Violectric HPA V 100 User Manual page 20

Moreover, its structure has the advantage of thermal coupling between its
internal components. Also ageing issues play a much less important role.
Due to the large number of op-amps types offered, it is possible to pick
an optimum type for any specific application.
Why does PRE-GAIN make sense ?
Two extreme examples (with the HPA V100 at 8dB gain, volume control
set to full):
1st example:
The (pre-)amplifier provides 4V output voltage, whereas the headphone
requires only 2V for 100dB sound pressure level.
With the control fully turned up, the V100 would deliver 10V output at 8dB
gain. Therefore the volume control would have to be operated very
carefully in order to avoid hearing damage. Moreover, any interference at
the input should be avoided since it would be "unforgivingly" amplified as
well. With PRE-GAIN, the input level can be reduced by 12dB (a fourth),
with 1V instead of 4V as the result. This 1V is again amplified by 2.5, then
equalling 2.5V. Now the volume control can be turned over almost the
entire range.
2nd example::
The (pre-)amplifier provides 1V, whereas the headphone requires 20V to
release 100dB of sound pressure.
With the volume control fully clockwise, the V100 would provide 2.5V at
8dB gain only - much to low for the headphone. By means of PRE-GAIN,
input level can be boosted by 12dB (four times), resulting in effective 4V.
These are again multiplied by 2.5, now equalling 10V. This is still not
enough, but far closer to the optimum value: The headphone achieves
114dB sound pressure level.
Your HPA V100 may provide a USB input as an option. It has priority
over all the other inputs and mutes these when a valid input signal is
detected. Since the HPA V100 is a terminal device after USB
regulations, it has a type-B interface.
Which USB devices can be connected to the HPA V100 ?
Connections can be established to tabletop or laptop PCs. MP3 players
or similar gear cannot be connected.
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