Pro Audio Design Forum

I was impressed at the time because that quad cable was a relatively low cost change that delivered real performance benefits in practice. Yes it does. I remember some tests we did near dimmers. I think it was Canare and it was quite impressive and no more difficult to terminate. In making the elec...

I previously wrote: The common mode impedance, due to cross-connection of the inputs, is identical on each input leg. Not true. It's the differential impedance that is equalized by cross-connection on each input leg. Does this matter? I don't know. We report, you decide. Jung and Birt seem to think ...

My take is that the simple 4 resistor Diff amp (THAT 1240, 1243, 1246) with CGO caps & 1% resistors from the same batch gives superior results at low cost. Can't argue with that. I wouldn't have used the 1240 in the MS Matrix if it weren't the most precise. The balanced input impedance of the c...

I tried the "Fractional Feedback" circuit aka Sony figure 5 and it works pretty well. I used a lesser range ~+12 to -10 with a 10K pot. This places "0" almost near the center. As expected the CM rejection was not reduced since it's realized in the first stage. The control law of ...

It took me a few minutes to look up what's inside the 1286, but from a quick overview, that looks like it should present a nice symmetrical input Z, for balanced line inputs, we have no use for balanced dual audio signals inside most of a console, so in practice there needs to be another diff stage...

Going through some old posts I found this thread started by juniorhifikit: https://www.proaudiodesignforum.com/forum/php/viewtopic.php?f=6&t=359 His original schematic link is broken but I believe that the topology being discussed was from the SSL 82E149 Line Input: https://proaudiodesignforum....

I submit that if this is a very small fraction of the Tracking Force, it can be ignored.

OK, that makes sense.

My point in posting this was that no one really "invented" the SuperBal circuit. It appears to have a long, long history. Credit should be given to someone for the name though. :geek: I tend to agree with your conclusions. Though not variable gain, one advantage of the "Birt" bal...

If you take Morrison's 1964 single-ended example and make it a fully differential input, it becomes the symmetrical 1971 Burr-Brown circuit. It's a vertical mirror-image. The only thing that's not mirrored are the "sense" and "reference" connections of R1 and R1'. One goes to the...

I'm with you up to the philbrick fractional feedback example.. is that related? Or just a piece of the variable gain bal input. Thank you for asking. Follow me here from Morrison (1964) to Burr Brown (1971). This is Morrison single-ended variable gain stage re-drawn to look more like the Burr Brown...