Violectric HPA V280 User Manual page 22

Instead of six problem zones we fortunately got not twice the issue but only
eight.
The signal quality rises because there is no common ground as well as there is
no load applied to the ground potential.
But it is not everything gold with a push-pull amplifier.
Beneath higher costs of a specific product because of doubling the components
there are the following points taken into account:
·
Double output impedance because two impedances per channel
·
Higher static noise because of double gain
·
Risk of more distortion because of two amps per channel
Using a push-pull amp as a headphone amplifier is most times not because
doubling the output amplitude. Especial when there are only low impedance
headphones to drive.
There is more than one amp in the Lake People / Violectric program range with
more than enough amplitude – even for high impedance loads.
So, what is the sense of a balanced headphone amplifier ?
As mentioned earlier a "simple" amp has the ground potential as its reference
point. To be more precise, it is not any point of the ground plane but the ground
pin(s) from the transformer. The output amplitude swings preferably
symmetrical around this reference point otherwise we would talk about DC
offset.
The theoretical maximum effective output voltage swing is calculated simplified
as follows:
Amount of the operating voltages
2 x (root 2)
Inside a "normal" amp a voltage is sent to the load (the voice coil of the
headphone).
This voltage is coming back via a common cable for both channels to the
ground contact of the headphone socket and from there to the foot-pin of the
transformer, the true reference point.
Because the wires from the headphone to the amp as well as the contact(s)
and the ground planes inside the amp don't have a resistance equaling zero but
resp. Amount of the operating voltages
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