About Pre-Gain - Violectric HPA V222 User Manual

PRE-GAIN
These DIP-switches are situated on the back of
the unit.
Settings are made for the left and right channel,
they shall not be different from each other.
With these switches an additional gain or
attenuation may be set.
It is dependent on the output level of the input
source and the sensitivity of the headphones
connected. By this measure it is maintained to
achieve lowest possible noise and maximum travel of the volume
attenuator.
The high gain/attenuation range of +/-18 dB (factor 64) ensures a
perfect match to any source with any headphone in the market.
Too loud ? Too soft ? The PRE-GAIN method
The VIOLECTRIC HPA V222 is specially designed to drive
headphones. To do so it is placed between up to two analogue
sources and the headphones.
Headphones however can present load impedances from 8 to 2000
ohms and efficiency ratios from 85 to 115 dB per Milliwatt.
The sources may have output levels between 0.5 Volt up to 10 Volt.
Thus, it can be quite tricky to fulfil all demands, since...
... owners of high-efficiency headphones will rarely set the volume
control higher than 9 o'clock in order to exclude hearing damage,
while
... the maximum setting may still be too soft for low-efficiency
headphones, but
... all users expect highest quality at lowest noise and distortion.
circuitry
Thus, the must adapt itself - as the headphones won't do
and the sources will seldom do!
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User´s Manual HPA V222, July 2022, F. Reim