Rather than add another veer to the differential thread, here is a different veer in a different place...
We've engaged on this point before and I am not a fan of fully differential paths inside gear. For simple paths, it generally doubles the cost while providing little benefit over a single ended path. For more complex circuits the degree of difficulty and cost way outpaces any benefit.
These ICs seem to have a fairly specific area of application..
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That said, in the spirit of all differential all the time, here is a circuit I scratched out (but never melted solder over) several years ago. My desire was to make a DC coupled differential in/ differential out level shifter, so I could float a discrete DC coupled mic preamp front end gain stage up to phantom voltage levels and shift it's output down to the nominal 0V DC for interface with other gear. (I guess most would just use a transformer for this, but I consider transformers as little better than capacitors, on my list of components to avoid. )
This simplified schemo does not show the actual front end preamp gain stage, just the level shift from nominal 50V DC down to 0V DC.
Basically it's a DDOA with 3 device LTP input, with T3 and T8 looking like inverting opamp inputs relative to T7 that acts like a common non-inverting input. FWIW this looks like it passes the two legs intact, albeit inverted and level shifted. CM signal does cancel.
Caveat- this schemo is simplified and unproved so may not even work,,, I never bothered to develop it further, since it seems an even better idea would be to float an A/D converter up there to the phantom voltage level, then use optical or whatever to level shift the digital output down to the real world.
JR
Samuel Groner said:It's a pitty that there are not more fully differential opamps suitable for audio around; particularly for mic preamps and converters, where there is a fully differential signal path from input to output, they are of great use.
Samuel
We've engaged on this point before and I am not a fan of fully differential paths inside gear. For simple paths, it generally doubles the cost while providing little benefit over a single ended path. For more complex circuits the degree of difficulty and cost way outpaces any benefit.
These ICs seem to have a fairly specific area of application..
=====
That said, in the spirit of all differential all the time, here is a circuit I scratched out (but never melted solder over) several years ago. My desire was to make a DC coupled differential in/ differential out level shifter, so I could float a discrete DC coupled mic preamp front end gain stage up to phantom voltage levels and shift it's output down to the nominal 0V DC for interface with other gear. (I guess most would just use a transformer for this, but I consider transformers as little better than capacitors, on my list of components to avoid. )
This simplified schemo does not show the actual front end preamp gain stage, just the level shift from nominal 50V DC down to 0V DC.
Basically it's a DDOA with 3 device LTP input, with T3 and T8 looking like inverting opamp inputs relative to T7 that acts like a common non-inverting input. FWIW this looks like it passes the two legs intact, albeit inverted and level shifted. CM signal does cancel.
Caveat- this schemo is simplified and unproved so may not even work,,, I never bothered to develop it further, since it seems an even better idea would be to float an A/D converter up there to the phantom voltage level, then use optical or whatever to level shift the digital output down to the real world.
JR