixed Q, but doesn't have to be. Tube construction is a little more painful, but at least they can be seen with the naked eye. PSU also costs more than with opamps.
In thinking about this, I was reminded of the old "saturable inductor" where you have in effect another input to the system. Used in ancient de-essers. Distortion is probably off the map. Can you cobb your own from existing parts, is the question.
This might actually be unique today, so you didn't hear it from me.
We can recycle those old Western Electric circuits untill the bovine return......
DC