This sort of outline concept for a balanced augmented configuration...

http://www.g4jnt.com/LFLoopAnt.gif

Not sure if the emitter centre tap needs to be decoupled to actual
ground.  If not, the whole amp is completely RF floating wrt the
ground connection.    The input certainly doesn't

Andy


On 16 December 2011 18:54, Andy Talbot <[email protected]> wrote:
>> But, looking at the circuit of the preamp in Figure 6, I'm wondering
> if, instead of what is virtually two independent input stages, with
> their own separate transformers, you considered a differential
> push-pull feedback as a single entity.   Have a centre tapped
> secondary in the bases (with the centre tap to AC ground),  but with
> the primary connected between the two emitters, ie directly across the
> loop input.
>
> The two input transistors now operate in true differential mode,
> rather than as mostly-independent amplifier stages, and with only one
> feedback transformer, complexity and wire losses are reduced.   This
> will give even more decoupling of the loop from ground.
>
> Andy
> www.g4jnt.com
>
>