I'm trying to isolate and symetize an unbalanced input !

[Bombyx mori]

Hello,
Could you please, take a look at my schematic, i'm trying to isolate and symetize an unbalanced input.
I've forgotten the 100R and 100µF on the XLR outputs...  ;D

 

[Bombyx mori]

Hello,

100R and 100µF on the XLR outputs added...  ;D
You can click on the thumbnail.

 

[RuudNL]

IMHO you can at least omit one OpAmp stage.
(The signal at the output of the 'third' OpAmp is the same as from the 'first' OpAmp.
So you could do the same with only one 5532.

 

[Bombyx mori]

Thanks for your answer, i'm a tad sorry for my too evasive question, and you are not aware of the particuarities of the whole circuit and all components specifications.
The first buffer is here for the transformer optimisation , there is a counter reaction coil (the lower one) that lowers drastically the THD.
My question was more about the output buffer conception  and the utility (or not) to replace it by a that1646 or a DRV135 ?

 

[Bombyx mori]

The first buffer is here for the transformer optimisation , there is a counter reaction coil (the lower one) that lowers drastically the THD

In a Zero Field (ZF) transformer application, the magnetic field caused by the input signal is balanced by a feedback loop which includes the transformer's secondary winding. The feedback arrangement extends the low frequency range to almost DC in spite of the small size of the transformer.

 

[Harpo]

Circuit looks similar to http://www.hausverwaltung-heger.de/al_leck_trick/V475-2_Schematic.pdf.
Crosscoupled output stage (either by dedicated chip 1646,... or dual opamp 5532 with surrounding circuit) will work much better. Just imagine someone joining cold/pin3 with gnd/0V reference by wire or a TS plug that will short out the 1st. 5532.
(BTW, DC blocking cap (C3) seems missing in your schematic, just in case you don't have a gapped transformer)

 

[Bombyx mori]

Circuit looks similar to http://www.hausverwaltung-heger.de/al_leck_trick/V475-2_Schematic.pdf.
Crosscoupled output stage (either by dedicated chip 1646,... or dual opamp 5532 with surrounding circuit) will work much better. Just imagine someone joining cold/pin3 with gnd/0V reference by wire or a TS plug that will short out the 1st. 5532.
(BTW, DC blocking cap (C3) seems missing in your schematic, just in case you don't have a gapped transformer)

Thanks for you help (it gives me the inspiration that show me the right way)

The first stage is a zero field transformer application and i must use the manufacturer schematic.
For the second stage i've finaly opted for a DRV134 beacause its 10K input impedance seems perfectly matched with the first stage and its 50K output impedance is also perfectly matched with my amplifiers input impedance (typical 50K :) Oups !
I d'ont see any better choice for my application IMHO.

 

[Bombyx mori]

http://www.google.com.au/patents/US4614914

Here is the low distortion transformer coupled circuit patent, is there any transformer designed to operate with a negative impedance OPAMP please ?