Balanced quasi-floating output

[xocoatl]

Hi guys!
I've just found intereting output circuit on Douglas Self's page about balancing . And I think about using it in my preamp. But as I look on it , as I is drawn below, I'am not sure if it'd work like it should. Which do yuo think OPAMPs (or are these finite/low gain amps) inputs are + / - ?



I searched google and this forum with no success.

[Stocker]

reminds me a bit of the front end of a citation 16 schematic.... At the least it's unusual, at best you might like the way it sounds!

[ThorstenL]

Konnichiwa,

Originally posted by xocoatl
I've just found intereting output circuit

Actually, the circuit is not entierly complete. A complete one is here:



In that case it is best to generate the balanced drive by using a further Op-Amp in inverting unity gain configuration. The same circuit can be adapted to Single ended input, here an example from a circuit used in a Behring Digital X-Over:



That one is of limited value for actual use, as the gain is below unity, but it illustrates the requiorements for unbalancing the resistors with single ended drive.

The first circuit shown together with added inverting Op-Amp on a chip is readily available from TI/Burr Brown as DRV134 and from Analog/SSM as SSM2142 all integrated onto a single chip.

Personally experience however suggests that despite the extra cost a high quality line output transformer (Stevens & Billington TX410LO for example) is a better choice, if sound quality is of concern.

Sayonara